Geoscience Education in the Mountain State:
CATS Environmental Geology Telecourse, Fall 1999,
Show 2 Transcript

CATS Telecourse
Environmental Geology
September 27, 1999

Dr. Bob: Greetings! Welcome again to another in house sessions and seeing you all out there. Deb we've been talking here in the studio about the flooding in North Carolina. It's an environmental disaster of incredible proportions. It's a situation where a tremendous number of animals, the carcasses have been out for many days now. They can't be used for pet food and they have over a million birds to have to burn, over a 100,000 hogs. There are 60 of the 3700 lagoons for animal waste treatment that overflowed or flooded. One actually gave way so that 2 million or so gallons of water joined in to the rest of the flood mix with not only silt and clay but also pesticides, solvents, gasoline, paints and other various materials. It's a two year disaster. It will take a year or two years to really bring things back up in many places. Estimates now are over a billion dollars of agricultural damage and what is yet to be resolved is just how much damage has been done to the shellfish industry and other seafood industry in Pamlico Sound. Then further north in the Chesapeake Bay. Nine states have been put on the Federal Disaster Relief Agenda from this particular storm and from many other types of storms and events. Nine states might be a record from one type of event. It's truly an environmental disaster of enormous proportions.

Today (goes to overhead) we'll have just a brief look at the outline. Then start talking about plate tectonics, boundaries, hot spots, and the engine that drives the system. We'll have a break and we'll go into things that bump in the night. If you had heard the old Scottish statement of "ghoulies, ghosties, and long leggity beasties, and things that go bump in the night, good lord deliver us." The things that go bump in the night, after the break, earthquakes and volcanoes. Earthquakes being very much an event in the news. Another after shock again in Taiwan after their rather massive earthquake and the after shock caused directly three more deaths to the 3,000 total. In Turkey, just a few weeks back, tremendous number of loss of life.

Just as a little note as to where everybody is viewing us, here is the outline of West Virginia, and those are our sites. The counties are designated by sites. We have over 100 people involved for credit or noncredit in this session. We are beaming all over the state and we'll get right to it and talk about plate tectonics. But first Deb, we really should talk about the exploratory. The first exploratory comes up this weekend. How are we going to do this? This one's in Parkersburg.

Dr. Deb: We'll meet at Parkersburg. You have your choice of one of two sessions, essentially. We have a session that starts at Friday noon and extends into Saturday. Another session that starts Saturday noon and goes to Sunday. We'll be meeting at the Holiday Inn which is the crossroads of Rt. 50 and I-77. You need to pick one of those two to attend. We have room for fifty on Friday to Saturday. We have room for 30 on the Saturday to Sunday. You need to let your facilitator know tonight. If you don't know tonight then you need to either e-mail or phone Tom Repine at the Geological Survey using the 1-800-WVGEOLOgy and let him know which one of those you plan to attend. We need to know ahead of time where you're going to be because of the limit of rooms.

Dr. Bob: The rooms will be held but then we'll have to cancel out if we're not going to use any of the rooms. We do need to have your commitment to one of those two. On Saturday we will end about 3 to 4 so there's time for those folks to drive home. Each of the evenings, Friday nights there's a session that we have and Saturday night a session that we will replicate for those who are there. We'll do map work and a variety of things in those two evening sessions. They will be exactly the same for both evening sessions. The full trip will be tweaked a little bit based on the availability of entre into certain locations but you will still get a great cross section of activities and actually seeing things, sketching. Bring your camera if you have it. That could be of critical value to you and bringing back to the classroom some of the pictures that we'll see. Also, we have ordered and reordered books with the hundred or so folks we've been pleasantly overwhelmed. They should be in your hands by the next time that we meet together. The registration at WVU has to be in by this Thursday, so get all your material in by Thursday. If you have any questions call Tom or talk to your facilitator. WVU works on certain deadlines and we've seen this in the past that if we miss these deadlines you don't want to get caught up in what some might view as a very inflexible computer system for registration at WVU. Obviously it is flexible because we are in October and finally finishing up registration but we can't go too much longer otherwise the door is shut. Also, there will be a quiz. It will be up on the Web site tomorrow morning. It will be based on the last session that we had two weeks ago and tonights discussion. That will be available. There's a revised syllabus with deadlines and information on the Web site. You can just answer right into the Web site and then download the information at the Survey and Tom Repine will be able to pick that up. We do not have that facility at WVU. It all goes through the Survey. This is truly an important cooperative effort. Always keep a copy for yourself. There was only one piece that got caught up electronically and didn't go through. Those are the housekeeping chores. Also, every time we get together there will be a quiz the next morning. Each one averages out to be worth 25 points, a total of 100 points. You can use books and notes. You can talk to each other in the session or after the session but each one is to do their own work to submit the information on the quizzes.

