So, good morning, everybody. You sleep well? Nice sleep? Okay. And this lecture is about calderas, okay? So we are going to see the structure, the evolution and the arrest, as well as the magma transfer processes within calderas. So I will just start with a quite provocative slide. This is a Google Earth view of the Neapolitan area. And you see this dark spot here. You know what is it? It's Vesuvio, right? And you know Vesuvio is famous for its, mostly famous for its Pompey eruption 2,000 years ago. And Pompey is somewhere here. Of course Pompey was there 2,000 years ago. And today there is no Pompey, but we have Naples today, which is on the opposite side of the volcano. And of course there is a significant treat on the town by the volcano. So I would just like to show you a very down to earth hazard analysis, considering the possible impact of Vesuvio on Naples. First you have to think that Vesuvio is downwind with regard to Naples. So all the products will fall to the east, very likely. Then if you look at the most destructive eruptions, they are in the order of one cubic kilometer. Thanks a lot. And then you see that the volcano, since 1944, it has been quiescent. So no degassing, no seismicity, no surface deformation. On the other end, on the other side of Naples, to the west, we have this volcanic field. And this is Campi-Fermeri caldera. So it's a caldera. It doesn't have any prominent topographic fissure. In fact it's very difficult to distinguish that it's a large volcano. And indeed if you go here in the middle of the caldera, the people will ask you whether they are safe from Vesuvio. No, it's true. You have to consider also that the caldera is upwind with regard to Naples. So the products will most likely fall on Naples. And then the most destructive eruptions were larger than 100 cubic kilometers. And then finally on top of this the caldera has been restless in the last 70 years, 60 years. So this is just to say that we should pay a lot of attention when we deal with volcanoes. There are some volcanoes which are really not so evident as we may expect, but indeed they are very, very dangerous. So the message is that these are large, long-lived and restless magmatic systems which are systematically responsible for the most destructive eruptions on Earth. So I guess this poses an additional care when we study volcanoes that these systems are very delicate to handle, I would say. So caldera is defined as a subcircular depression with a diameter which is usually larger than that of a crater. And the most important part is that it involves some removal of magma from the reservoir. This may occur to an eruption or also in many cases through the lateral intrusion of magma at depth. And of course, which is the most distinctive feature of a caldera? A feature you will be able to recognize very easily is the topographic beam, which is a morphological feature because this lies well outside the structural rim where the ring fault is, and the ring fault is responsible for the subsidence of the central part of the caldera. So what we usually see is just the erosional part of this ring fault, and then the ring fault is usually valid. Hidden. And you may able to recognize it if you're lucky if there is some vent just above it because the magma is intruded in the ring fault. Then inside the caldera, many times you may have an uplifted area even of one kilometer over long time scales in the order of several thousands of years. And these are resurgence. So this resurgence exposes the intercaldera igrimbrite as well as any sedimentary deposit within. So this is the established classification of caldera which has been proposed. And this is based on million field evidence. And these are five types, five end members, I would say, of geometrical features of calderas. I don't know how much you know about this, but this is a very simple type. It's called a pistol because it's a coherent block which is subsiding. This is a piecemeal where you have different blocks which are collapsing. The trapdoor is an asymmetric structure with some flexure on one side and the ring fault. Well, actually this is not a ring fault. A fault because it's not all around the caldera. A fault on the other side. A down seg is a, well, less pronounced caldera. It is characterized by a broad flexure at the surface. And then we have a funnel which is a very narrow and deep caldera. So just look at these five types of caldera here and think which may be the most suitable to explain, for example, this caldera here which is not far from here, it's in central Italy, Bolzena, this is the map view and this is the section view. So which types of caldera would you think may fit with this structure? Well, okay. I think there is plenty actually trapdoor. Yeah, it's a possibility, but of course this structure looks like a piston. Okay, so the central part may resemble a piston. On this side we have a down seg, so we also have some down seg component. On the other side here, which is here and here, we have lots of faulting, so it may be a piece mill. But yeah, maybe the overall structure is a trapdoor. So if you want to make all these a piston like caldera with a down seg dream, a piece mill dream and an overall trapdoor structure, which is too complicated for me. So you see, in this case we are not really able to explain the structure of this caldera just using these five, the simple five geometric types. And this is not just because this caldera is difficult to be understood. There are many calderas which are like this. Actually, possibly most of the calderas share this complexity. And then there is another problem which is about wing faults, the nature of the wing faults. Cindy was talking about tabo in New Zealand. This is, well, a very simplified structure of tabo from grammometric data in map view and in section view. And you see that the caldera here is bordered by these inward dipping faults. These are thought to be normal faults because of the displacement. And we have a similar stuff here also in bias. If you see the subsurface structure, all these faults here are inward dipping normal faults. And of course nobody has ever been there, adept to see that those are normal faults. I guess in most of the cases we were able to think that these are normal faults because you have a drill or you have this layer which is here, in another drill or the layer is up here, so you just put some normal fault in between. And you know why? Because this, I think this is something which volcanologists have been relying on a lot in the past because the idea is that if you have magma, if you have a volcano, you must have magma. So you must accommodate the magma in the crust, so you need extension to accommodate the magma in the crust. So if you need extension, the normal fault is the best candidate to have this extension. But of course there is a room problem, a space problem here. Do you know it? For example, look here. If you want to collapse the central block, if this has to go down, what happens? You must extend to the sides. Otherwise this will not go down. And of course this depends on the deep of the faults, but if you have a collapse in the order of 1,000 meters, maybe this is as deep as 2,000 meters, then you need to have a few hundreds of meters of extension. And if the collapse occurs in one day, today as it's usual, then you need to extend the crust of hundreds of meters in days, which is completely unrealistic. So you have this important space problem with this inward dipping normal faults. Some people have been wiser, and so they were drawing the faults in a subvertical geometry, so this doesn't make any problem with the space problem, which is of course feasible. And other people have been more provocative. They were drawing the ring faults like this, outward dipping. And these outward dipping ring faults imply which type of kinematics. If this is the outward dipping and this goes down, it's an apparently reverse kinematics. And many volcanologists are quite scared about this reverse component, because they think that there is some compression, so this means that their magma cannot make it to the surface. So many people really do not accept so much this model. So at this point, I hope you are sufficiently confused to ask yourself the same questions, which are here. The first is how can we use this established caldera classification to interpret the structure and evolution of calderas. And the second is which is the nature of the ring faults bordering the caldera, and in particular how can we solve the room problem. So we go to the first part of the talk, which is concerned about the structure and the evolution of calderas. You know what is this picture? This is an earlier view of Miyakej Jima, caldera in Japan, which collapsed in 2000, and you can clearly recognize an innermost ring fault here, and an outermost ring fault. We will see this in more detail in a few slides. So the first thing I did to try to understand something about the structure and evolution of calderas is, of course, to go to the field. I tried to go to some nice, well-exposed calderas, not so much like Campi Fregre, where there is a lot of sea, there is a lot of post-caldera activity, a lot of people, a lot of buildings. So if you go to these very peaceful places, you may try to understand something about the structural calderas. But even actually in the best conditions, like this caldera here, where there is no vegetation, there is active, there are two lava lakes, well, actually now there is one lava lake here, but a few tens of years ago there was another lava lake here, so it's a very active caldera. Even in these very favorable conditions, you can just appreciate the shallow morphology, not even structure of the caldera, and you cannot say anything about the deep structure. And so you have a sense of frustration if you want to really understand how calderas work on the field. I try to use analog models. They are very simple and they are very, very simple. It's a good tool, and you can really understand the processes behind with these type of models. So I started to make these models. This was a long time ago, and the funny thing is that at the same time many other people were doing the same models, and we didn't know about each other. And then when we compared our models, we saw that all the results were very much consistent. And this was independently of any boundary conditions. We had different materials, different apparatuses, different boundary conditions. Everything was different, but the results were very much consistent. And I guess this is a very strong point, because if you have different boundary conditions in your model, and all the results are the same, it means that maybe there is something you should think about. Maybe the models are not so funny as they might seem. And so I'm going to summarize here the structure and the evolution of all these models. And this is just depending on the amount of subsidence. So at the beginning, if we have a very low amount of subsidence, we develop a down seg at the surface. This is stage one. And the down seg results from the upward propagation in the ring folds, which are still buried at depth. So when the ring folds reach the surface, we have a scarf. And this scarf is the result of an outward dipping reverse fold. So those people were right maybe they were right in pointing out this outward dipping reverse folds. And stage three then, if we further increase the subsidence, we develop an outer, which is related to the upward propagation of these peripheral folds. And when these reach the surface, sorry I have some problem with when these reach the surface, we develop an outer scarf so that we have two concentric ring folds. And the outer most here is an inward dipping normal fold. So while the inner most ring fold is actually we will see is the mechanical explanation for the formation of calderas, the outer most normal fold just results from the collapse of this wedge here, which is unsupported during the subsidence of this central block because this goes down so this has to collapse and it collapses with