Tobler, Steno and Geologic Maps






Map of Yosemite National Park.svg


Not at all.






Yosemite USA.JPG




Can you figure out the temporal relationships in this cross section?




200 Years of Geological Mapping













Edited some typos (12/7/15)


Using Beetles to Learn About Past Climates

How many species are there on Earth? Nobody really knows, but one study estimated the number to be about 8.7 million and most of these species are insects.

The largest group of insects are the beetles. Beetles make up about 40% of insects and 30% of animal life. Why are there so many beetles?

Scientists used to believe that beetles had high rates of speciation, but a recent study co-authored by the awesome Dena Smith suggests that beetles might just be really good at avoiding extinction. You can read the paper here.

This resistance to extinction means that many beetle species are very old. Species living now were around millions or even tens of millions of years ago.

Beetle species don’t just live a long time, they are also fussy about where they live. They want the humidity and temperature in their homes to be just right. If it gets too hot or too wet or too cold, they move out and find another home.

Long species durations and specific habitat requirements make fossil beetles very useful for learning about past climates, especially the Pleistocene.

The Pleistocene Epoch is defined as the time period from about 2.6 million years ago to about 11,700 years ago. Like today, the Pleistocene was a period of rapid climate change. During this time there were between 20 and 30 glacial intervals where much of the world’s temperate zones were covered in ice. These glacial intervals were separated by warmer interglacial periods when the ice receded. This map shows the Wisconsinan glaciation 18,000 years ago.Glaciation

I wanted to see if I could use GIS techniques to reconstruct Pleistocene climate using fossil beetles.  I chose two sites for my study: The Titusville Peat in Pennsylvania and Ziegler Reservoir near Snowmass, Colorado. The Titusville site is an ancient peat bog during the mid-Wisconsinan interstadial between 43.5 and 39 thousand years ago (Elias, 1999).

Ziegler Reservoir is located near Snowmass Village, a ski resort in Colorado. In 2010, work began to widen the reservoir, but the remains of a mammoth were uncovered, leading to a paleontological excavation. Numerous mastodons, mammoths, ground sloths, bison and camels as well as insects were recovered from the site. Carbon dating indicates the age of the site ranges from 126 to 77 thousand years old (Elias, 2014).Sites

I obtained the list of species for Titusville from the Paleobiology database and the species from Snowmass from Elias’s 2014 paper about the site.

I looked up species ranges using Global Biodiversity Information Facility (GBIF) and USGS’s Biodiversity Information Serving Our Nation (BISON) databases. These are sites that list museum specimens. Each record includes the longitude and latitude where the specimen was collected.

To determine climate preferences, I used two sources: The global ecological land unit map and Koppen Geiger climate zones

The global ecological land unit map was developed by esri and the USGS. It is a 250 m resolution raster containing information about bioclimate, landcover, lithology, and landforms. Here are my fossil insect species on top of the global ELU map.GlobalEco

The Koppen-Geiger climate classification was first developed in 1884. It has been revised several times, but remains the most widely used climate classification system. The system divides Earth climates into 30 zones with unique temperature, moisture and weather properties.


I used GIS a sequence of spatial joins to connect the ecological and climate data to species. I learned that 43.5- 39,000 years ago, when the Titusville Peat was deposited, Titusville was in Köppen Geiger zone Dfc, which subarctic with cool summer, wet all year. This means that winter temperatures were as low as -40 C (-40F) and summer temperatures as high as 30 C (86F) — much cooler than current climate zone Dfb (humid continental). The bioclimate was cold and wet and the dominant vegetation included needle leaf /evergreen forests.

The Snowmass data was more complicated because it represents almost 50,000 years and the site is on a mountain. On mountains, wind picks up flying insects from warmer, lower elevations and carries them to cooler, higher elevations in a process called orographic lifting.

To compensate for the long time period and the effects of orographic lifting, I divided the beetle assemblage into five time intervals and I removed all the flying beetles from the analysis.

The climate at the Snowmass site was initially similar to today’s climate. Insects suggest Koppen-Geiger Zone Dfc, subarctic with a cool summer.Over the next 2-3 intervals, the climate gradually cooled from Zone Dfc to to zone ET (tundra with no warm season). By the 4th interval, all insects indicated Koppen Geiger zone ET or tundra. But, in the last interval, the prevalence of insects from Zone Dfc indicates warming. As in Titusville, the bioclimate was cold and wet and the dominant vegetation included needle leaf /evergreen forests.

You can see the modern distribution of Dfc and ET in this map.SubArcticTundra

Using insects to model past ecosystems isn’t a new idea. But, as far as I know, no one else has used GIS to join insects to specific ecological variables for climate reconstruction. I will be presenting the more scientific version of this research at the Geological Society of America Annual Meeting in Baltimore on Tuesday, November 3.

On Shaky Ground 2: How Earthquakes Teach Us About Geology

My first earthquake was the Loma Prieta earthquake on October 17, 1989. The 6.9 magnitude earthquake is also known as the World Series Quake because  millions saw the earthquake live on TV as they watched Game 3 at Candlestick Park.

The epicenter of the earthquake was located about 10 miles northeast of Santa Cruz on the Loma Prieta segment of the San Andreas fault system. I was on a commuter bus in Berkeley at the time; I didn’t feel a thing. But, many other people did.

More than 200 buildings were damaged in San Francisco’s Marina District. Forty-two people died when the upper level Cypress Street off-ramp of the Nimitz Freeway collapsed into the lower dock. Hundreds of Oakland residents were displaced when the buildings they lived in or worked in were closed because of structural damage.

