Exogeology on Earth

Posted by Petra on 4th April 2010 in Petra's Blog

Yes, on Earth! Even though I mainly study other planets, Earth is a great place to see all sorts of geologic formations! Let me tell you about some great things to see on Earth that I’ve seen on the planets and moons.

Wait, craters on Earth? I thought there were only craters on the Moon! No, actually there can be craters on just about anything (as long as it has a solid surface; there aren’t craters on jovian planets). Earth has relatively few though, because smaller meteors burn up in our thick atmosphere. But some of the few meteor craters there are on Earth can be quite something to see! It’s almost like you’re on the moon! Barringer Crater in Arizona is the best example. Most craters on Earth are a bit less dramatic though, after being eroded for thousands of years. It gives you a great sense of what you’re dealing with to go and see a real crater.

Canyons are usually carved out by rivers, so why would they be in a list of exogeology related formations? After all, Earth is the only planet with such a large amount of water. Well, I’ve added them for a couple reasons. The first is that there are some formations that can best be described as canyons, even though they’re not made in the same way as the canyons we’re used to seeing. Take Mars’ Valles Marineris. It’s the largest canyon in the Solar System, but it’s a rift valley (a type of fault). On the other hand, there are channels on Mars that might have been made by the flow of water, like dried up riverbeds. I’ll talk about that more in a later post.

Ice fields are the only formation on this list I have yet to see. I’m actually going to be flying to Iceland for a few days to study glaciers. Because of this, posts over the next few days will be automated while I’m gone. Ice has been found all over: in comets and asteroids, on moons (Europa in particular), and on Mars. The gas giants are theorized to have icy cores. But not all this ice is actually frozen water. Europa might have water ice, but we don’t know for sure. Comets have water ice though. Water is so important on Earth that I think everything with water is exciting! Water is necessary for life, and that’s something I’d be thrilled to find. Could you imagine? I’m a huge science fiction fan, and that inspires me to think about big new scientific discoveries like life or undiscovered planets all the time. I’m getting off topic. Let’s get back to those awesome rocks!

Sand dunes can be found wherever there is sand, wind, and a dry climate. I went to the White Sands National Monument recently, and it was beautiful! As soon as you drove into the park there were sand dunes as far as you could see. The field of dunes was comparable to some of the dunes on Mars. An even better comparison is Utah’s Coral Pink Sand Dunes State Park. The reddish sand makes it feel as if you’re really on Mars. Dusty parts of deserts are also good places to look for dust devils, a common sight on the red planet.

Yes, I know, I was supposed to tell you about formations and not minerals. But minerals are important too! You need to look at the big things and the little things. There are a whole bunch of rocks and minerals that occur on Earth and also in space. One of my favorites is hematite. That’s an iron based mineral common on Mars. It comes in a few different forms. One form of hematite is red and rocky, and another is silvery gray and metallic. Iron in rocks is what makes Mars red! Moon rocks are pretty cool too; a rock from a lunar mare is made of the same thing as lava rocks on Earth! That ROCKS! 😉

Volcanoes have been found on Mars, Venus, Mercury, and Io. And on Titan there are cryovolcanoes! There are active and inactive volcanoes all over Earth that are fascinating to see in person. I try to go to as many volcano sites as I can during field research.

Plate tectonics is the process that makes the continents move. They spread apart like at the mid Atlantic ridge, and move under each other (called subduction) in places like Japan and the Aleutian islands of Alaska. The Earth’s surface is changing! And what’s more, there used to be plate tectonics on ancient Mars, and there still are on Titan!

Strata is just another term for rock layers. There are strata everywhere! That’s because rock layers can form all sorts of ways, like an ocean depositing sand on a beach or volcanoes erupting new lava flows. Strata can show a lot about that geographical area’s past. One time I looked at the strata in the Grand Canyon to figure out what order things happened in. I could easily see that the layers on the bottom formed first, then were tilted, and then that surface was eroded flat. More layers formed, and finally the Colorado River eroded the rocks away to create the Grand Canyon! How cool is it that you can tell what was happening for millions of years just by looking at rocks? I say that ROCKS! I do the exact same sort of thing when I look at strata from anywhere.

Can you believe so many of the same things happen on Earth that happen on other planets? I think it’s amazing. Exogeology ROCKS!

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