these normal folds. So now you may wonder which is the reason to have these reverse folds here. There is no compression actually, it's just a matter of a differential vertical movement. So if you have this type of movement this may be a caldera the flow of a caldera, which goes down then the sigma one trajectories are not vertical but they are archuate and so the result is that you need a fold at a low angle with these sigma one trajectories which must have this geometry and these kinematics. So you end up with a reverse fold which has nothing to do with compression. So I guess volcanologists can relax about this problem. The only minor difference I would say it's a minor difference for me is the results from the thickness of your over burden. If you have a very thick roof overlying your magma chamber your experimental magma chamber then you just have a repetition of the same features you see with a thinner roof. This is the first set of outward dipping reverse folds and then when they meet you develop another one and then you may develop another one and then outside you have these normal folds. But you see this is just a repetition of what you see here so it's nothing new actually. So of course this is all very nice and it may be interesting but which is the feedback from the field or from geophysical data are these structures realistic in maybe all the modelers have made the wrong move together. Actually if you go to the field the problem is that before you make the models you have a certain view then you make the models you start to have ideas and you start to look for those data on the field and actually you see that there is plenty of evidence for it and people have usually neglected it for decades. So this is for example this is the map view and this is the section view of a pit crater somewhere in Nicaragua and this section exposes the deeper part of this pit crater and you can see that there is plenty of outward dipping reverse folds and outside we have some subvertical or inward dipping normal fold which is very similar to the experiment. Of course this is a pit crater it's not a caldera but the collapse mechanism is absolutely the same. If you look at the the distribution in some calderas like for example Rabaur here is one edge or the caldera here is the other edge or Pinatubo like in 1991 this is the seismicity which was developed during the 1991 eruption you see that the seismicity is focusing along these outward dipping folds. Here the folds maybe are too deep they were just meeting at the surface so this may explain why the Pinatubo caldera actually is very very narrow. But probably one of the most interesting pieces of evidence for this for the presence of this type of structure also in nature is the Miakezima collapse in 2000. This is a geological map which is derived from the picture I showed you before you can see we have this inward this inner ring fold the outer ring fold and if we make a section that also studied this eruption you can see that this inner ring fold is an outward dipping reverse fold whereas the outer most ring fold is an inward dipping ring fold so this is very much consistent with what we see in the experiments and it's not just Miakezima but we have a very similar structures developed also during the other caldera collapses which have been occurring during basaltic volcanoes in the last decade like in Dolomje in 2007 or even in Iceland in 2014 so at this point we see that there is a consistency between what we see in the experiments and what is there in nature so at this point if this is true we may try to make a further step we can say okay let's try to see what we have at the surface which is the structure of a caldera at the surface and try to extrapolate using the models which may be the structure of the caldera adept so for example if we have a down seg of the surface we can see that there is a a fault which is adept which is propagating upward and this doesn't have reached yet the surface or even if we see two pairs of nested calderas sorry, a pair of nested calderas we can think that we have an outward dipping reverse fold and an inward dipping normal folds so just looking at the structure at the surface we can try to say something about the structure adept using the models so in doing this here we listed all the calderas all the best known calderas with their diameter their amount of subsidence and in particular we assign to each of these calderas here a stage which corresponds to one of the four stages which we see in the experiments so for example miagezima is a stage four caldera because it develops the two ring folds and if we plot all of this on a diagram this is the subsidence and this is the diameter and you can have different type of stages with different colors all of this may look chaotic at a first glance but actually if you help yourself with some lines which should be interpreted as broad transition zones not sharp boundaries you can see that usually below this line we have a stage one calderas down sex here we have a stage two calderas here we mostly have a stage three and here we mostly have a stage four so this means that despite of course some discrepancy because nothing is ideal in nature if you have a fixed diameter of a caldera and you just increase the subsidence so you pass from stage one to stage two to stage three to stage four calderas which is exactly the same as we observed in our experiments so this means that this apparent random distribution of the structural calderas as an explanation based on our models which is essentially for a given diameter a function of the amount of subsidence so there is a continuum in these evolutionary stages which is defined by the ratio between the diameter and the subsidence so the lower is this ratio the more evolved is the caldera and actually we may also try to go further because if we have this diagram here once we have a certain amount of subsidence for a caldera with a given diameter we just may try to infer its structure without even looking at the caldera that's a bit extreme of course but it seems to work with for example with the Bardarbunga caldera which was formed in 2014 and I guess that toaster will say something about this in the next hours Bardarbunga had collapsed in the other 65 meters the width of the caldera is 7 km and so this would place Bardarbunga here in the stage 1 calderas in the down-seg calderas and according to the models they also interpreted the formation of the caldera as a down-seg where the ring folds at depth they didn't make it to the surface because the deformation was the subsidence was too low to develop the folds up to the surface so at this point you may also try to understand that and choose these experiments as well as their comparison to nature for an updated classification of calderas which just not takes into account only the geometric features of the calderas but it also takes into account the structure and mostly the development the evolution of calderas and this is just using the amount of subsidence for a given diameter passing from stage 1 to stage 4 the difference between this classification is almost like looking at an image in one case and looking at the movie in the other case so we may go back to Bolsena and rather than saying well, Bolsena is what did I write here asymmetrically collapsed piston type caldera with down-seg and piece mill rims actually it's just an asymmetric stage 3 caldera because it fits somewhere here in the previous diagram and we also use these models to try to understand something about the kinematics of collapse and to do this you can use this particle image velocimetry technique which tracks the motions of your particles on the surface of the model and in section view for example this is very high aspect ratio caldera and what you do you just there is a glass and you can track the motion of all the particles which are subsiding along this vertical line here from the surface to the depth and you can track this motion from the surface to the depth as a function of time and so you end up with different amount of well different rates of collapse so you can have some velocities and you can distinguish different types of collapse like a continuous collapse here the velocity is pretty much constant and it is similar to the one which is the same actually to the one which we impose at the base of our sand pack because in this case this is sand but then you may develop at one point some sudden collapses where the velocity may increase up to four orders of magnitude just keeping our source at a constant subsiding velocity and then after this over in a background of constant, quite constant collapse these dark blue areas you have spikes of higher velocities which give you an incremental collapse and this occurs when you develop the ring folds and you have some friction along the ring folds and this incremental type of collapse is very much consistent with what we see in nature in the last the last collapses for example at Miagezima again or Dolomje using the tilt data like this is Miagezima and this is Pitonella for next or even the seismicity data so this is interesting because in this case you may even be able you have some more quantitative results and you may even be able to match your experimental results with geophysical data which support in both cases an incremental collapse of calderas usually do not collapse in a continuous way but they collapse step by step so now let's talk about the second problem which is unrest unrest at calderas is a very important and delicate topic and I don't know if you are aware about unrest unrest can occur at any volcano and this is a deviation from the baseline in the geophysical and geochemical indicators so it's usually highlighted by surface deformation gassing, gravity changes and seismicity this may be related to the activity of the magma chamber or even if you are below calderas you usually have another thermal system which may also be active and may also complicate your understanding of what's happening the important point is that the unrest can be eruptive or not this means that every eruption is always preceded by an unrest but not all the unrest episodes culminate in an eruption so unrest is unnecessary but not sufficient condition to have an eruption and the biggest challenge of volcanology is when you are in an rest is to understand whether this will lead to an eruption or not this is the challenge that volcanologists have to face in the next decades so this is a cartoon this is just simplifying things this is a possible way to develop an unrest to trigger an unrest but it's not the only way of course in this case you have the placement of some shallow magma this is deforming the hostrock so you have seismicity fracturing the fracture may increase the permeability of the hostrock so you may have that the the magmatic gasses go up and fill the thermal system may also induce air quakes and induce surface fracturing with a net result to have degassing surface deformation and also seismicity at the surface so there are different types of arrest I'm going to show you just some very basic type some reference type this is from Marco actually you can tell this much better than me actually this is a typical unrest episode of a basaltic caldera and what you have here the deformation on the top of our caldera is given by this red dot c you have inflation, then you have the eruption you have a sudden deflation and then you continue with inflation then you have eruption, sudden deflation and then inflation again this is something which has been already shown by Paul and Michael the second day and I guess it's a very typical pattern of many basaltic calderas there will be some complication which is related to the seismicity accompanying this deformation if the magmatic system is open you will not see any seismicity or you will see minor seismicity because you really don't need to fracture the ostrok the conduit is open if the conduit is closed you will have much more seismicity so this may be some difference in basaltic calderas but the situation is much more complex