Tonight we have the topic that in most of geology now has become the underlying theme. For many, many years in the early start of geology it was just very much descriptive. We saw rocks and fossils, we interpreted them but we did not have in the science of geology a unifying theory. Chemistry, biology, physics, they were built on strong theories. Theories that were tested and evaluated. It was not until this century that geology started to look for some really big pictures to go at. It really didn't come, as we'll find in a brief history in a few moments, to the front of science until after WWII. It took some of the electronic devices and materials, equipment that was developed for the war, to be applied over to oceanographic research and geologic research in general. In order for us to really grasp the fact that we had on our hands in geology very much a unifying theory. This unifying theory, while it helps to explain and is tested for the explanation of the earth, also the plate tectonics relates to the environment and the things that we go through.

In your experience Deb, "What sort of ways have you handled in working with students on plate tectonics?"

Dr. Deb: There's a variety of classroom applications for plate tectonics. If you're trying to get the motion of the plates and trying to describe how the plates move on convection cells then a really classic demonstration is to take a glass bread pan and place it on little wooden blocks. Then put a votive candle beneath that. You light it and let it go for awhile, till the water heats up and then have the students put a drop of food coloring or two in there. They can watch as the convection cells are marked by the dye as they start to move through the water. If you place a small packet of tea leaves on top and you can watch as the tea starts to move across. It's a very good demonstration for plate tectonics and the motion of plates on the convection cells.

Dr. Bob: Convection cells and the plate tectonic theory itself, some of the early views were in watching the lava flows in Hawaii. Watching the material that cooled on the surface, especially at night, you can see these plates cool, move off, and then as they cool they get a little bit more dense and they start to sink underneath. Where they pull apart, there's a new uprising of red hot or yellow hot magma. This is a nice replica, you can't bring lava into the classroom, doesn't work out well at all.

One of the other things, so often we talk about the jigsaw fit but it depends on what type of maps you have and what projection or if you actually have a globe where you can move things around. How do you handle that?

Dr. Deb: The classic Pangea puzzle lab has been used for a long time now. That's where the students cut out the continents and the teacher tasks them to put them together to form a continent, Pangea. Invariably they don't get it right. Not that you're looking for a right answer but you get a variety of fits. They generally do get South America and Africa pieced together, but from there on it's just total chaos as to where the continents are going. That's a nice introduction to the fact that the continents can fit together but you certainly don't want to leave it there. You want to build on that, talk about Pangea, talk about Alfred Wegner's evidence for continental drift and then give them another task. That is getting those back but this time put clues on the continents, like fossil evidence, Glossopteris or lystrosaurus or glacial striations or mountains that might match up and have them do it again. This time they can talk about how much easier or more accurate it is when you have evidence to base your puzzle as opposed to coastlines that have been eroded or changed or inundated by water.

Dr. Bob: (Goes to overhead) We have a map here and to expand upon that, one of the real problems is that Central America didn't exist. It isn't part of the picture, the old continents. Further, we're talking about continental shelves, very few of our students at any age have a real understanding of where's the edge of the continent. If it's underwater they can't see it from there. As you've said, South America and Africa are a great start. Then, the northwest corner of Africa and North America is a real nice start but if Australia is kind of attached like an appendix out there, it's going to spin around and rotate, or Antarctica, India. There's a whole portion of Antarctica that doesn't fit either because it's new. If you think of Antarctica today on a global projection just looking at the pole, you'll see a like a big catchers mitt. The whole thumb of the catchers mitt is geologically very new. It's not that old, old continent stuff. What dinosaur book was it that had such excellent portrayal of some additional information?

Dr. Deb: Craig Munsart's (sp) dinosaur book had a fairly nice model for high school students to use. It had the glacial striations marked, rock types labeled, fossil evidence listed also, but it certainly isn't something you'd want to use for the elementary grades. There is a fairly decent elementary version of this same thing found in the "Earth Model Book" by Scholastica. If you would like that citation I can provide it for you, you can e-mail me and I'll get back to you.

Dr. Bob: I'm just real happy if they do South America and Africa. So much of the rest is of value but it's a detail that you just aren't that familiar with.

The next component of this is we're talking about plates. We're talking about hard stuff, brittle stuff, on the skin of the earth. Many times they suggest using an apple as a model of the earth. The actual skin of the apple if reasonably to scale to the lithosphere or brittle part, then the mantle, the good eating part of the apple, and then the core is the core of the earth.

Dr. Deb: I don't like that model, I like the peach. It's got a pit in the middle of it which could be the outer inner core. So it's more appropriate.

