Activity discovered at Yellowstone Supervolcano - I talked about supervolcanos a while back. Don't worry, it's still in no danger of blowing up any time soon. (And here, we're talking geologically soon, which is a much, much longer span of time than a human soon.) The two cool things in this article are the discovery that the Tetons are getting shorter, and that there's a "bulge" that's expanded and deflated at Yellowstone.
The Tetons getting short is interesting because, in the normal course of things, mountains do get shorter. That's just the way things work. Mountains are built, erosion wears them down. However, the Tetons are getting shorter much, much faster than they ought to be. Now why is that? Mountain ranges are normally criss-crossed with faults, some of which may be very, very large. The faults are from where the rock broke, unable to handle the strain, when the mountain range was thrust up. There's a very large, active fault at the feet of the Tetons. The way such faults normally work when active is that the valley at the foot of the mountains drops, while the mountains move higher up. Except that the fault between the Tetons and their valley is going in the exact opposite direction as normal - the valley is rising, the mountains are sinking. It'll be interesting to find out what the exact mechanism is. The current hypothesis is that this abnormal movement is due to the expansion and contraction of the Yellowstone volcano; the volcano puffs up, it pushes on the valley. The valley creeps up the side of the mountains, which forces them down.
Now, the "bulge" is actually a pretty normal thing, volcano-wise. Contrary to what you might think, rock is actually very elastic. If put under pressure (pressure that isn't overwhelming, that is) for a long period of time, rocks will deform. When rocks are put under too much pressure too fast, they will break, which is what causes faults. Volcanoes tend to bulge as magma builds up, putting pressure on them from the inside. (One of the heralds of the Mt. Saint Helens eruption was the enormous bulge on the side of the mountain.) In many volcanoes, this bulge builds up and builds up until the volcano erupts. In this case, the bulge deflated a bit before rising again, which indicates a temporary relief of pressure; it also happened pretty rapidly - at seven inches in three years, that thing is sprinting when you think about things geologically. The bulge is probably caused by the movement of magma from the mantel plume that feeds Yellowstone.
* * *
Massive gypsum crystals in a cave in Mexico
These are SO COOL. Look at the first picture carefully - that's a person in there for scale. These crystals are in a limestone cave, which was probably created by water from a hydrothermal vent coming in through a fault and dissolving the rock. (Limestone is very prone to dissolve when in contact with water.) The water deposited the minerals that formed these crystals (and the precious metal veins exploited in a nearby mine) and the crystals formed over time. The area is still very active as a hydrothermal vent; the temperature of the cave is around 125-150F and the air's at a constant 100% humidity. Brutal!
If you didn't know, hydrothermal activity is associated with volcanic activity. When rock is subducted at a plate boundary, it normally carries a lot of water with it. The water is superheated and seperates from the rock; it escapes rapidly through whatever avenues are available to it, normally through faults that form vents. Due to the nature of how the rock melts, the superheated water often carries rare elements with it (such as precious metals) that it deposits along the vents as it cools, moving to the surface.
The giant crystals in this picture are gypsum. Gypsum is a pretty cool mineral. It's a 2 on Moh's hardness scale, which means that you can scratch it with your fingernail. When you get a nice crystal that hasn't been banged up (and it's hard to find those, sometimes, because just about anything will mark gypsum because it's so soft) they're usually transparent. When you touch gypsum, it's smooth and feels faintly soapy or waxy.
Monday, March 26, 2007
Wednesday, March 21, 2007
Arkose & Alluvial Fans
Today was my second field trip with my Sed Strat class. We went up to Settlers' Park to look at some exposed facies there. (A Facies is a group of sedimentary structures you see in a rock that points to a particular environment that the sediment was deposited in.) If you're ever in the Boulder area and up for a little bit of an uphill hike, I recommend it. The facies we looked at belonged to the Fountain Formation and the Lyons Formation.
The Fountain Formation is pretty famous, at least locally. A formation is a unit of rock that is geographically contiguous (it's all connected) and clearly seperate from the formations above and below. Sometimes this seperation is due to a change in rock type, since formations are usually of a single lithology - which is to say composed of just one type of rock. However, sometimes formations are seperated by unconformities, which are boundaries caused by erosion and other events.
So calling it the Fountain Formation means that it's a big unit of a single kind of rock that covers a definite geographical area. (In this case, a broad swath at the feet of the east face of the Rocky Mountains.) Fountain is the name of the formation. It is composed of sandstones and Arkose; the Arkose is the most famous and gives it its beautiful color. Arkose is a particular kind of sedimentary rock. Arkose is normally primarily quartz, but it has at least 25% Feldspar in it. This will give the rock a definite pink cast, or if its been exposed to any weathering, the Feldspar will cause iron oxide (remember: rust is iron oxide) that stains the rock anywhere from orange to a beautiful, deep red.