in felsic calderas so this is an example from Campi Fregre you remember Campi Fregre and you can see from the surface deformation that since 1950 the early 50s we have at least one, two, three and four uplift episodes four unrest episodes and this one in particular in the early 80s has been quite intense you had two meters of uplift in two years with a lot of seismicity strong seismicity and also some important degassing and now the current unrest is more subtle well at least the uplift is more subtle, gentler and we only have 30-35 cm within the last ten years we have minor seismicity but we have a lot of magmatic degassing so as you may understand civil defense is very much worried about the possibility of an eruption at Campi Fregre today because of these fissures here what do you think about this? any idea? you may wonder there was nothing here, no eruption when I had two meters of uplift a hell of seismicity so why should I worry now that we have just a few tens of centimeters of uplift and no seismicity so this may be something which tells you to relax not to worry too much of course this may be true but if you look at Rabaul what happened at Rabaul? exactly on the same years in the early 80s where we had the unrest at Campi Fregre we also had an unrest at Rabaul with approximately one meter of uplift and then a very strong seismicity then after this we adjust well stable ground level without so much deformation very minor seismicity and then after a decade in the early 90s we had some minor uplift 20, 30, 40 centimeters no more than that with some minor to moderate seismicity and then at this point the galdera erupted and it was a bi4 eruption so it was not really a minor eruption so this is quite I would say non-linear and you had a helier and nothing happened and you just had a minor perturbation of your system here and this was leading to an eruption the possible explanation behind this is that you don't have to think about unrest episodes as separate entities so you should look at the cumulative history of the galdera here so this unrest episode was probably priming the system while this one was triggering it was just a so here the magma chamber was really getting somehow the magma chamber the intrusion was getting to shallow levels and so you just needed a small trigger to induce the eruption so you may understand how important and how delicate is to study the unrest processes at galderas and there has been this important very important monography by Newell Zulithin about unrest at galderas it was a review about all the unrest processes which have been occurring before 1988 so we tried to update these unrest episodes the knowledge of unrest episodes after 1988 so we created the database with all the available data on unrest instrumental unrest episodes after 1988 and we were able to identify these 66 unrest episodes from 42 galderas which have been quite well monitored in the last decades of course this is just a small part well not as much it's a part of all the active galderas which are around in the world but many of them are not monitored so you really don't know whether there's been an unrest or not there in the last decades you don't have any information but the fact that in these 42 galderas we were always able to see at least once an unrest in the last 25 years suggests that also the other galderas may have experienced some form of unrest and this also suggests that the unrest may be the rule rather than the exception at galderas and in this case most of the unrest episodes were eruptive and most of them occurred at mafic galderas so we try to to identify some types of galdera unrest in our first qualitative approach just considering the composition of the magmatic system very roughly mafic or felsic and then the amount of opening of the magmatic system so plug galdera means a galdera which doesn't degas semi plug is a galdera which degases and open galdera is a galdera which degases and has an open conduit to the surface so you see that these mafic galderas they are mostly characterized by eruptive unrest as we saw before so this means that there is a frequent release of magmatic eruptions and this may occur with a typical pattern you saw before so inflation, eruption sudden deflation and again inflation the only obvious difference being the presence of seismic or not so that in plug galderas so you expect some seismic whereas in open galderas you don't expect seismic the situation is more complex as we have seen with felsic galderas we have a more complex behavior the release of magma through eruptions is much less common and in many cases we have this hydrothermal system which is complicating your understanding of the galdera sometimes it's buffering the signal the magmatic signal sometimes it's amplifying it we were able to define two main behaviors one is for plug galderas so non degassing galderas these are usually smaller actually we have very few examples of this type of galderas pinatubo may be the best example even though there was not an evident galdera on pinatubo before 1991 pinatubo is half way between a stratovolcano and a galdera I would say in this case we had isolated and rapid unrest episodes whereas in the other case in the other category which includes most of the galderas and these galderas are degassing galderas they are usually larger and they are continuously restless over decades or in some cases over centuries and a nice feature is that these galderas are usually associated with resurgence so this is the relationship between all these features should be better investigated also to understand resurgence of course all of this is very qualitative so we tried to do a quantitative analysis so a statistical analysis of this data and I guess this has been done with Laura Sunday and I guess this analysis is pretty much finished now so I'm just going to anticipate some result very briefly in a very short way I guess one of the most interesting results is that the eruptive arrest is shorter than the non eruptive or failed if you like unrest so this means that if a magma is ready to erupt during an arrest it will erupt soon and soon means within a very few months is this blue frequencies here if we wait too much it will probably not erupt and in particular in non open calderas so this means in calderas which are degassing or not degassing so they don't have an open conduit we see that this short eruptive arrest is always accompanied by high seismicity and degassing and you may think this is complicated maybe not useful but just think about the ongoing arrest episode the ongoing arrest episode has been lasting for years maybe a decade and it has just some minor seismicity so if we should use this data and we want to really say something so we can if nothing changes in the while we may expect that the caldera campiferae caldera should not erupt in the near future we don't have high seismicity and the eruptive arrest is much longer than the one which is shown here to erupt of course this is a very simple analysis because it's just describing behaviors but what we have to do is to understand the processes behind so I guess this is an important the first important step to update that to understand how things may work in nature and then based on this we can try to develop some model which is trying to explain these observations some physical model so once you have an arrest there is usually some magma ready possibly ready to make it to the surface so you may expect to have some magma transfer so the next chapter here we will talk about the transfer of magma within calderas and you have seen on the other day the lectures of Claude Jopard and he was talking about loading of volcanoes so loading the role of topography actually with calderas we have the same problem what the opposite sign we have the unloading because we are removing mass we are removing crust so we may expect to have some some similar process but with an opposite behavior I would say and I guess actually that this unloading may be very important in controlling the stress distribution within a volcano and ultimately to control the path of magma transfer so as an example of unloading I will show you two processes two cases in one case we will consider a larger unloading which is given by a mafic caldera like Fernandina and in the other case a smaller unloading from a felsic caldera campiflegre so Fernandina is particularly interesting because it's quite a unique volcano because it develops these circumferential fissures outside the caldera rim and then which are here these black ones and then outside we have these radial fissures and these fissures have been observed only at very few volcanoes and these are mostly in the Galapagos islands so the problem is to understand this complex eruptive pattern and we have to think that below which fissure there is a dike so this means that we are talking about dike propagation, shallow dike propagation here and there have been many models trying to explain this but we believe that the most comprehensive model which is trying to explain all the observed fissure is the one which takes a loading into account this is a study we have been doing in the Eleonora in Marco and here we report these are results from a numerical model this is the topography of the volcano along a Nazi axisymmetric section from the center of the caldera, outward and this is the topography again, this is the caldera area and here we are just considering the stress distribution which is related to the topography, to the topographic variations so these dark lines that's a sigma 1 and the gray lines here is the sigma 3 and you can see that below the caldera you have, just below you have a subvertical sigma 3 whereas if you move to the side this is better showing this schematic diagram if you move to the side you tend to have sub horizontal sigma 3 distribution so this suggests that below the caldera you are promoting the placement of seals because sigma 3 is vertical and as far as you go to the side you are promoting the placement of incline sheets and then of subvertical dykes which in three dimensions are circumferential dykes whereas if you are on the outer slope you have this circle here which means that you have an out of plane sigma 3 so you are promoting the placement of radial dykes and this is pretty much consistent with what has been observed at least during the last eruptions 2005 and 2009 these are the imaged intrusions during these two eruptions this is a seal and this is a dyke this is an incline sheet which is then twisting along a radial axis to become a radial dyke towards the other part of the edifice so this is just to say how important is to consider the unloading especially on the caldera pattern of circumferential fissures here and the load of the volcano to explain the pattern of radial fissures outside so the idea is that caldera loading promotes sealier and the proximal concentric dykes whereas the load of the volcano promotes these radial dykes outside so we may try to go further and put Fernandina in a wider context actually reporting here the length of all the circumferential fissures against that of the radial fissures and here this pressure ratio where there is the unloading pressure and the dyke over pressure so for example Fernandina has a high unloading pressure because you have a deep and wide caldera and you have a small dyke over pressure because in this case you have some dense magma then you have basaltic magma and the magma chamber is very shallow so you need relatively low pressure to inject the magma to the surface on the opposite side of the diagram we have for example top of our campifragre where the topographic expression of the caldera is lower actually it's not so evident especially in campifragre and you have a deeper chamber and a lighter felsic magma so you have a different behavior here in this case so this is just to say that it may not be only the unloading which is somehow driving the presence of this circumferential dykes outside the caldera rim but it may also be important to consider the depth to the magma chamber as well