Dr. Bob: That's true. The key point is to somehow at any age have youngsters be startled by the fact that we're really looking at a very, very thin outer portion. It is unimaginably thick by our dimensions, Ok. If there were stairs to the bottom of the lithosphere, this brittle part, we'd be walking down stairs for a long, long time. If there was an elevator we'd be rattling around in that elevator for a long, long time to get down. But in the context of the entire earth it's just a wee little bit on the outer part. Then there are some big pieces and little pieces. If you start moving these around some things got to give someplace else. That's why I thought we might start out with boundaries. What sort of boundaries and crust material are we all talking about? (Goes to overhead) Deb had suggested this as a great way to start.

Dr. Deb: That's right! We can talk about two different types of crust when we're talking about plate tectonics. We have the oceanic crust and then we have the continental crust as two major types and they differ considerably. So, when you're talking about continental plate interactions, an oceanic crust interactions with a continent, you really have to talk about the composition of these two because it makes better sense when you find out what these things do at plate boundaries. When we're talking about the oceanic crust we're talking mainly about the basalt composition. We're talking about a fairly dense layer. The density of the oceanic crust tends around 3.0 grams per centimeter cubed. That doesn't mean much now but when we take a look at the ocean crust that's going to make a difference. We're also talking about a fairly thin section of the crust, something that averages around 10 kilometers or about 6 miles in thickness. Then in comparison we can talk about the continental crust. The composition is granitic or primarily granite as opposed to the basalt in the ocean. It's relatively thick and you can give a measurement of about 35 km for the thickness or 22 miles. The other point to make is that it is fairly light compared to the oceanic crust. The oceanic crust being 3.0, the continental crust is 2.7 grams per centimeter cubed. When we talk about plate boundaries we'll talk about the density and then what happens when these two types of crust meet.

Dr. Bob: What's the density of the water?

Dr. Deb: Most of the high schools kids hopefully will say, "That depends on it's temperature." We'll say about 1.0.

Dr. Bob: Yeah, about 1.0. Then the combination is relatively interesting to figure out. If you had, for example, a flat line base and you calculate with the density, the very dense and the least dense material, the oceanic water base, then the thickness it's kind of interesting to figure out. Are they unstable, one with the other or do they kind of balance out in some cases? This is the critical thing, one of the critical things. What sort of boundaries are there? What happens?

Dr. Deb: Depending on what type of crust meets and which direction the crust is going will make a big difference. The first type of plate boundary we're calling a divergent boundary. This is essentially a pull apart zone or the plates are moving in opposite directions or away from each other. Remember these things are traveling on convection cells. Another point to make is this is not meant to instruct you on plate tectonics. We might go rather quickly so we want to alert you to the fact that if you need more information on plate tectonics please tune in to the adjunct next week, Monday where this will be dealt with in great detail. Your book has a chapter that gives you a brief overview, Chapter 3 on plate tectonics. We will cruise through this and don't be alarmed. These pictures and overheads that we're putting up will be available on the Web or actually are on the Web as we speak. They were put on there this afternoon. Don't try to draw the pictures just take the notes and download the pictures later.

Dr. Bob: The quick item is that it can happen, ocean ocean pull apart or continent continent pull apart. In Africa, for example in Tanganyika, the rift valleys, that's the only two types. The third potential, of course would be one oceanic plate and one continental plate. We don't see it. It just does not occur anywhere on earth. We're going to look for environmental events as a result of divergent in the second half of our show today as a result of ocean ocean or continent continent pull aparts.

Dr. Deb: Let's just give them an overview and then go through the types of boundaries. The second boundary we're going to talk about is a convergent boundary or a place where two plates are colliding or moving together. As Dr. Bob mentioned you can have different types of plate situations occurring there. You can have two ocean plates colliding, two continental plates colliding and you can have an ocean and a continent plate colliding. These give wrath to a variety of features.

Dr. Bob: As a matter of fact, these are some, with a play on words, movers and shakers with respect to the environmental concerns. These collision boundaries, just as the word might suspect, you pull apart but collision sounds a lot more violent. Indeed we'll find out in a very short bit that with respect to earthquakes and volcanoes these are some of the critical factors. There's one more possibility.

Dr. Deb: The third possibility comes when two plates slide past each other. They're moving in opposite directions relative to each other but not away from each other. Those are called transform faults or slide past motion as indicated with the arrows. That would be a top view as your looking down on it. These can occur in conjunction with these pull apart zones or areas where plate boundaries might be doing one thing but there might be zones in there where rocks are sliding past each other. We have this classic everybody is familiar with, the San Andreas fault for example. So we have a continent continent slide past or transform fault, the San Andreas, or we can have ocean ocean. A lot of people don't think about this but these can occur at the Mid-Atlantic Ridge which is a divergent zone. Pieces of the crust as they break and fracture can wind up sliding past each other.