Earthquakes are destructive. They cause property damage, injuries and loss of life. But, we can also learn a lot from earthquakes.

Earthquakes are caused by the interactions of tectonic plates. They generally occur at the boundaries where two or more plates meet. We can identify plate boundaries by mapping large amounts of earthquakes.

In this map, strong earthquakes from 2012-2014 are shown in red. Earthquakes from the last week are also shown.plateboundariesYou can see that most earthquakes occur in distinct bands. These bands outline the boundaries of Earth’s tectonic plates. The discovery that earthquakes occur in bands actually contributed to the idea of plate tectonics.

My students learn that there are three types of plate boundaries: divergent boundaries where plates move apart and new crust is formed; convergent boundaries where plates move together and oceanic crust is subducted or pushed down into the mantle; and, transform boundaries where plates move past each other. We can use earthquakes and volcanoes to determine the type of boundary at a map location.

When I added the Smithsonian Institutions Holocene volcanoes layer to the map, it looks like this. volcanoesThe yellow volcanoes are volcanoes that have been active over the last 10,000 years. As you can see, most of these volcanoes occur in the same area as earthquakes. There are some exceptions.

Volcanoes that occur far from plate boundaries are “hot spot” volcanoes. These form when crust travels over a mantle plume, an area in the mantle that is extra hot. Hawaii is a chain of hot spot volcanoes.Hawaii

There are also places where there are earthquakes an no volcanoes. The coast of California is one of those places.


In California, the San Andreas fault marks a transform boundary where the Pacific Plate is moving past the North American plate. Volcanoes only occur at divergent and convergent boundaries. The volcanoes to the east are extinct leftovers from Basin-Range rifting (divergent boundary).

We can use earthquake depth to determine if a map boundary is convergent or divergent. In this map, depth is shown by the size of the circle. Deeper earthquakes appear larger.


Shallow earthquakes (less than 75 km deep) often occur at mid-ocean ridges. These are long chains of underwater volcanoes where tectonic plates move apart and new crust is formed. Deep earthquakes occur at subduction zones where oceanic crust is being pushed under continental crust.


When this occurs, the subducting plate bumps and scrapes against the overriding plate. This causes deep earthquakes. When the subducting material reaches a depth of about 660 km, the rock becomes soft enough to flow and earthquakes stop.

Non-map images are from Creative Commons (Wikipedia). My map can be found here.

On Shaky Ground Part 1: Earthquakes in Virginia

It’s been just over four years since a 5.8 magnitude earthquake in the Central Virginia Seismic Zone damaged the Washington Monument. That was a significant earthquake for our area.

Last Sunday (9/27/15) the Central Virginia Seismic Zone experienced another earthquake.  The magnitude 2.0 quake was one of hundreds of small earthquakes that have occurred in the area over the past four years. And, InsideNova feels the need to report every single one.

So, is Virginia really a seismically active area? I placed esri’s USA Earthquake Risk map on top of a topographic base map. The map shows potential ground shaking intensity from earthquakes, an estimate of the amount of damage an earthquake is likely to cause in an area.  I set the scale so the highest risk in shown in dark red while the lowest risk appears as dark blue. I added the past week’s worth of earthquakes (from esri Disater Response) to the map. You can see the our 2.0 quake in Central Virginia.

Seismic zones

Moost of Virginia falls in the medium blue range indicating a very low risk of damage from earthquakes. Our recent earthquake is small compared to the many of the other earthquakes that occurred in the U.S. last week.

It’s not surprising that the West Coast of the United States is covered in red and orange. The California, Oregon, and Washington coasts are active margins. This means that the edge of the continent coincides with the edges of one or more tectonic plates (in this case: North American, Juan de Fuca, Pacific). Geologic activity such as earthquakes and volcanoes generally occurs at the edges of tectonic plates.

The East Coast is a passive margin. The eastern edge of the North American tectonic plate is far out in the Atlantic ocean. So, geologic activity on the East Coast and most of the U.S. is relatively rare as indicated by the blue coloring.

Behind California is an area known as the Basin Range province. This is the remnant of an ancient rift zone. In the early Miocene (about 17 ma), the North American continent began to stretch and thin. But, before the continent could rift into two tectonic plates, seismic activity stopped. This left a network of faults which still responds to the stresses from activity on the West Coast. The New Madrid fault zone which underlies Alabama, Arkansas, Illinois, Indiana, Kansas, Kentucky, Mississippi, Missouri, Oklahoma, Tennessee and Texas is another example of an ancient rift zone.

But, not all rift zones are ancient. The red area in Northern New York and New Hampshire indicates activity from the St. Lawrence rift system, an active rift zone that runs along the St. Lawrence River. Perhaps one day, North America will split and a new Canadian plate will form.

If you are looking carefully you might notice that there are medium blue areas in the middle of continents far from any plate boundaries that have recently experienced larger earthquakes. Is that rifting? Does that mean we should worry?

No, it’s not rifting, but we may have reasons to worry. The cluster of earthquakes in Oklahoma includes several with a magnitude between 2.0 and 3.0. These small earthquakes have been linked to fracking rather than seismic activity. The 3.2 earthquake near Stamford, NY may also be caused by human activity. It is likely the result of water pressure from the Gilboa Dam.

Like Oklahoma and New York, Virginia has networks of ancient faults that can be reactivated by human activity. However, seismologists believe that most of our earthquakes are simply the result of old faults moving because of sea floor spreading in the Atlantic Ocean.

You can view my map here.