A large portion of the Fountain Arkose was deposited by alluvial fans. Alluvial fans are a phenomena found at the base of mountains. What happens is that there are canyons through the mountains - formed by rivers. During the spring melt (or intense storms), massive amounts of water will flood through these canyons, picking up lots and lots of sediment along the way. These canyons let out at the base of the mountains, and the water suddenly spills out in a characteristic fan-shape. (To visualize this, turn on a hose that's laying on the ground. Notice how the water spreads out in a fan at the end of the hose.)
While the water is shooting through the canyon, it's going very, very fast. This translates to the water having a lot of energy - and the more energy water has, the bigger rocks it can carry. As the water spills out of the canyon, it loses a lot of that velocity because it's no longer directed in a channel formed by the canyon walls. So it drops everything that it was carrying.
Alluvial fan deposits are very interesting to look at. They're composed of layer after layer of different kinds of mudstones, sandstones, and conglomerates. When the water first comes out of the canyon, it drops all of the big rocks that it picked up - anything from coarse sand to even boulders! The rocks formed from that are conflomerates - there's a wide range of how big the clasts (the bits of rock that the river dropped) are, and some of them are very large. At other times, the water wasn't moving fast enough to carry large rocks, and it will just drop sand, or even mud. So you will layers with all different clast sizes in them. Mudstones are often far darker than the layers above and below them, so you will see stripes running through the formation.
The Fountain Arkose formed from the erosion of the Ancestral Rocky Mountains - the mounains that existed in the past before today's Rockies. They were worn completely down, and then a new session of mountain building brought today's Rockies up. The Ancestral Rockies were made of granite as well - that's where the Feldspar in the Arkose comes from. Feldspar is an "unstable" mineral. It is subject to chemical weathering, and because of its physical properties, it breaks into tiny pieces easily. So large deposits of Feldspar are normally found close to their source. If they're buried quickly, they can't be weathered away!
If you want to see the Fountain Formation, there are many good places to see it in Colorado. In Boulder, you can go to Settlers' Park, where its been uplifted into a hogback - the originally flat layers of rock are standing vertically. Also in Boulder, the Flatirons are part of that formation. Red Rocks Amphitheatre is built in another exposure of the Fountain Formation. It can also be seen in Garden of the Gods. If you ever have a chance to go to any of these places, I recommend it. They're beautiful, and there's some good hikes in those areas along with great geology!
The Fountain Formation is pretty famous, at least locally. A formation is a unit of rock that is geographically contiguous (it's all connected) and clearly seperate from the formations above and below. Sometimes this seperation is due to a change in rock type, since formations are usually of a single lithology - which is to say composed of just one type of rock. However, sometimes formations are seperated by unconformities, which are boundaries caused by erosion and other events.
So calling it the Fountain Formation means that it's a big unit of a single kind of rock that covers a definite geographical area. (In this case, a broad swath at the feet of the east face of the Rocky Mountains.) Fountain is the name of the formation. It is composed of sandstones and Arkose; the Arkose is the most famous and gives it its beautiful color. Arkose is a particular kind of sedimentary rock. Arkose is normally primarily quartz, but it has at least 25% Feldspar in it. This will give the rock a definite pink cast, or if its been exposed to any weathering, the Feldspar will cause iron oxide (remember: rust is iron oxide) that stains the rock anywhere from orange to a beautiful, deep red.
A large portion of the Fountain Arkose was deposited by alluvial fans. Alluvial fans are a phenomena found at the base of mountains. What happens is that there are canyons through the mountains - formed by rivers. During the spring melt (or intense storms), massive amounts of water will flood through these canyons, picking up lots and lots of sediment along the way. These canyons let out at the base of the mountains, and the water suddenly spills out in a characteristic fan-shape. (To visualize this, turn on a hose that's laying on the ground. Notice how the water spreads out in a fan at the end of the hose.)
While the water is shooting through the canyon, it's going very, very fast. This translates to the water having a lot of energy - and the more energy water has, the bigger rocks it can carry. As the water spills out of the canyon, it loses a lot of that velocity because it's no longer directed in a channel formed by the canyon walls. So it drops everything that it was carrying.
Alluvial fan deposits are very interesting to look at. They're composed of layer after layer of different kinds of mudstones, sandstones, and conglomerates. When the water first comes out of the canyon, it drops all of the big rocks that it picked up - anything from coarse sand to even boulders! The rocks formed from that are conflomerates - there's a wide range of how big the clasts (the bits of rock that the river dropped) are, and some of them are very large. At other times, the water wasn't moving fast enough to carry large rocks, and it will just drop sand, or even mud. So you will layers with all different clast sizes in them. Mudstones are often far darker than the layers above and below them, so you will see stripes running through the formation.