as the composition for example here if we have lighter magma, felsic magma I would expect this lighter magma to go straight up without really turning and twisting to the side of the caldera now let's look at this campifragre which lies on the opposite side of the diagram and to do this I will show you what may have happened just before the last eruption at campifragre in 1538 because the problem when you deal for example with a caldera which has not been erupting for a long time is that you really don't know how the magma may be transferred there is no evidence maybe if you have an intrusion you know that the magma is there but you don't know how it may reach the surface so if you are able to reconstruct the last eruptive event which is the one which is near most to you you may try to say something and well campifragre has a limited topographic expression because the topographic difference between the uppermost part and the bottom part which is here in the sea is not very few actually so it's not like Fernandina and also but there is still some possible unloading which is also related to the difference in density between the deposits the sedimentary deposits within the caldera and those outside the caldera so you also have to take into account for the density difference and so it may have some unloading but it's much limited than Fernandina and the interesting point is that all the last and rest episodes I show you before they are culminating in this area in Potswoli so the maximum uplift is here and these these rest episodes have been interpreted to result from the pressurization of a magma chamber which has this shape here in map view this extent this green ellipse here which is an oblate reservoir and this has been consistently responsible for all these unrest episodes and the nice thing is that if you look at the resurgence because we have resurgence in Campi Fegré the resurgence is testified by this last start Samarin Terras so this was below sea level and then it has been uplifted now and the culmination of this terrace again is in Potswoli so this suggests that the longer term uplift coincides with the shorter term uplift resurgence has been occurring in the last well at least this resurgence has been occurring in the last 5000 years so we can say that in the last 5000 years the system the magmatic system was probably there and it has been controlling the shorter as well as the longer term uplift episodes and this is the limit of the uplifted area the yellow ellipse the limit of the uplifted area of the resurgence and this is Montenovo so that's where the eruption occurred in 1538 and there are some very recent geophysical and geological data which suggests that Montenovo was fed by a daik, north south trending daik which is actually circumferential with regard to this to the present magmatic reservoir so what we did is to exploit the unique amount of information we have on Campi Flegre because we have several historical buildings and monuments along the coastline these black points here which have been quite well monitored in the last 2000 years I would say because there is a wealth of historical, archeological information as well as of course geological paleontological and geodetic information so that it's possible to reconstruct the apparent sea level variations in correspondence of each of these benchmarks in the last 2000 years we have 20 benchmark along the coastline and actually it's not the sea which has been moving because the sea has been pretty much stable in the last 2000 years so we have to think about the ground movement so the coast was going up and down this is an example from Serapeo do you know Serapeo? Serapeo in market which was submerged until the early 60s and then after the latest uplift episodes today is about sea level and you can reconstruct from this and other monuments the ups and downs of the caldera in the last 2000 years and this is summarizing these diagrams I will not go into the details but the message, the summary is that just well a few centuries before the eruption so from 1251 to 1536 there was a strong uplift which was culminating again in the Puzzoli area 14 meters of uplift culminating here so this was very similar to what we have seen on the short and on the longer term but in the two years just before the eruption the uplift was shifted here in the area of the future mountain of event so the maximum uplift moved here and of course in this analysis we tried to remove any surface deformation which was related to the days immediately before the eruption which may have been induced by the emplacement of the dike so we did our best to do this and if we try to invert this deformation using these simple elastic models we end up with two sources one is just south of Puzzoli and within one error within some error I would say the longer term source and also the shorter term source which has been inferred to lie below Puzzoli this is at 4 kilometers of depth and then we have another source an eccentric source which is just below Montenovo at a similar depth this is the fit between the model and the data for the central source this is the fit for the eccentric source and this is the conceptual model behind what we see is that the magma has been accumulating within the central magmatic system for centuries just below the center of the caldera and then at the last minute two years before it has been laterally transferred to an eccentric reservoir and from here a dike a circumferential dike was propagated so we have this lateral transfer of magma which we may interpret to result in the loading of the caldera from the moderate unloading of the caldera which is induzing this stress distribution the one you saw before from a vertical sigma tree below the caldera to an inclined sigma tree to the side which is induzing the lateral propagation of magma and then the vertical propagation of dikes and the interesting thing is that it's not only this eruption which may have followed this behavior if we plot the location of all the vents in the last 5,000 years from the center of the caldera radially outward we see that these vents they peak at 3 kilometers from the center of the caldera so this shows that in the last 5,000 years despite the maximum uplift has been systematically occurring in the center of the caldera magma was transferred laterally outside, immediately outside the most uplifted area this is the limit of the resurgence so just outside the resurgence and within the caldera folds so this suggests that we had this mechanism we had during the mountain overruption may have been occurring also in the last 5,000 years so it may have been a more general mechanism which is due to unloading which is able to migrate the magma laterally eventually erupting outside this most uplifted area and it's not just campifragre because if you start to look in the literature also in this database of rest episodes in the last 25 years there are other rest episodes which share a similar behavior for example Rabaul there is Azo there is Okmok and also Toya so this may be a more general mechanism which is applied to many calderas so what we have seen is that the role of unloading in calderas in two different cases in one case where we have a large unloading we have a magma transfer outside the caldera rim in the other case where we have a smaller unloading we have a magma transfer within the caldera but still outside the central part of the caldera and this is interesting because it's also important for the assessment because if next time if you see a large a very large uplift in the center of a caldera I don't have to expect necessarily to have the eruption there the eruption may occur in a peripheral way in a peripheral area of course this is a very schematic approach I would say because we may have a lot of complications for example regional tetonics we have some extension or compression this will affect our stress trajectories so the height path will be affected as well and as I told you also the composition depth to December should also be taken into account so the final message about these lectures the first is the importance of the amount of subsidence for a fixed diameter of a caldera in controlling the structure and the evolution of a caldera second is the importance to understand the unrest processes which seem to depend on the composition and the opening of the system and the challenge is to try to understand in a physical way the observations we have from a statistical point of view and finally we have seen how unloading may play a different role in different types of calderas that's it, thank you very much


Hi, I'm Patti.  Being disabled is being trapped.  I I hate it and I'll never be okay with it In rehab, you are given a training leg basically a pipe and a hinge, but it was severely severely uncomfortable I got a quote for a definitive leg $60,000 which is basically the same leg that what our veterans would get the government does have a program It'll cover maybe $8,000 of the leg. I just I don't have insurance So I want to be able to be independent of that. I don't have to rely on government subsidies I don't want that. That's that was never my intention to sit on disability for the rest of my life I want to be able to say yes. I got a leg. Yes. I'm getting a job. Yes I'm out in the workforce and doing something with myself. I'm not sitting here feeling sorry for myself And at the end of the day, you can't you can't hold someone's hand when you don't have a leg I'm either in a wheelchair or I want crutches and there's no connection anymore I think that's one of the main reasons. I just want to walk because I have never held my children's hand when a school ever If anyone could benefit from that second leg, of course, it would be Patty She would only continue to do what she already does and that's given help others So it's all about coming coming back and she certainly would deserve it Patty is one of the most dynamic strong fiercely independent women that I know I can't imagine the levels that she'll hit when she has her full mobility. Nothing's gonna stop her She's just one of those people that make you feel happy It would completely transform Patty's life and give her the freedom that everybody else enjoys and takes for granted Having that leg will really make it so much easier for her as a mom You know things just taking the kids to the park for instance I want that for Patty and I think this will really help. Patty is someone who gives of herself Constantly it's time now that we give something back to Patty. She deserves this more than anyone I know mostly because she's just taken this all in stride and she's never asked for anything from anyone Be productive be useful be whole. That's all I want. I just I just want to walk