Dr. Bob: Especially if you think about it in the ocean, such a real long rip and tear on a three dimensional nearly spherical surface, you can't just have a line. It's going to have little mini adjustments and that's what these transform faults are.

Dr. Deb: If you take your finger and you dimple a ping pong ball, what you're going to see is a curve. So you can't get a straight line and any attempt to make a straight line would result in fractures.

Dr. Bob: Next time when we have the adjunct we'll have a neat little paper model to put together and pull apart to demonstrate what these transform faults...but folks can really understand, they jump on this one. They know, even kids know, San Andreas, a big earthquake zone in California.

Ok, so those are the three boundary types. Let's go again to each one and give you an example. (Goes to overhead) We'll start up at the top...divergent boundary. Why do you have the little hump there Deb?

Dr. Deb: Well, it's pretty hot there. When things get hot things tend to rise. As things get cooler they tend to sink. As the plates are then moving away from that fissure eruption area they're going to tend to get denser and sag or sink. That's why the outside of the diagram is lower then that center portion where the fissure eruption area is.

Dr. Bob: Historically, by this I mean geologic history, that as the ocean basin gets very, very old, like a hundred and fifty million years old, it gets deeper and deeper. If that gets deeper the water gets into the basin off of the continental margin. So it drains off the continents. Then all of that assemblage of coastal environments on the geologic time scale, all those have to march with the waters edge. We talked about the Barrier Islands in North Carolina. They aren't eroding as erosion of mountains, they're moving and shifting in response to changes in sea level. Even though the Atlantic Ocean basin is very, very old, right now we have superimposed upon that some very, very active events like global warming. Warming of the water itself could cause the sea level to rise but there's a great buffering the whole ocean. If glaciers melt that water goes somewhere very rapidly geologically speaking. Much more rapidly then the plate movement. Plate movement is basically like watching your thumbnail grow. In one year that's the normal type of rate of movement of plates around the globe. We're going to find out in the second half that in Taiwan they're rate is about 4 times normal. No wonder there was some sort of an event. An example, we could talk about the Mid-Atlantic Rift. But there is one island that's well know, the land of fire and ice, far north, Iceland.

Dr. Deb: Which is on the Mid-Atlantic Ridge.

Dr. Bob: Therefore, it is an example, it's an excellent laboratory of that type of spreading center. What are the effects? Volcanism. Basaltic flows and earthquakes.

Dr. Deb: You get faulting.

Dr. Bob: When we talk about it the earthquakes are actually created by faults. Here's the next one that we had talked about, the continent continent. I point out that lest we suggest that the rift valley is only a continent situation...the rift valley can occur in the ocean floor too. There is a depression on the ocean floor in the Mid-Atlantic Rift. But on the continent this is what we see so very much of. The long narrow lakes. For example, Lake Baykal is long and narrow. Lake Tanganyika is long and narrow. The Red Sea is long and narrow. These areas where there is pulling apart. Madagascar and Africa pulled apart and there it is longer and narrow but deep so sea water has filled in in between.

Dr. Deb: As the crust starts to receive tension it starts to thin and then it starts to fracture and break. As it drops, and drops lower and lower, it'll eventually reach sea level and then will be inundated. The rift valley in Africa will undergo this at one point.

Dr. Bob: If we came back 10s of millions of years from now there would be two land masses with an ocean perhaps separating, just as Madagascar and Africa are separated today. The effect, there's some basalt flows. The footprints of early in the rift valley in Africa, the footprints of bipedal humanoids in that transition of the first hotfoot in the rift valley, but they're not real dangerous. The earthquakes are common, shallow but they're not overly a problem. Having said that...we're going to change gears. Convergent.

Dr. Deb: Again we're talking about plates that are moving towards each other and this is where the density is going to play a major factor in what happens. You've got the ocean crust that's meeting the continental crust. The continental crust being lighter then the ocean crust. The ocean crust being denser, it wants to sink below the continental crust. As it does this we have what's known as a subduction zone and a trench being formed. The ocean crust, subducts or sinks below the continental crust and as it does that it gets hotter and it starts to melt. That melted material then will rise, the magma will rise as it gets hot and gets less dense. It starts to rise and then you'll get volcanoes being formed.

Dr. Bob: What it can also pick up are elements out the continental crust. The essential one is silica. Silica is brought in from the continental crust and the magma changes composition.

Dr. Deb: It's no longer a quiet eruption.

Dr. Bob: The example would be the Cascades in the continental United States and west coast of South America, the Andes. The effects, whoa, there can be really strong earthquakes and very deep earthquakes.