The Fountain Arkose formed from the erosion of the Ancestral Rocky Mountains - the mounains that existed in the past before today's Rockies. They were worn completely down, and then a new session of mountain building brought today's Rockies up. The Ancestral Rockies were made of granite as well - that's where the Feldspar in the Arkose comes from. Feldspar is an "unstable" mineral. It is subject to chemical weathering, and because of its physical properties, it breaks into tiny pieces easily. So large deposits of Feldspar are normally found close to their source. If they're buried quickly, they can't be weathered away!
If you want to see the Fountain Formation, there are many good places to see it in Colorado. In Boulder, you can go to Settlers' Park, where its been uplifted into a hogback - the originally flat layers of rock are standing vertically. Also in Boulder, the Flatirons are part of that formation. Red Rocks Amphitheatre is built in another exposure of the Fountain Formation. It can also be seen in Garden of the Gods. If you ever have a chance to go to any of these places, I recommend it. They're beautiful, and there's some good hikes in those areas along with great geology!
Friday, March 02, 2007
Why you should love sedimentary rocks.
New year, new semester, new tax return, new FAFSA. Where does the time go?
Mineralogy last semester ended well, though I can't say I'm sorry to see it done. It takes a special kind of person to want to spend all your time staring into a petrographic microscope and thinking about 3-D crystalline forms. I got an A, and I wrote a rather boring paper about Enstatite, an igneous mineral that comes in rather pretty olive colored crystals. (Maybe I should post that paper here so you can look at it and... marvel, if that's the word I want.)
This semester, my geology course is sedimentary stratigraphy.
Sedimentary rocks are pretty much the unsung heroes of the modern age. Well, to be precise, rocks in general are unsung heroes. They just sort of lay there, as far as most people are concerned, and they don't actually do anything...
Except that they do. Off the top of my head, here's what rocks have done for you lately:
1) Kept you from plummeting into an ocean of subsurface magma.
2) Supported your house, roads, office building, etc.
3) Provided some pretty scenary, if you live near mountains.
4) Acted as building materials (or storage for building materials) for at least half the objects you interact with on a daily basis.
5) And so on and so on.
But among the rocks, sedimentary rocks are the work horses for human concern. Now, all rocks are linked together, by something called the rock cycle. Sedimentary rocks are formed by the weathering and erosion of igenous, metamorphic, and even other sedimentary rocks. Weathering is the process by which rock is broken down into little pieces, and erosion is how those little pieces are carried away, most commonly by water, followed by wind and gravity. These little rock pieces are called clasts; they're carried along by the wind or water and eventually dropped somewhere. This is called deposition. When enough clasts have been dropped in the same location, they build up, compact under their own weight, get covered with more clasts, and eventually get squished and cemented into a sedimentary rock.
That's the really simple, basic view of it.
Unlike igenous or metamorphic rocks, sedimentary rocks don't have to be melted or cooked or squished and twisted out of all recognizeable shape. This means that you find an absolute multitude of things in sedimentary rocks that you can't possibly find in metamorphic or igneous rocks. Things like: Fossils (bones and footprints and things like that), oil, and drinking water.
Sedimentary rocks often also preserve ingenious little clues that tell us a great deal about where they were formed and what the Earth was like at that time, and in that place. You can find ripples preserved in rocks, mud cracks, even the impression of rain drops falling on a desert plain in the distant past. These rocks are our window into a time so far back that human beings didn't exist to write down what was happening. Remember, in the lifetime of the earth, we are barely the blink of an eye.
So, every time you go to the museum and look at the dinosaur bones, you're looking at something that was preserved in a sedimentary rock. Every time you put gas in your car, you're using a product made from oil, which forms in shale (a sedimentary rock formed in deep water conditions), and then hides in subsurface reservoirs, most of them found in either sandstone or limestone (also sedimentary rocks). If you drink water from an aquifer, that water often has filtered a long distance through a formation of sandstone, which has acted as a natural filter so it's clean to drink.
Isn't that a weird though, water or oil flowing through rocks? In some of these reservoirs, it's just finding its way through cracks in the rock. But in the case of sandstone, it is literally travelling through the rock. This is because of the way sandstone is made.
Sandstone is made of sand-sized clasts. Now, these clasts can really be any sort of rock or mineral, but most commonly you'll find them made of quartz. This is because quartz is pretty hard, and has a property called conchoidal fracture. That means that when a little piece of quartz gets rolled or bumped along by the wind or water, it breaks in a special way. It doesn't get sharp corners - it breaks in a very round, smooth fashion. So quartz sand, once its old enough and has been moved around enough, tends to be the roundest, smoothest sand you'll ever find. Then when you pack this quartz sand together, there's space between the little sand grains. Think about what it looks like when you put a bunch of marbles in a bowl. There's still plenty of space in between the marbles for liquid to fit in, even if they're packed as tightly as possible.