We're back with the breakfast and plus TV Africa. GD Johnson joins us this morning for Off The Press. GD, happy new year and thank you for joining us. Okay, I think we seem to have audio connection challenge right there. I hope we're able to sort that out as we progress. Now quickly, we start off with the punch newspaper this morning. Looking at the punch newspaper for the big stories, 28 governors pile up 5.8 trillion naira debts for incoming government. 28 governors pile up 5.8 trillion naira debts for incoming governors or government. State debts to increase above 200% of revenue in 2023. That's according to the World Bank. Lagos cannot execute laudable projects with loans. A commissioner is quoted to say, but the question would be if, I mean, there's a lot of revenue that's being generated in Lagos. What's Lagos business in getting loans? Consumers say electricity tariff hike illegal. Anger spreads. Federal government gives operators ultimatum to name oil well owners. And two senior lawyers want EFCC scrapped. Just before we move away, you have another one saying, Macking Day Kickstart's second term campaign faces multiple battles. And commuters grown as Jilos Berger returns. That's the Lagos Ibadon highway. How Lagos police man ministry paid 185,000 naira for new bond. These are very hard times, sad times, very inhuman, if you ask me. The nation newspaper says presidential poll G5 keeps PDP supporters in suspense. G5 keeps PDP supporters in suspense. I have never seen it, you know, such a dramatic election year. Macking Day to announce preferred candidates, governors protest exclusion of articles name on list. NFIU to enforce ban on cash withdrawal from public accounts match the first. All APC governors behind Tunubu Suleiman affirms and Council autonomy are headache on constitutional amendment and 22 fuel stations sealed for selling above approved price. Reg Bachelors men in Oshun APC campaigns team is quoted to say these are the headlines you find. But we just turn our attention to the Guardian newspaper this morning. The Guardian says the 2023 term inflation in security fuel subsidy expert tells government term inflation in security fuel subsidy expert tells government and it feels like we're able to control of this. Then just maybe, you know, economists just going ahead. One and wrong steps ahead of elections. It's significant a year for Nigerians. How electorate outcome will determine economic progress, inflation, cost of living crisis among major challenges. Now truth is the 2023 election just as every other election, but I think this is very critical. It's going to be, it's very significant because investors individuals, a lot of persons are waiting for the outcome of this election and the outcome of the elections will determine whether would have more investment or investors will pull out of the country and what have you and how many persons would you know relocate. The word would be jackpot. But that's that's a lot to consider. Most importantly is that every other person gets their PVC.  AFZ shouldn't be in existence. Nigerian constitution falls 40 says. Now federal government to transfer 613 rehabilitated repentant terrorists to states. Federal government to transfer 613 rehabilitated repentant terrorists to states. Those against obese endorsement by President Olusia Gunobasanjo. Don't mean well for Nigeria. Ohaneze is quoted to say how cost of production import dependents undermine national drug security. I said this morning on the Guardian newspaper and quickly we have the daily trust cash withdrawal from government account and match the first. NFF IU is quoted to say officials to receive extra code allowance through accounts. Federal government states local government we drew over 1 trillion since 2015. Implementation requires political will exporter saying and that's also out of not out of the conversation. Program ought to have started alongside TSA. OPEC all output increases as Nigeria rebounds. Bauti Emea replaces Belukarefi with Ahmed Kari as new Wazzari and 18 Boronu passengers burnt to death in Bauti auto crash. Ina divorced PVC collection towards and registration areas. We spoke yesterday with the HOD of publicity right here in Lagos and she had mentioned that. Five days old Boyerics amputation over doctors negligence in Kano. Local government autonomy bill hindering constitutional amendment that's what Omoa Gege is saying and APC governors not in a secret deal with the TIKO national governor's quoted to say. Let's quickly bring a guest in share his thoughts on some of the headlines this morning. GD Johnson it's good to have you join us. Thank you so much. Well we hope that we have GD Johnson you know connected to us as soon as we can but the headlines this morning if you go through the pages from the punch to the nation the guardian and the daily trust newspaper the headlines the headlines are beg your pardon very interesting. I wonder it's a standing it's the fact that you have lawyers asking that the EFCC be scrapped and that that's a very strong one and you also have the fact that when we talk about revenue because we seem to be dealing with the revenue issue in our country as a people 28 governors pile up 5.8 trillion a debt for incoming government or governors however you want to put it but 28 don't forget that we have 36 states of the federation including the FCT so look at the ratio look at the calculation that's a lot but what exactly is going on and we have constantly accent queried you know the pattern where we have to be highly dependent on the center for allocation it's a very healthy and if it's not healthy then how come we have not been able to decentralize and ensure that there's resource control that conversation that word resource control has been in a lexicon for a very long time and everyone says we need to you know states need to be able to control their resources people need to be able to you know get to a point where they say the resources that we have were able to you know utilize them and then make do with it of course remit to the center not the other way around but are we really sincere with this conversation and has this pattern not made us very lazy can we be progressive if we get to a point where we're able states are able to control their resources the argument against that has been that just with how you know governors have acted it's also possible that this governor's you know will be too powerful you know towards our resources and there's a lot of argument because if you talk about state controlling state resources you also talk about state police gd johnson has reconnected with us gd it's good to have you join us and thank you so much for being part of the show all the analogies with respect to resource control i mean we've been very fond in the room that nobody's interested in talking about and then if you look at the amount of money what we're talking about resource control we're talking about restructuring and then unconstitutional review is about distribution of power across the various tiers of government it is exactly the judiciary and the legislature and then across the various various tiers of government with local states in figure and then various organs of government legislature judiciary and the executive however we are not having that conversation and we have spent a lot of money trying to review the constitution i think we have spent over 12.8 trillion over the years reviewing the constitution are not active in it now we talk about resource control one of the things about it is our local government autonomy which was in the middle element of the the constitutional review of the niger assembly and which was also part of the executive order 10 that was challenged in the court and the country not most of the state is not most of the state has to be assembly unfortunately if we get this state like it goes to it is not even interested in local government autonomy because there's no sense in so we are not having that conversation and it's like we are in the same cycle we are not making any progress because if we don't have resource control you can't have you can't have constitutional federalism without having fiscal federalism you can't practice federalism and practice federalism on paper and then don't practice fiscal federalism with each for each unit of the nation as we control over the resources so if that's what we have found ourselves and with respect to that we continue to talk about it because we have a major constitutional review that allows your state to retain part of whatever revenue that comes from the state and local government as well so that's that's the situation we keep talking about the other thing I'm interested in is the big price so no one is talking about restructuring they're about giving back to the community and the rest of it but how long will we continue you know in this type of practice right and I mean look at that psalm that governors have actually 28 of them have left that amount of money that's on the punch newspaper you know for the incoming government or governors isn't it really worrisome should we we get to a point where states should be allowed to express because for instance there are several states for when we look at states they are naturally endowed with different resources the amino resources that we're probably not paying attention to what why shouldn't we allow states to be creative explore what they have and then you know get revenue rather than being dependent on the kind of system that we operate where they have to go to the center and now we know that the center is being threatened because of our inability to you know keep up with all proceeds which is also a major factor that contributes to our revenue so easy you're worried about the state government you're not worried about the federal government as well and it's we're not going with as you saw us as the final check to give you the approval it's a bit boring I don't know whether it's 77 billion or 77 billion dollars that it should not go mad as to being out there for 77 trillion nair 77 billion 77 77 trillion 77 trillion thank you very much 77 trillion nair that's a federal government is leaving the national assembly that should serve as a tech is near is almost a robust term I recall there was an issue where the president bought a request to to seek for a loan and even the speaker of the house of rep and the senate president did not even allow for a debate when members are calling for a debate the real thing out of assembly are an extension of the office of the governors of the taxistic state and governors that we have in Nigeria so the real institutional checks that we have in place are not doing their due diligence they are allowing people to to do whatever they want to do without the cost of due process loans and procedure you have to say what do we have to shoot for all of this money that we have borrowed and then some of them still have the gunshot to go about campaigning for for their success and some of them still have your density to see campaign under the platform of the party that has been in government for close to eight years and then you have nothing to shoot for it you know if you have debt incurred by government and you have something to shoot for it you're interested in paying for it there's no doubt that government across the world has the most debtors however you will borrow debt to do infrastructure to build your site to build the economy not to fund their lifestyle in Nigeria we are we are borrowing money to fund the lifestyle of of our elected officials and public office and i have said it don't take a key and take a trip to the to the to the various and secretarial state government secretariat or local government secretariat or federal government secretariat or where you have locations of the ministries and departments and agents of government across the seven of the six local government across the 36th government federal capital and the federal government and you'll be shocked at the type of car we drive as official car is only in Nigeria that i see people are using luxury cars and non-functional cars as as as official car and then we complain that we don't have money we complain that there is inflation we complain that people need to pay more taxes yet government that is not engaging in bell typing how do you justify the use of travel and an official car how are the various of the various types of cars that that that that the drive that we borrow money not to build infrastructure we borrow money to fund the lifestyle of our public and elected officials so we have nothing to show for it Gide Johnson i mean you're actually not far from it is a reality because if you look at the 2023 budget as much as that budget is not one that we are we have the capacity to fund we don't have what it takes to fund the budget so it means we're going to borrow but in the content of the budget if you look at it some of the you know content of that budget is not for the national interest but for personal interest especially with the house you know the national assembly increasing allocation from 59 billion to 288 or there about a billionaire but let's move away from that conversation would always have that and we'll continue to talk about these issues until we get to a point where it sticks and that would mean that we have taken the right action and taken the right decision now two senior lawyers want EFCC scrapped abacuba is