Dr. Deb: That makes a lot of sense if you look at the picture because where is the contact occurring and you're going to see progressively deeper and deeper. If you graph these you can tell what type of zone you're on. That's a very good lab exercise.

Dr. Bob: The earthquake epicenter is directly on the surface above the focus or the location where slippage took place and as this continues to go down there's very good likelihood that the epicenter is going to be back behind the volcanoes away from the coast for those very, very deep earthquakes. The epicenters are very much inland. You really have to watch out for those volcanoes.

Dr. Deb: If you have volcanoes in this case you have mountain building processes going on. Another type of convergent boundary would be ocean to ocean. Here the situation is a little bit strange because you have two plates that are about the same density hitting each other. One sinks below the other one.

Dr. Bob: Eventually one will yield.

Dr. Deb: Again, you're going to have crustal material that's heating up, it's going to be mixing with sea water and picking up some other molecules. As it melts, it'll rise and you'll get these sea volcanoes being formed and as they get higher and higher and higher eventually they'll break the surface and you'll get what is known as an island arc.

Dr. Bob: An island arc, the volcanoes are not in a straight line but recall when you mentioned that taking your thumb and pressing it on a ping pong ball you get that arc. Where's there such a line of volcanic islands in the 50 United States that are an arc like this?

Dr. Deb: Most people are thinking Hawaii, but don't think that.

Dr. Bob: This is an arc.

Dr. Deb: Your thinking about Alaska here.

Dr. Bob: Right, the Aleutian Islands.

Dr. Deb: If you look at the westside of the Pacific you're looking at...

Dr. Bob: The Phillippines...Japan, the whole Indonesian archipelago is a huge volcanic mass but it's very complex. It doesn't look like a precise island arc. Another one exists between the tip of South America and the Antarctic Peninsula where the Pacific plate looks to be ramming full steam ahead into the south Atlantic. Which it is! There's a whole string of islands, Scotia arch (sp) geographically known that extends there. But the Aleutians are a great example. The effects...these rascals can explode. These are dangerous volcanoes. Lot of gas in there and we'll talk about that later. Earthquakes are no slouches either. Ask the people in Japan what comes most often, perhaps in the history of the past five centuries, is constant volcanic activity but when those earthquakes when they hit Tokyo and a number of other cities, it may not be the earthquake itself and the motion that creates the greatest damage...it's the fire afterwards. That cue is looks small but this V is very very large. These are all eruptive volcanic ones. This is still a pretty important cue for earthquakes.

Dr. Deb: The last of the convergent boundaries would be two continents colliding. An example that we have here for continental crust colliding would be India and then the Eurasian plate. As India moves northward into Eurasia we have the formation of Himalayan Mountains.

Dr. Bob: It keeps getting stacked up. Now whether it's stacks as shown here or stacks in the opposite way, India is colliding with Eurasia. It's a very interesting possibility. Look at how thick this becomes. This is the roof, the Himalayas, the roof of Mother Earth and yet on an absolute scale, on our peach or apple model, it's just a little bitsy bump. That again is very startling because we don't have a good picture of how big the earth really is.

Dr. Deb: You'll notice here that you don't see volcanoes here.

Dr. Bob: This is just a tremendous thickness, it's going to block out volcanoes. What it is going to do is magma is going to cool underneath. This is the molten material and becomes the root or the core of the mountain and it's only exposed hundreds of thousands, millions of years later if erosion gets down to it. Tens of millions of years later. Surprisingly fast because if we went on a trip to Yosemite we'd get down into a core granite layer. If we went to Idaho we'd get down into an exposed core granite area from a very ancient type of plate plate boundary where its convergent continental. The effects...quakes and faulting, the faults lead to the quakes. You wouldn't expect, "Oh, does this mean that in every single case were this ever to happen in geologic history there's no volcanic activity, only minor, only a little vein that maybe escaped out of the magma chamber and then cooled before it even came to the surface.

Dr. Deb: The big thing here is the mountain building or the crustal thickening. That you want to remember for continent to continent.

Dr. Bob: Eventually it's going to die out. We'll talk about this next week. It is a system that can't go on forever. None of these boundaries can go on forever. They're just going to die out. What we have here is a single example...continent continent transform fault. Notice the big arrows here. This is known as a right lateral fault because no matter which side you stand on, the other side appears to be going to the right. In conclusion, right boundaries are important. The importance because of volcanoes and earthquakes and also mountain ranges. That sets up a whole sequence of events for the second half of tonights show where we'll talk about earthquakes and volcanoes and the environmental results of plate tectonics. Stay tuned, we'll take a 10 minute break here and we'll be back shortly.