So, when you get a whole load of these quartz sand grains together and pack them in tightly, then squish them some more and cement them together to make a piece of sandstone, even if the rock looks solid, there's actually a lot of empty space in it, hiding between the quartz grains!
This space is what oil and water move through. So when someone drills a well down to contact the sandstone the oil or water is in, it happily moves into the well - because the pressue in a well that goes all the way to the surface is a lot less than the pressure all that oil or water is under when it's in a rock, under the ground.
There's a lot more to talk about with sedimentary rocks. Hopefully I'll be able to ramble about them some more, soon!
Mineralogy last semester ended well, though I can't say I'm sorry to see it done. It takes a special kind of person to want to spend all your time staring into a petrographic microscope and thinking about 3-D crystalline forms. I got an A, and I wrote a rather boring paper about Enstatite, an igneous mineral that comes in rather pretty olive colored crystals. (Maybe I should post that paper here so you can look at it and... marvel, if that's the word I want.)
This semester, my geology course is sedimentary stratigraphy.
Sedimentary rocks are pretty much the unsung heroes of the modern age. Well, to be precise, rocks in general are unsung heroes. They just sort of lay there, as far as most people are concerned, and they don't actually do anything...
Except that they do. Off the top of my head, here's what rocks have done for you lately:
1) Kept you from plummeting into an ocean of subsurface magma.
2) Supported your house, roads, office building, etc.
3) Provided some pretty scenary, if you live near mountains.
4) Acted as building materials (or storage for building materials) for at least half the objects you interact with on a daily basis.
5) And so on and so on.
But among the rocks, sedimentary rocks are the work horses for human concern. Now, all rocks are linked together, by something called the rock cycle. Sedimentary rocks are formed by the weathering and erosion of igenous, metamorphic, and even other sedimentary rocks. Weathering is the process by which rock is broken down into little pieces, and erosion is how those little pieces are carried away, most commonly by water, followed by wind and gravity. These little rock pieces are called clasts; they're carried along by the wind or water and eventually dropped somewhere. This is called deposition. When enough clasts have been dropped in the same location, they build up, compact under their own weight, get covered with more clasts, and eventually get squished and cemented into a sedimentary rock.
That's the really simple, basic view of it.
Unlike igenous or metamorphic rocks, sedimentary rocks don't have to be melted or cooked or squished and twisted out of all recognizeable shape. This means that you find an absolute multitude of things in sedimentary rocks that you can't possibly find in metamorphic or igneous rocks. Things like: Fossils (bones and footprints and things like that), oil, and drinking water.
Sedimentary rocks often also preserve ingenious little clues that tell us a great deal about where they were formed and what the Earth was like at that time, and in that place. You can find ripples preserved in rocks, mud cracks, even the impression of rain drops falling on a desert plain in the distant past. These rocks are our window into a time so far back that human beings didn't exist to write down what was happening. Remember, in the lifetime of the earth, we are barely the blink of an eye.
So, every time you go to the museum and look at the dinosaur bones, you're looking at something that was preserved in a sedimentary rock. Every time you put gas in your car, you're using a product made from oil, which forms in shale (a sedimentary rock formed in deep water conditions), and then hides in subsurface reservoirs, most of them found in either sandstone or limestone (also sedimentary rocks). If you drink water from an aquifer, that water often has filtered a long distance through a formation of sandstone, which has acted as a natural filter so it's clean to drink.
Isn't that a weird though, water or oil flowing through rocks? In some of these reservoirs, it's just finding its way through cracks in the rock. But in the case of sandstone, it is literally travelling through the rock. This is because of the way sandstone is made.
Sandstone is made of sand-sized clasts. Now, these clasts can really be any sort of rock or mineral, but most commonly you'll find them made of quartz. This is because quartz is pretty hard, and has a property called conchoidal fracture. That means that when a little piece of quartz gets rolled or bumped along by the wind or water, it breaks in a special way. It doesn't get sharp corners - it breaks in a very round, smooth fashion. So quartz sand, once its old enough and has been moved around enough, tends to be the roundest, smoothest sand you'll ever find. Then when you pack this quartz sand together, there's space between the little sand grains. Think about what it looks like when you put a bunch of marbles in a bowl. There's still plenty of space in between the marbles for liquid to fit in, even if they're packed as tightly as possible.
So, when you get a whole load of these quartz sand grains together and pack them in tightly, then squish them some more and cement them together to make a piece of sandstone, even if the rock looks solid, there's actually a lot of empty space in it, hiding between the quartz grains!
This space is what oil and water move through. So when someone drills a well down to contact the sandstone the oil or water is in, it happily moves into the well - because the pressue in a well that goes all the way to the surface is a lot less than the pressure all that oil or water is under when it's in a rock, under the ground.
There's a lot more to talk about with sedimentary rocks. Hopefully I'll be able to ramble about them some more, soon!