part of them and he's made several argument that's on the the uh patch newspaper this morning now according to him he said that the economic and financial crimes commission should not have been in existence he stressed that the commission currently operates outside of the constitution however the reference is that it does not have the power to interfere with the activities of state government and so because it's a creation you know of the federal government they can't interfere the argument is almost you know it's lengthy there are too many issues that he's raised but i'd like to share your thoughts on that what do you think should EFCC be scrapped well i mean between i mean between in the sense that and the EFCC mandate for me has focused on prosecution other than prevention why do they wait for these crimes despite we having these agencies we have seen that most state government most agencies of government at both state federal and local government level are not complying with financial regulations with respect to their words of contract and the rest of it what are the systems that you are putting please to forestall that they are all what we see the EFCC coming out to tell us that this presents to 20 billion 10 billion the question we ask is when did they start how did they get there what were these agencies and what are they doing were they not tracking the accounts of these individuals were they not tracking the accounts of the federal government so beyond arrest and prosecution what steps are they taking to forestall that that for me is an area where i question the existence of EFCC because it's economic and financial crime so in what way are they are they to ensure that these people don't damage the economy before it becomes the financial crime now someone is an account general of the federation it's meant to ensure that the allocations and money put in for are distributed and sent to various different agencies of government you have the general of the federation so these are these these these are 50 cards that you put in place out for EFCC to work with this with these visual services and you have the people able to ensure that there is intelligence and compliance with financial revisions other than coming out and arresting people at the end of their tenure parading them and engaging in these attire so means here's the engagement in human shift and doing the actual work so if you look at it from that perspective yes i think there's a link for us to scrap EFCC because at the end of the day um how many how many cases have been successfully constituted particularly with respect to financial crime at the state federal and local government and local government level compared to cases that are prosecuted for people engaging in in other if we're us activity advances from and the rest and the rest of the world and then if you also look at it was the federal government established when it has not been domesticated across the state so if you look at it from that perspective there can be an argument from some lawyer that they cannot use an agency of that government it can only apply in the future any proof we do have a system of government and like it can only apply at that level okay but um what about some of the consents that he has raised the fact that the EFCC is a creation of the national assembly and it doesn't have the power to interfere with the activities of the state government so i think you have that you know so it means you know some things i think um can stay i think i'm adjusted or some other things you know they have their own EFCC and by by statues of federal government all of this is meant to have domesticated this agency for it to be for it to to to agree but you know when it was established we asked he should bring three leaders as head of state to some things who are railroad and those are the for me 15 of other if you are if you are talented then probably you wouldn't have wanted gone this in the end the needs to have domesticated each of the state has to ascend the needs to have to have ascended to to to that to that that that that established EFCC at the federal level for it to operate at the state level so i agree with you that with that argument yes not that about that but you know there are a lot of things that we do in this country that are not followed with due process and then we just allow you to fly over time the garden newspaper says uh expat are asking the government to tame inflation in security and feel subsidy uh according to this expat this problem i just chart the cost for 2023 uh do you really agree with this uh expat yeah we need to be with inflation we need to be in security on the EU of foreign subsidy is not going to be the position of your hand because you look at the afternoon players that at the federal level to be worth price of position they said the government was not doing anything on subsidy and they came on board in that sense we need to the major factor that had to populate their party to popularize their movement was the was the was the first of subsidy a protest of 2012 and which but the the problem for general administration then so if you look at if you show no that about that you have the immediate impression in security about that it is practically impossible for people to travel freely across the length and breadth of this mission on the subsidy i don't know whether we are paying subsidy or we are not paying subsidy the the fact in the end is that we are not buying the foil at the same price at different price stations some are telling me 325 some are telling me 350 some are saying 170 so we don't need government's opinion on opening because we don't have a true picture here no transparency when it comes to the major foreign exchange for this mission which is the oil and gas sector the oil and gas sector is under the office of the president because the president himself is also the minister of the kingdom he doesn't have any minister of steel so for me i don't know what the experts are saying with respect to the experts in that area they can see but we need to deal with inflation there's no doubt about that we need to deal with insecurity and these are the kind of questions we need to ask people that have come in into the presidency i asked i am following the campaign clear since it is only presidential candidate we just go and spend 60 seconds 60 to 90 seconds ask them to clean the music that they want to dance and turn them and tell them go for me i will i will solve your problem without antiquity without thinking what will be the policy it was and people will shout and then they will scream and then that is that the end of it it across the party across the party with a session of one party across the party what you see they are coming in to go together to go together clean music for them entertain them make them to forget about their problem and lose their sense of wisdom for some time rise on their emotions and then at the end of the day this past and then they begin to share the the the vision of of of their campaign talking about the mama's crowd jenia johnson you know how these things are done it's not done you know if you have if you have never been involved in politics you understand you mobilize from the local government you use these resources to do that and the local government here who you have them is official each of the local government let me see very quick kind of for example you have for the foreign government each of the local government you have them to come with one thousand people they mobilize this one thousand people they give them and some some some amount of money the red boss jenia johnson you have for the four thousand already in the in the stadium so you these are the things that don't jenia just before we close this conversation down we're out of time this will just be the last quickly i'd like to get your reaction on this ban by the nigerian financial intelligence unit saying that it's limiting or it's banning the withdrawal from the federal government state and local government account from match you know the first 2023 you have that body you have that body what i've done what he's been doing before match the question i asked is and then the question i've asked from the intention of this administration when you are going about saying that the new government is fighting corruption and i said okay the only fighting corruption on the basis of news report i have not seen constructive steps it is a systemic effort for you to fight corruption what are the steps that we are putting in place what are the measures now um that nothing has changed in terms of in terms of process and procedure as that our people um disboss and access access and disboss public funds that you might be sure that at the end of this administration corruption in this administration we're much more than what people are talking about on the internet and i'm sorry to have been proven right over time because there are the safety guards that you are putting in place to post up an individual keeping his hand into the cooking gap the question you ask is what are they doing what have they been doing to prevent people from keeping their hand into the national force into the state force or to the local government force so you have these bodies that are existing on paper that are paper tiger that are not doing what they are supposed to do and that's why we have found out that we did that right so why are they with this much much much less 2022 to do what they have been assigned to do okay well uh let's see how all of that pans out orders have said that this is just another backing dog uh without the capacity to implement it and so uh you have raised valid questions uh gd johnson but we have to let it go at this point uh because we need to move on thank you so much for being part of the uh show this morning after press we look forward to sharing more of your thoughts and more critical issues of national interest thank you messy once again i've been here to have you as a member of the world and i've been here to you and kofi okay all right then gd johnson has joined us this morning but we we have to leave it at that and off the press would return on monday and of course the headlines would always be interesting because it's an election year we take a break when we return we'll have some more conversations please the brass