BREAK

Dr. Bob: Greetings back again. Just to reiterate, a few people had trouble getting online and we surely hope that those three sites were able to get on line. There will be a quiz that will be on the Web site tomorrow morning. We'll try that system where you can answer it on the Web site, do it electronically. You'll always have the ability to send a hard copy in especially if you want to do some extra sketches to amplify your answer. I always urge you to keep a copy in your own possession just in case something gets misplaced in the mail. The exploratory's this coming weekend. You have to let Tom know what your choices are, will you be there Friday at noon at the Holiday Inn in Parkersburg at the intersection of Route 50 and the Interstate. We'll be out all Friday. We'll come back and we have rooms reserved, that's why we need to know that information by Wednesday. Tom will correct me if I'm wrong on that, but we need to know cause we have those rooms reserved. Some of the folks may want to problems they have and whatever their schedules are they can meet us, we will come back again, loop in through the Holiday Inn at noon on Saturday and pick up a second crew. Finish the Saturday afternoon with everyone together then we split off and the ones that came on Friday they retreat home and the ones that came on Saturday, we stay there Saturday again. We have a night session. Both nights it's the same session and then we'll run until about Sunday at 1 o'clock or so. Then all of us will depart. This is the first exploratory. We need to know your commitment please because we have blocks of rooms set aside. There is also on our Web site with revised dates on the syllabus and a few of the activities. There will be quizzes from now on. Tomorrow morning there will be four or five questions, you can talk amongst yourselves but you each have to answer the quiz in your own words and in your own way. Books, we've had a pleasant surprise, it's one of the reasons that we're a bit fluid on the exploratory is because we had so many people and it's great. It's one of those pleasant problems to have to resolve. We have over 100 people in sites around the state that are participating. We've had to reorder the textbooks again, but they should be out and to you and if you want to know the reading we are reading in the first five chapters. The end of today's discussion we would have covered everything inclusive chapters 1 through 5. That's the reading that you make up. There's lots of pictures. It's a hundred and fifty pages but a tremendous number of cartoons, diagrams, pictures and tables that help break up the reading. That's what textbooks do so well. They share with you in multiple colors and in descriptive ways some of these more complex ideas in a capsulated form.

(Goes to overhead) I'll remind you again that we started out with the plate tectonics and went to the break and come then with "Ghoulies and ghosties and long leggity beasties and things that go bump in the night, good lord deliver us." Now we'll talk about earthquakes and volcanoes. There's one thing we didn't talk about in the context of the plate boundaries. We didn't talk about a unique situation that is not a boundary of plates, that's why it didn't fit, but rather as a circumstance of uniqueness with the engine that drives the plates, the hot spots. A hot spot is a situation where a convection cell is pumping magma up. Magma is hot, it's lower density, therefore it's going to want to rise. What happens in a hot spot is that the plate, I'll just use one direction, is moving over the hot spot. With the magma rising it comes up through the plate and it creates then a volcanic cone. That cone has an opportunity to build through multiple eruptions, but the hot spot is moving. The hot spot doesn't move but it appears to in the context that the volcano starts to get spread out like so many chocolate kisses on this plate of lithosphere that's moving over it because the plate is moving over the hot spot there's going to be episodic construction of volcanic cones on the plates surface. It this is an oceanic plate and the water then will be the cover of that plate sometimes that volcano will break the surface. If it does then erosive powers storms in the ocean are going to start creating the potential for planing off the top of that volcano. If this is warm near equatorial water then there's the potential for reef structure. Coral reefs we call it, although much of the rock material is algae and the coral reef material might grow up around this volcano. Just as we had mentioned in the first part of the show, this is a hot spot, magma is coming up, there's higher temperature, it's less dense. As it moves off the hot spot the plate will sink. Along with the plate goes the volcanic cone. Sometimes the volcanic cones still stays poked a head above water. Sometimes the coral reef keeps pace with the sinking volcanic cone. But in the mid 1800s when Darwin went on his journeys he said, "You know, we're out here in the Pacific," this was in the 1840s, "my guess is that these coral atolls, these fringing type circular atolls really are based on volcanic cones because we're out in the middle of the ocean. It's really deep water. We can't even plumb the depths to know the true depth. We don't have enough rope on board in order to throw it overboard to see how deep the water really is." He said, "My guess is that there are volcanoes beneath these coral reefs and that the volcanoes had supported the coral reefs but the volcanoes had now sunk out of sight." Now, volcanoes and hot spots in the ocean form islands and these islands tend to be in one or more generally parallel lines. The example is Hawaii. There are at least two generally parallel lines that you can use to describe the presence of the Hawaiian island chain. However, if you look at the entire Pacific ocean and you look at the Hawaiian and you want to know more about plate tectonics we'll talk about going all the way out to the little island of Midway. Those WWII buffs in the audience will recall the importance of the Battle of Midway. That's in the same chain except that there are very, very fewer islands that stick out above the water because this is so old. It got cooler, more dense, sunk out of sight. On the ocean floor we can still find volcanic cones. Even more we'll talk about the possibility that these shift in direction so that there are many more islands like this in the Pacific ocean, especially as compared and contrasted to the Atlantic ocean situation.