Wednesday, December 06, 2006
Liquid Water on Mars
NASA has just released a statement saying that they've got good evidence of liquid water making an appearence on Mars some time in the last seven years.
BBC News Story
This is very exciting for several reasons. There is water on Mars that we know of, but it's all locked in ice. (As an aside, did you realize that ice is a mineral? It's the lowest density mineral that occurs on Earth.) But the most likely cause of this new gully that you can see in the photograph is liquid water! Liquid water is important because it's necessary for life as we know it (so it once again introduces the possibility that we may some day find some sort of single-celled life on the red planet) and it's also very important if we ever want to consider the possibility of building some sort of base or research station on Mars. We need a lot of water to survive, and it would make getting there and setting up shop a lot easier if we didn't have to haul all of the water necessary with us.
Now, there has been evidence suggesting liquid water, though all of that was for much less recent events. A lot of the erosional forms on the surface of the planet point toward liquid water, though it could also be argued that the erosion could be caused by wind as well. (If you're not actually there to look at things, it can be very difficult to tell the difference between erosion caused by liquid, wind, and simple wasting of loose material.) And there still is a possibility that this new gully was caused by mass wasting or even liquid carbon dioxide.
But liquid water is currently the best explanation.
This is all very exciting stuff!
High resolution images from the Mars Global Surveyor.
Phil Plait comments.
BBC News Story
This is very exciting for several reasons. There is water on Mars that we know of, but it's all locked in ice. (As an aside, did you realize that ice is a mineral? It's the lowest density mineral that occurs on Earth.) But the most likely cause of this new gully that you can see in the photograph is liquid water! Liquid water is important because it's necessary for life as we know it (so it once again introduces the possibility that we may some day find some sort of single-celled life on the red planet) and it's also very important if we ever want to consider the possibility of building some sort of base or research station on Mars. We need a lot of water to survive, and it would make getting there and setting up shop a lot easier if we didn't have to haul all of the water necessary with us.
Now, there has been evidence suggesting liquid water, though all of that was for much less recent events. A lot of the erosional forms on the surface of the planet point toward liquid water, though it could also be argued that the erosion could be caused by wind as well. (If you're not actually there to look at things, it can be very difficult to tell the difference between erosion caused by liquid, wind, and simple wasting of loose material.) And there still is a possibility that this new gully was caused by mass wasting or even liquid carbon dioxide.
But liquid water is currently the best explanation.
This is all very exciting stuff!
High resolution images from the Mars Global Surveyor.
Phil Plait comments.
Thursday, November 30, 2006
HiRISE is made of win.
Finals are about to eat my brain. I had no idea school was just so exhausting.
But this cheers my day - and hopefully will cheer yours too!
HiRISE
High resolution images of the surface of Mars, some in color, some in grayscale. The files are enormous, and worth it. You end up with a single pixel being about a meter on the ground - which is AMAZING, considering that we're talking about Mars, here. Some of topography is just stunning.
Being able to look at geological structures on the surface of Earth is cool enough. But we can really start comparing to what we're seeing on Mars. It'll give us some ideas of how certain features on the Martian surface formed, which will answer a lot of questions. (Though there's a big one we'll probably need to get in closer to answer - was the agent of erosion water or wind?)
Seeing all of this information streaming in from Mars gives me a lot of hope. My dream is that some day we'll be able to send up some seismic instrument packages, though that will take a lot of doing. But think about it - being able to take a look at the subterranian geologic structure, and what that could tell us about the history of the planet. (And that would just be scratching the surface!) Some day, I hope... some day.
But this cheers my day - and hopefully will cheer yours too!
HiRISE
High resolution images of the surface of Mars, some in color, some in grayscale. The files are enormous, and worth it. You end up with a single pixel being about a meter on the ground - which is AMAZING, considering that we're talking about Mars, here. Some of topography is just stunning.
Being able to look at geological structures on the surface of Earth is cool enough. But we can really start comparing to what we're seeing on Mars. It'll give us some ideas of how certain features on the Martian surface formed, which will answer a lot of questions. (Though there's a big one we'll probably need to get in closer to answer - was the agent of erosion water or wind?)
Seeing all of this information streaming in from Mars gives me a lot of hope. My dream is that some day we'll be able to send up some seismic instrument packages, though that will take a lot of doing. But think about it - being able to take a look at the subterranian geologic structure, and what that could tell us about the history of the planet. (And that would just be scratching the surface!) Some day, I hope... some day.
Tuesday, October 03, 2006
70 million year old soft tissue.
Remember: scientists love it when the impossible happens. (At least when the impossible happens in an observable, empirical fashion.) It's time for us to rethink our understanding of the process of fossilization. As we understand it now, this would have been impossible - but it happened! So now we need to work out the how and why. This is so COOL!