Hello everyone. So I have we're going to get started with the implementation of your linked list. I am working here with the code for your next assignment. So I have downloaded the code. I have unzipped it into a directory and I'm going to work in here for a little bit. So I encourage you to do the same. We're going to write some code together and some pseudo code. All right. So I am in the linked list.py class and you will see that there are a couple of other files in here for what those are. Just read the details of the assignment. For now I'm going to work in this linked list.py class. Okay. Now from the previous slides we know that there are going to be two classes involved with implementing a linked list. The first is our node that represents one node in the list. And do not change this class. It is written for you. It's got a constructor here and the constructor takes two optional parameters to default parameters. If you remember go check out the short video on default parameters. The constructor can take data which is going to be the item that lives at the node. And the next variable which is the thing that comes next in the chain. And if you don't give it anything when you call it these both default to none. And that's what we want. But be aware of that. If you do not specify values for data and next they will default to none. I also give you string methods and wrapper methods for printing these things out. All right. Now onto the meat of this assignment. Again you do not change the node class. But you are going to use it inside the linked list class which you are responsible for implementing. Okay. So the linked list has a class constructor. Don't modify it. Do not change this method in any way. But here are the variables you will be working with. There is the head variable. It is initialized to none when the list is initially constructed because it's an empty list. There's nothing in it. The head variable must always point to the first item in the list. So when we go to add and append things you're going to write methods called add and append. We're going to have to work with this variable. The tail variable must always point to the last item in the list. Okay. So again we're adding and removing things from the list. You may have to update this variable. And then we have a size variable. We're going to use this. We're going to keep track of the number of nodes in the list as we're adding and removing things. So this is just going to be an integer but we are going to have to update it. Okay. I also provide you with this method which is called ITER. Okay. Don't touch this method. What it allows you to do is loop over the list. Okay. It's special code. Again, please don't look at this code. Don't modify it. Don't try and adapt it. If you have questions about it, absolutely ask. But don't look at this code as a blueprint for doing anything. Okay. What it just lets you do is it lets you loop over a linked list that you have created. Okay. And that may be useful to you as you go to work on this assignment and try and debug things. Okay. But don't modify this method. I have to find the lend method here. So the lend method is one of those magical dunder methods. We worked with it in the last assignment. It supports calls like this. The length of the list, it returns you the number of items in the list. That's all. Okay. So all this stuff you don't deal with. Now, let's talk about putting data in the list. Let me scroll just a little bit so my head isn't in the way of the code. Okay. So we're making a list. One of the things we need to do with a list is add items to it. Now, regular Python's list with the brackets does not have a notion of add. Add is an alias for insert at index zero. Okay. Put something at the front of the list at the very beginning of the list. Okay. When you call add, so I give you extraordinarily specific instructions on what the behavior I expect out of each of these list methods. Okay. You must have this behavior to get full credit for the salient points in the assignment. Okay. So add an item to the beginning or the head of the list. This method does not return anything. And this method must have a big O of 1 implementation. Okay. So big O of 1 means this thing needs to run quick and constant time, regardless of the number of elements in the list. Okay. Add takes one parameter, which is the data item that we want to add to the beginning of the list. Okay. So I raise this not implemented error. This is just for me and for you for testing. So one thing I'll mention right here, you can run this code and it will automatically test itself. If you scroll, see there's these test add things and it says failed. Add is not implemented. Aborting tests. Down at the very bottom of this file is some code, some test code that runs a lot of different stuff. So you can run your code and it will kind of tell you, hey, did you get it right? Did you get it wrong? At least from an input and an output perspective. Okay. So if you start seeing past tests down here, you know, you're in good shape. If you start seeing failed tests down here, you know, you've got something to fix and hopefully the test will give you a clue about that. Okay. So all right. Let's start implementing. Step one of like our programming mantra is you've got to think about how you want to approach the problem. Okay. Well, let's think about this in terms of the special cases that it might run into. Okay. That's usually a good starting place. So let me switch over to my whiteboard for just a second. Okay. So I'm writing in red now because my black marker died. We're talking about the add method. Okay. So when we start out by calling the constructor with a linked list, sorry, I should be at this camera now. When I'm talking about, I instantiate empty linked lists. So there's nothing there at the beginning. Head and the tail of the list are both going to be none, right? When this first line executes. Now I'm going to add Alice. Okay. So what impact should that have? Well, conceptually, if I do it on an empty list, right? If I do it on an empty list, Alice will be the only thing in the list. And both the head and the tail of the list need to refer to Alice, right? And then the other thing I have to have a length of one. Okay. So this is kind of a special scenario, right? Something I need to think about. Adding to an empty list. Okay. What if the list is not empty, right? What would that look like, right? Adding to non-empty list. Okay. Well, if the list is not empty when I add to it, like let's, let's add Bob here. If I add Bob, what happens? Well, if I add Bob, Bob, he becomes the head of the list, right? Bob is going to now be the head of the list. Is now Bob, right? But Alice stays there as well. So we've got to tell Bob, now that you're the head, you've got to point, you've got to refer to the next person. So Bob's next needs to refer to Alice's node. And nobody comes after Alice. Alice has no next. She is the tail. And then we will also have to update the length. Okay. So what we do is going to be just both so slightly different depending on whether this list is empty or not empty. Okay. All right. So let's do the code here. Get back over to my code view. All right. So let's think about it. If, give me just one second here, apologize. If, okay. First thing we need to do is we're going to put some data in our list. So I need to create a new node to hold that data. Okay. So I have my constructor class or my node class. So I'll say node gets, right? I got a new node here. And the node takes two parameters, the data value that I want to put in there. Well, that is going to be item. Okay. Again, we're looking, we're calling this guy up here, the nodes class constructor. And it takes two things, data and the next node. Okay. So actually, let's be explicit about this first. Here, I've got an empty node, nothing in it. What should this node's data be? Well, the node's data should be the item. Okay. And what should the nodes next be? Okay. Well, in the case where it's empty, I can't see where I'm pointing. And there's only one node in the list. That node's next value is none, right? Because there's one item. Okay. That's it. Okay. So I've created my node. I've got a link in the fence. Now what I need to do is I need to put that node into my list. Okay. Where does it go in my list? Well, the head and the tail both need to refer to, right? But let's start at the head, right? The head, we're adding items at the head of the list. Okay. So self.head gets my new node. Okay. See what we did? We inserted it at the head, right? The head now refers to this new node that we created. Okay. Now, but we need to think a little bit, right? What would happen though, if somebody is already in the list? If somebody is already in the list, they kind of get bumped down, right? They get bumped down the list. What happened on our board? Well, we inserted Bob down here. We had to tell Bob's next point to Alice, right? Because Bob is now the head of the list. So we have to tell Bob, hey, point to Alice. Well, where was Alice before we inserted this, right? When Alice was the only person in the list, she was the head, right? So Alice is the old head of the list. Hmm. So, actually, this new node we're making, this is the Bob node, right, from earlier. The item value is Bob. But next needs to point to Alice. Well, where was Alice? She was the old head of the list, so we need to modify this. Okay. Alice is the old head of the list. Alice was the old head of the list. Okay. So this is really important. Self.head contains a reference to a whole node. And previously, that node was the node containing Alice. Now we're saying we've made this new node that holds Bob. And Bob's nodes next needs to point to Alice. Okay. So take a minute. Pause here. Make sure you really, really, really, really understand what these four lines of code does in relation to the example on the board and in relation to what conceptually is happening. Feel it. Make sure you understand each and every line. It's so critical that you do. Okay. So again, pause here. Take a minute. This is big concept stuff. Make sure you understand what self.head is. Play with it. Look again at the example on the board. Understand that whether this is an empty list, whether this is a list with one item, whether this is a list with 10 million items, this code works. Okay. Take the time to really grasp it. Write out some examples on paper. Okay. All right. Now, this code is fine. I'm going to shrink it down in a minute. We haven't taken care of all the housekeeping we need to do. Remember that there is a tail here. Right. Now, if there's already data in the list, if it's already got a node in it and we're adding to the head of the list, we don't need to worry about the tail. The tail is always the tail. And unless we delete something, the tail is just going to keep, you know, moving on out. Okay. But in that special case where the list is empty, where there's nothing in there, we need to set the tail to be the only node that is inside. Right. In the case where we only have Alice in there, where we're adding one node, the first node, we also need to remember to set the tail. It's the only time we need to do it. Okay. So we can, we have a variety of ways of figuring out if the list is empty. One very simple way is to ask the list, hey, is your size zero? Are you empty? If so, then I need to set the tail equal to the new node as well. Okay. Right. When I insert into an empty list, when size is zero, both the head and the tail must point to the same thing. But as I add things, as I insert them at the head when there's already an item, I don't need to mess with the tail. The tail kind of, the tail's tail, as the thing grows, the tail stays the same. Okay. All right. So I'm going to take advantage of my constructor here and shorten this up. Okay. So remember, the constructor can take two parameters, the first being the data. So node is item and node gets self.head. Right. I'm just making, taking advantage of the constructor parameters here. It has the exact same effect as these lines of code right here. Okay. So go check out the constructor. Right. I'm just doing this stuff in one line. Okay. So I can get rid of these lines. Okay. Now there's one more thing I have to do, one more little housekeeping thing, which is what? I need to update the size. Okay. All right. I'm ready to test this thing now. When I go to test, you need to remove this line, this raising and not implemented error, just from the method you wrote. Okay. So we completed the add method here. Let's run it. Okay. Right. So my testing add. So this kind of tells you what it's doing, how it's testing it, add calling add Alice to the list. And this little arrow here is the return value. Now adding does not return something. Okay. It just changes it kind of like when you append to a list just changes it, doesn't return anything, just changes the list. But after I add Alice, the head points to Alice's node. That's good. The tail points to Alice's node. That's good. The length of the list is one. That's good. Then I add Joe. Remember adding inserts at the beginning of the list. So now the head is pointing to Joe. That's good. And the tail is pointing to Alice. That's good. And so on and so forth. So kind of like what would be a really good exercise for you would be to conceptually follow these steps, you know, where it adds in here. You do that conceptually on paper and convince yourself that the head and the tail are remaining updated. Okay. Remember the linked list, it only has three variables it knows about. The head, the tail and the sides. So you got to keep those current and up to date. All right. So take some time to wrap your head around this. Make sure you understand it. And we'll see you in the next video where we're going to talk about appending.