Let's talk now about earthquakes and start out our discussion in the chapters in sequence. I will most often just abbreviate and talk about quakes. The general structure of a earthquake and the reason it causes damage...remember we're looking at the environmental concerns...and over the past four weeks, in order, there was a massive earthquake in Turkey. Then one in Greece, then one in Taiwan. After each of these major events there have been thousands of after shocks. The main quake occurs and then after shocks. Some of them are very violent in and of their own right. Buildings or structures that had been weakened may fall. There was an after shock yesterday in Taiwan, a 6.5 on the Richter scale and three people perished because of additional structural weaknesses. As you can well imagine, you hear of the teams of rescuers going out into these structures that have collapsed when there is constant after shocks. There may be an after shock every minute when your working there. Think of how that plays on the minds of those poor folks who have had to survive the first major shake and then try to live through that and to create the rescue opportunities when they are constantly being shaken by these after shocks. You'll usually find that most of these folks, once the buildings have been shaken, they'll want to sleep outside, which is fine when it's summer. what happens when it's winter? The fact that they have been deprived of their homes, their structures have been weakened and even though the home may stand it's declared unsafe or the worst case scenario has happened many times in earthquakes in history, that fires have begun after the earthquakes. The 1906 earthquake, the greatest damage was done by fire as a result of broken gas lines. These earthquakes have a great series of problems associated with them. What causes earthquakes? Where does it really come from? The real cause is a break. A break in the rocks. We call a break in the rocks a fault. The rock has been put under stress. The stress may be pushing or compaction or pulling or side by side as if tearing. The stress is the force applied. That's the force. Then, eventually the forces are too great and the material, the earth material can no longer withstand those forces, the strain is the deformation. Some types of forces, not major workers in this event in nature, is just a compression. Like taking a press and putting a watermelon in it and squeeze it. Eventually the watermelon is going to yield because it doesn't have the strength. David Letterman used to do this, take a can of pork and beans and put it standing upright in the press and then pressure. The pressure is ;just top to bottom and eventually the can, even filled with the material inside, can no longer take that pressure, it will yield. Yielding is the strain, the deformation. It may break, it may almost explode or it may fracture and tear. In geology in the earth materials we are talking about things that take place excruciatingly slow in the context of human life span. In some cases earth materials put under stress will not break but initially just bend and bend and bend. It's buried so deeply it acts in an almost plastic fashion. There are additional materials then, additional features that we call folds. Like you take this sheet of paper. (Demonstrates with a sheet of paper) These different layers are rock. I can fold it. This type of fold when the pressure is released will not spring back into shape. It's an anticline. This is a syncline. Neither anticlines or synclines that describe folds create the earthquakes.

(Technical difficulty here joined in progress) Two geophysicists named after one Richter scale gives numbers 1 through 10. Perhaps some of the largest ever recorded were just under nine. This tries to describe both the amount of energy and the potential for the amount of movement. You may see some varying numbers depending which way they are trying to describe the energy released in the Richter scale of earthquakes. Then some newspapers and other publications try to put on the material as to how it was felt, how it was observed by people. Mercalli scale, roman numerals 1 through 12. The terminology for those roman numerals is somewhat archaic. Chimneys fall, people run out of the house. Not many folks have chimneys anymore but this was the type of scale that helped to describe what people sensed as they lived through these earthquakes. What about the transmission of the energy. The transmission of the energy is what creates the shaking and the problems on the surface. There are body waves, they move very rapidly through the earth. The ones that move most rapidly as the P waves. They're push-pull waves. Here's a recent diagram that I provided in a test and it's a slinky. This slinky started out with the uniform positioning of all the wrinkles in the slinky but it starts out with a body wave type motion in a P wave and there is extension here but compression there and then the compression bounces back and it causes the material ahead of it to compress. The wave just continues on as in these four pictures. This is in a solid material, in a spring. It also works in the context of rock. The body wave sends motion straight. The ;motion of the particles is back and forth. They collide and bounce back. This wave can also pass through water. The example, throw a stone into a quiet pond and you will see the ripples move out. That's the same type of phenomenon where the impact of the stone in the water is created and instantaneous compression, it rarefies, it goes out, but as that rarification goes out it squeezes the particles at the edge and ripples move out. Eventually, the water quiets down. The energy has been absorbed by the system. The primary wave moves through solids, as with the slinky or just take a table and pound the top of the table. Do you feel a vibration if your touching the other end of the table? The answer is yes. That vibration has been transmitted throughout the solid. That's an earthquake felt a distance away from the actual greatest energy has been released. P waves also travel through gases, rather trivially you say with respect to the earth and it's true but in the sound system that's why we have sound. Our ears pick up those vibrations and retranslate them, not only into sound but also so we can discriminate in voice and tone. It's a magnificent piece of human engineering if you will of the human body for the P waves. The other wave that is a body wave is the S wave. It's a shear wave. Only solids have shear capabilities. The shearing motion is up and down and in the plane perpendicular. If I generate the wave out to you as you view me I'm doing it fanning out and shearing the particles. In a solid that happens as the material moves. An analogy take a rope, attach the rope to a doorknob and then with a sharp movement move your hand vertically downward. Up and down. That energy is transmitted along the rope and it's moving perpendicular to the path of movement of the wave itself. The wave will pass from you to the doorknob but the rope is going to go up and down as the energy is transmitted towards the doorknob. Those are the body waves, P and S waves. These are often called the primary waves because they get there first and if you want another term it's a push-pull wave like the slinky and these are the secondary, they get there second. We can measure when they arrive and what energy they bring to bear. Then there are surface waves. A variety of motions. Some of them even roll. But this is the type of wave when the wave is propagated in this direction, some of them roll like this. You've often seen attempts in Hollywood of portraying an earthquake. People saying the land actually rolled beneath my feet. That's because of the surface waves not the body waves. The surface waves travel very, very slowly and have rather unusual movements. Like this one moves backwards even in a counter clockwise direction at times overall yet the energy is being transmitted in the direction shown by the large arrow outside of this rather cluttered circle.