And here it is - soft tissue found with a 70 million year old fossilized dinosaur bone! A T-rex bone, to be precise. This is beyond cool. It means that they can do some biological comparisons between the Big T and birds, and they may even be able to sequence its DNA. Don't worry, there's a BIG difference between knowing an animal's DNA and being able to clone it, so we won't be seeing Jurassic (or in this case Cretaceous) park any time soon.
Scientists recover T-Rex soft tissue.
And here it is - soft tissue found with a 70 million year old fossilized dinosaur bone! A T-rex bone, to be precise. This is beyond cool. It means that they can do some biological comparisons between the Big T and birds, and they may even be able to sequence its DNA. Don't worry, there's a BIG difference between knowing an animal's DNA and being able to clone it, so we won't be seeing Jurassic (or in this case Cretaceous) park any time soon.
Scientists recover T-Rex soft tissue.
Tuesday, September 26, 2006
What the space shuttle has done for you lately.
Yep, the space shuttle. And yet, it must be geology related - I'm writing about it, aren't I?
There's a nifty piece over at the Planetary Society blog about the Shuttle Radar Topography Mission. Basically, they got near-global topographical maps of the Earth out of this - more detailed than ever before!
Topography is very important to geology. It helps you figure out what's lurking beneath the surface, and what forces might have acted to create the surface in the first place!
There's a bunch of nifty links at the bottom of the article, which point to several specific pages of what they've figured out with the data. I suggest looking at the one about the rift valley in Tanzania and Mount St. Helens, since both are near and dear to my heart. But all of the information is way cool. (And some, like the information about New Orleans and its flood, is way important too.)
There's a nifty piece over at the Planetary Society blog about the Shuttle Radar Topography Mission. Basically, they got near-global topographical maps of the Earth out of this - more detailed than ever before!
Topography is very important to geology. It helps you figure out what's lurking beneath the surface, and what forces might have acted to create the surface in the first place!
There's a bunch of nifty links at the bottom of the article, which point to several specific pages of what they've figured out with the data. I suggest looking at the one about the rift valley in Tanzania and Mount St. Helens, since both are near and dear to my heart. But all of the information is way cool. (And some, like the information about New Orleans and its flood, is way important too.)
Friday, September 08, 2006
Time for a little juvenile humor.
Ready for some geology humor? Of course you are!
While doing my mineralogy homework today, I discovered that there's a fun mineral, called Realgar. It's very pretty, which deep red, prismatic crystals. (Prismatic means that it forms with very flat surfaces.)
Realgar is Arsenic Sulfide. Which, if you know your periodic table, you'll be way ahead of me here...
AsS!
Yes, that's the chemical formula. I got a geeky giggle out of that.
Go here if you'd like to find out more about crystalline AsS! It's actually a lot prettier than you'd think.
I've got another geeky geology joke to tell you, but for now, I'd better get back to my homework.
While doing my mineralogy homework today, I discovered that there's a fun mineral, called Realgar. It's very pretty, which deep red, prismatic crystals. (Prismatic means that it forms with very flat surfaces.)
Realgar is Arsenic Sulfide. Which, if you know your periodic table, you'll be way ahead of me here...
AsS!
Yes, that's the chemical formula. I got a geeky giggle out of that.
Go here if you'd like to find out more about crystalline AsS! It's actually a lot prettier than you'd think.
I've got another geeky geology joke to tell you, but for now, I'd better get back to my homework.
Thursday, August 31, 2006
Touching history.
Just a short one - I'm still alive, I swear. School just started, which is very exciting. I'm taking Mineralogy, which thus far has been a very exciting class. We're doing "Adopt a mineral" where we pick out a mineral at the start of class, and write a paper about it at the end. Mine is a variety of Olivine, which is a very neat mineral, so expect to hear more about it in the future.
I'm rushed right now, though, so just a quick one.
Today we were talking about physical properties (more on that later), and my professor brought out a piece of a meteorite to pass around. It had been cut neatly from the main body of the meteorite. So one surface was polished to a dark, metallic shine, and the other side was all whorls and bumps, rough and rusty black. It was a lot heavier than I expected - iron and nickel with just a few traces of other minerals.
That piece of meteorite was 4.5 billion years old, which makes it older than the oldest rock discovered thus far on the earth. (Which is a piece of metamorphic rock that is, I believe 4.4 billion years old.) And this rock had hurtled through space, across unknown, cast distances, and then torn its way through our atmosphere to impact in Africa.
As I looked at the rough side of the rock slice, I felt true awe. What kind of story could a rock tell, of 4.5 billion years. Where had it been. Even trying to imagine that sort of antiquity is impossible for the human mind, really. We can only grasp numbers up to a certain point, and then it just becomes more than we can understand.
This is why I think geology is so exciting. If you believe in a god, of whatever sort, this is what it's like to reach out and try to touch it.
I'm rushed right now, though, so just a quick one.