Hey guys, it's Monica. I thought I would do this tag while I was still up here in Barhabar, Maine on vacation And I'm gonna have Jay actually read the questions off camera But this is Michelle cinnamon girls beauties tag called the Sun Kissed Summer Tag And there are 15 questions that Michelle came up with and again Jay is going to read them off camera And I think this is a really fun tag What are your go-to products for a Sun Kissed Summer Glow? Okay, so you know I have a new summer favorite and that was the dermatology I was actually sent their SPF sunblock and also their 50 SPA not 50 SPF their SPF Moisturizer and I will tell you I love that moisturizer. It gives me a lovely tint. It gives me a lovely glow I absolutely love it other than that. I've been using the billion dollar babe contour and I think it's a highlighter. It's a stick and I'm enjoying that tremendously as well question number two, honey Yeah, what book would you recommend for a summer read? Oh my gosh It has to be Outlander hands down now. I read Outlander many many years ago. Love the Outlander books They are fantastic. There's a number of them. She's coming out with book number nine I think this year well probably next year now But the TV series the audio books, it's fabulous. So if you've never read the Outlander start with book one and Be prepared for an escape. It's a romance. It's all about family value. It's all about culture. It's historical. I Absolutely love Jamie Fraser And my husband. Yeah, I love Outlander. I think it's a it's a great series on Stars and I'm sure the book is like you say is ten times better. So yeah, absolutely I highly recommend it to and it's on Netflix as well That we can see it, but there's a seal float note. I don't know if you can pick it up on the camera I can't see anything in the camera. Oh, it's too bad question number three. Okay question number three What is your signature summer scent? Oh, I'm so boring. I really don't have a signature scent I switch my perfumes around all the time But I would tell you that my favorite scent at all of all times in the summer is that smell of the salt water at the beach The ocean it's just that salt smell in the air. I love it Number four the sun is shining and it's time to get outside. What is your favorite outdoor summer activity? If it isn't walking the beach, it is camping. We camp as often as we can. We're here in Bar Harbor main camping This is our annual camping vacation. We do 10 days up here every summer and we never tire of it. It is a gorgeous Number five you're at the beach boardwalk and your stomach is grumbling What is your favorite beach food or snacks? Well favorite beach food would definitely be Lobsters and steamers if I can get it or if I'm at the boardwalk Sometimes fried clams. You can just order a small order of fried clams. That is also fabulous Snacks, I would have to say an ice cream cone All right number six sunscreen is always important, but it is a must during the summer What are your go-to products? I would have to say it's the Australian gold. I've been using that For I don't know three years now. It always is dependable. It always plays nice with my makeup I can reapply it if I need it. It's affordable. I never run out of it So far that has been my go-to now this summer I've been exploring with a couple of others like dermatology But Australian gold is still my go-to Okay, number seven after a day in the summer sun and the heat. What do you do to cool off?  But just like what you see it lately. I usually have it up in a twist with a bun Or just a twist in a clip and or sometimes I just have it down with hat on or a visor on I'm very casual in the summer unless I'm wearing a wig Number nine must have nail polish for the summer. I am so totally boring It's clear. It would be clear nail polish all the way ever since COVID hit and we couldn't get to the nails a lot I just pulled off my gel nails. I have not put any fake nails on since I'm letting them get healthy And so it's just a gel polish Number ten sometimes it feels good to just chill out and watch Netflix which shows or movies? Do you recommend? Oh You know, I don't have Netflix But the types of shows if I'm going to watch them. I'm a real I'm a major true crime addict So I like watching your true crime dramas. I love watching historical dramas and of course outlander Yeah, if you have stars and I know if you have Netflix, they've got a couple of seasons on there as well So that's my escape Number 11, do you wear liquid foundation? BB CC cream or tinted moisturizer during the summer? Basically tinted moisturizer as much as possible the dermatology. It's tinted moisturizer is awesome But never fails in the summertime, especially I get a good foundation and it doesn't matter if it's a BB cream It's light, but I get a good foundation with a 50 SPF in it and right now. It's the boots number seven Protect and perfect that has the 50 SPF. That's awesome Number 12, it's so bright outside. Do you wear sunglasses or a hat? Oh, yeah, both Well, right now I have both on because it is so bright outside and I wear sunglasses every day Basically all year long winter summer fall. It doesn't much matter I really think that wearing sunglasses helps you with your eye wrinkles, especially good sunglasses I don't always really wear super good sunglasses, but I Have a lot of sunglasses and I and I try to wear a hat when I'm outside as much as possible My hairdresser yells at me when I don't because the sun bleaches me right out 13 what is your summer jam this year? Well, my summer jam is the same as all the years. It's camping. I just love Going camping love coming up here to Bahá'a or going to booth by harbour or camping at the beach That's my summer jam. That's what I look forward to doing in the summertime beaching camping and that stuff 14 bikini can't key or one piece Definitely a one-piece or an oversized t-shirt. That's more me. I am not bikini body And that leads to number 15 summer wouldn't be complete without a scoop or two of ice cream What's your favorite flavor? What do you think my favorite flavor is? I'd have to say you are so boring. It's got to be coffee. It's coffee Yeah, coffee ice cream is my favorite flavor I think my second favorite flavor would be a vanilla fudge type ice cream, but coffee is my go-to ice cream I love coffee ice cream a lot. So does that complete the tag, honey? That completes the tag. Thank you You did great. Thank you for being a good sport and meeting the questions to me You're welcome. So thank you guys for all watching and if any of you want to do this tag any content creators Please do it. I'm sure Michelle will absolutely love it again. This was Michelle cinnamon girls beauty tag I will link all her information below and I think it's just a fun summer tag So thanks for watching guys appreciate every single one of you. Happy summer


I'm Andrea Vell, Executive Director of the Advisory Committee on Reactor Safeguard. In 1957, an amendment to the Atomic Energy Act of 1954 established the ACRS as a statutory committee reporting to the NRC. The committee has four primary purposes. One, to review and report on safety studies and reactor facility license and license renewal applications. Two, to advise the commission on the hazards of proposed and existing production and utilization facilities and the adequacy of proposed safety standards. Three, to initiate reviews of specific generic matters or nuclear facility safety related items. And four, to provide advice in the areas of health physics and radiation protection. The ACRS can consist of up to 15 individuals who are technical experts. The membership currently includes expertise in the following fields. Nuclear engineering, risk assessment, chemistry, facility operations management, severe accident phenomena, material science and metallurgy, digital instrumentation and control systems, thermohydraulic and heat transfer, mechanical, civil and electrical engineering. The ACRS meets as a full committee approximately 10 times a year. They deliberate as a collective body and provide advice to the commission accordingly in the form of letters, reports, white papers and memorandums. Each meeting is led by the ACRS chairman with the meeting agenda being organized by each technical topic needing to be addressed. NRC offices and other interested parties may be invited to present. The lead engineer on the ACRS staff is the liaison between the committee and the NRC office responsible for the agenda item. Based on the recommendations of the subcommittee and the recommendations of the full committee meetings, the ACRS collectively writes letters and reports to the commission providing their recommendations and conclusions regarding a specific topic. The basis for the Federal Advisory Committee Act is to increase openness and transparency and government operations. Since 1972, the ACRS has come under the auspices of the Federal Advisory Committee Act. Therefore, their deliberations are conducted primarily in public and their reports and memorandums are open and available to the public.