Today we were talking about physical properties (more on that later), and my professor brought out a piece of a meteorite to pass around. It had been cut neatly from the main body of the meteorite. So one surface was polished to a dark, metallic shine, and the other side was all whorls and bumps, rough and rusty black. It was a lot heavier than I expected - iron and nickel with just a few traces of other minerals.
That piece of meteorite was 4.5 billion years old, which makes it older than the oldest rock discovered thus far on the earth. (Which is a piece of metamorphic rock that is, I believe 4.4 billion years old.) And this rock had hurtled through space, across unknown, cast distances, and then torn its way through our atmosphere to impact in Africa.
As I looked at the rough side of the rock slice, I felt true awe. What kind of story could a rock tell, of 4.5 billion years. Where had it been. Even trying to imagine that sort of antiquity is impossible for the human mind, really. We can only grasp numbers up to a certain point, and then it just becomes more than we can understand.
This is why I think geology is so exciting. If you believe in a god, of whatever sort, this is what it's like to reach out and try to touch it.
Wednesday, August 16, 2006
Polar Wandering
No, it's not about poor explorers wandering across a featurless plain of snow, searching for the South Pole so they can have bragging rights to go with their frostbite when they get home.
I've been wanting to write about this for a while, just because it's so cool!
It starts out very simply. There's a mineral, called Magnetite. As the name indicates, it is magnetic, and naturally so. In fact it's the most magnetic mineral on the planet. If you've ever heard of lodestones - which were used to make the earliest compasses - those are actually pieces of magnetite. Magnetite is an important source of iron ore, and is also used to "blue" steel to prevent it from rusting.
Magnetite can form in significant amounts, but more importantly, it's present in at least small amounts in almost all igneous rocks. Igneous rocks (in case you don't remember from grade school, which is the last time most of us had geology) are the ones that form directly from molten rock. They flow and explode from volcanoes, but also cool slowly beneath the surface of the earth in upwellings of magma from the mantle. There are a lot of igneous rocks in the world, and they're pretty durable. This means that there are a lot of igneous rocks around for us to look at, and some of them are billions of years old.
Igneous rock forms when magma (or lava, which is what we call magma when it's on the surface) cools completely. As the melted rock cools, all of the different minerals that have been mixed together in it start to group up and form crystals. If you've ever seen sugar crystals "grown" when you put a stick in a glass of sugary water, it's exactly the same idea. At that point, they're fixed in place and don't change position until the rock is destroyed by either being melted again (geologic recycling!) or eroded away.
Okay, so what does any of this have to do with Polar Wandering... whatever that is.
Because Magnetite is magnetic, when it crystalizes, it points toward the magnetic north pole. And once it is crystalized, it can't move. So you can look at it as a record, a photo of a little finger pointing north, indellibly etched with the date and time. At this moment in history, north was this way.
All very well and good, but north has always been north, right? So who cares?
Well, what if I told you that north hasn't always been north? Oho!
Once we (meaning geologists) were able to examine the little crystals of magnetite to see what direction they were pointing, we discovered something very strange. In the different layers of igneous rock, the little bits of magnetite had a serious disagreement over which direction was north. Now, keep in mind that when you have different layers of rock, that means different ages of rock. The oldest ones are at the bottom, and then they get younger as you move toward the surface.
So, for example:
Rock layer #1 (the youngest) said that north was this way: /
Rock layer #2 (the middle) said that north was this way: |
Rock layer #3 (the oldest) said that north was this way: --
Well, how does that work? Magnetite doesn't lie. When those crystals formed, they really did point toward north. After a lot of head scratching, the first thought was that maybe the magnetic north pole has moved over time, wandering across the surface of the Earth. (Whence, polar wandering, which can be plotted as a curved line across the planet.) It sounds kind of weird, but there had to be some explanation for what we'd seen. And science is very much about observing strange things in nature and then figuring out what might have caused them.
But then things got even weirder. We looked at magnetite from a different place - and entirely different continent. If the magnetic north pole had really gone meandering across the Earth, then the magnetite on that continent would agree.
Only... it didn't.
We found rocks that were the same age as the first ones we looked at, and the little bits of magnetite helpfully pointed out that north was in a completely different direction from what the other ones said. And then we went to another continent and got a third set of answers that were different from the first two. And so on, and so on.
We sat back and scratched out heads. Every continent had a different path for the north pole to have wandered down throughout history. Did that mean that in the past, every continent had its very own north pole? That sounds pretty silly to begin with, and, well, right now we've obviously got only one north pole. The way the world works hasn't suddenly changed just because humans discovered how to make compasses.
But... what if the continents themselves had moved? North had stayed the same (except of course when it switched places with the south pole, but that's a subject for a different post) but the continents had wandered across the face of the planet, drifting and rotating.
That was the only explanation we had that fit the facts and followed the main principle of modern geology - that the geological forces and events that we see today are the same ones that shaped the world in the past.
Polar wandering is one of the strongest pieces of evidence for the theory of continental drift - the theory of plate tectonics. And since the time that scientists decided that having a multitude of wandering north poles was just plain silly, more evidence has been found to support the idea of continental drift. Today, we have satellites and other machines that can measure things so precisely that we can see the continents move. Some of them move as fast as six centimeters in a single year. To us, that sounds horribly slow, but think how much movement that adds up to in a billion years.
The ground beneath your feet is moving. We drift slowly across a sea of molten rock, even as the Earth spins out its days and rockets around the sun.
Now, how cool is that?
I've been wanting to write about this for a while, just because it's so cool!
It starts out very simply. There's a mineral, called Magnetite. As the name indicates, it is magnetic, and naturally so. In fact it's the most magnetic mineral on the planet. If you've ever heard of lodestones - which were used to make the earliest compasses - those are actually pieces of magnetite. Magnetite is an important source of iron ore, and is also used to "blue" steel to prevent it from rusting.
Magnetite can form in significant amounts, but more importantly, it's present in at least small amounts in almost all igneous rocks. Igneous rocks (in case you don't remember from grade school, which is the last time most of us had geology) are the ones that form directly from molten rock. They flow and explode from volcanoes, but also cool slowly beneath the surface of the earth in upwellings of magma from the mantle. There are a lot of igneous rocks in the world, and they're pretty durable. This means that there are a lot of igneous rocks around for us to look at, and some of them are billions of years old.
Igneous rock forms when magma (or lava, which is what we call magma when it's on the surface) cools completely. As the melted rock cools, all of the different minerals that have been mixed together in it start to group up and form crystals. If you've ever seen sugar crystals "grown" when you put a stick in a glass of sugary water, it's exactly the same idea. At that point, they're fixed in place and don't change position until the rock is destroyed by either being melted again (geologic recycling!) or eroded away.
Okay, so what does any of this have to do with Polar Wandering... whatever that is.
Because Magnetite is magnetic, when it crystalizes, it points toward the magnetic north pole. And once it is crystalized, it can't move. So you can look at it as a record, a photo of a little finger pointing north, indellibly etched with the date and time. At this moment in history, north was this way.
All very well and good, but north has always been north, right? So who cares?
Well, what if I told you that north hasn't always been north? Oho!
Once we (meaning geologists) were able to examine the little crystals of magnetite to see what direction they were pointing, we discovered something very strange. In the different layers of igneous rock, the little bits of magnetite had a serious disagreement over which direction was north. Now, keep in mind that when you have different layers of rock, that means different ages of rock. The oldest ones are at the bottom, and then they get younger as you move toward the surface.
So, for example:
Rock layer #1 (the youngest) said that north was this way: /
Rock layer #2 (the middle) said that north was this way: |
Rock layer #3 (the oldest) said that north was this way: --
Well, how does that work? Magnetite doesn't lie. When those crystals formed, they really did point toward north. After a lot of head scratching, the first thought was that maybe the magnetic north pole has moved over time, wandering across the surface of the Earth. (Whence, polar wandering, which can be plotted as a curved line across the planet.) It sounds kind of weird, but there had to be some explanation for what we'd seen. And science is very much about observing strange things in nature and then figuring out what might have caused them.
But then things got even weirder. We looked at magnetite from a different place - and entirely different continent. If the magnetic north pole had really gone meandering across the Earth, then the magnetite on that continent would agree.
Only... it didn't.
We found rocks that were the same age as the first ones we looked at, and the little bits of magnetite helpfully pointed out that north was in a completely different direction from what the other ones said. And then we went to another continent and got a third set of answers that were different from the first two. And so on, and so on.
We sat back and scratched out heads. Every continent had a different path for the north pole to have wandered down throughout history. Did that mean that in the past, every continent had its very own north pole? That sounds pretty silly to begin with, and, well, right now we've obviously got only one north pole. The way the world works hasn't suddenly changed just because humans discovered how to make compasses.
But... what if the continents themselves had moved? North had stayed the same (except of course when it switched places with the south pole, but that's a subject for a different post) but the continents had wandered across the face of the planet, drifting and rotating.
That was the only explanation we had that fit the facts and followed the main principle of modern geology - that the geological forces and events that we see today are the same ones that shaped the world in the past.
Polar wandering is one of the strongest pieces of evidence for the theory of continental drift - the theory of plate tectonics. And since the time that scientists decided that having a multitude of wandering north poles was just plain silly, more evidence has been found to support the idea of continental drift. Today, we have satellites and other machines that can measure things so precisely that we can see the continents move. Some of them move as fast as six centimeters in a single year. To us, that sounds horribly slow, but think how much movement that adds up to in a billion years.
The ground beneath your feet is moving. We drift slowly across a sea of molten rock, even as the Earth spins out its days and rockets around the sun.
Now, how cool is that?
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