Now, the surface waves are a real problem. What if you are living in a building that is build on bedrock, your friend next door is living in a building that is built on sand and gravel. Two blocks down your cousin is living in a building built on mud. Further on down the line a good friend is living in a building built on fill. That is the picture of San Francisco Bay. In the World Series Earthquake, also the Loma Prieta (sp) earthquake as it was known by the scientists. The energy that is transmitted through the bedrock can go quite some distance, especially the body waves. The surface waves do not have a great impact on solid hard firm well cemented bedrock. Sands and gravel on the other hand deaden the energy of body waves but sands and gravels will scinter (sp) down and shake. You ever open a box of cereal and wondered where did the cereal go. Especially some of those round corn puff cereals. They're all scintered down and there's a little warning, Package was full when we put it together and sealed but it may have settled as a result of shipping. That's what happens in these situations in sand and gravel. Mud, you've all kinds of problems. Mud may slip and slide, you've seen some buildings in the Taiwan situation where they just seem to sag over. They just must have slowly slid over. As a matter there's a picture of an earthquake damage in Niigata, Japan where the number of apartment buildings, two or three of them just sagged over and slid down because the clay underneath the building structure was grain to grain boundary when they built the five or six story building but the earthquake shaking caused the grain and grain boundaries to be isolated and therefore the mud flowed. It's called thixotropic clay. The process is called liquefaction. As the word suggests, liquefaction, that's not good. I recall very vividly the newsreels of the day in Niigata, Japan, where owners were walking wheelbarrows up and down the outside of the building to get into their third, fourth, and fifth floor apartments because one of the buildings was totally on its side. No one was killed, it just sagged over and settled down because the clay underneath went to liquid. Two buildings away the building is still standing and one of the buildings in between is leaning at a precarious angle. Obviously it's going to have to be replaced. As a matter of fact maybe all buildings are going to be damaged beyond repair. Who's going to live in a building knowing that the one next door just tipped over and sagged over the last time they had a major earthquake. Where are these earthquakes? The fill material is not good because that really is going to settle. Where are the locations of earthquakes? As we described in the first half of the show there are quakes along plate boundaries. Sometimes more violent then others especially in convergent plate boundaries or the transform fault situation and it's especially a danger in any situation where we say that the rocks on either of the fault are locked. If you put your hands together and you press and push and push and finally the friction is overcome and the forces are overcome. It had been locked in position for many, many decades. The energy wasn't bled off in numerous small earthquakes, rather the energy occurred in a sharp break or fault with major displacement and as a result there was a great deal of energy. This great deal of energy caused an enormous amount of damage on the surface. One earthquake that comes to mind is the North Ridge earthquake in Los Angeles. In fairly reasonably close time, in January a few years back. In that earthquake it was called a blind thrust. What happened is that the forces were moving to the north and the fault zone is in the plane of my hands now and the fault zone angled up. The mountain actually rose at least 18 inches in that one event, in that one release of energy. We call it blind because the fault doesn't come out on the surface. The North Ridge event, the forces were tremendously strong and the fault was beneath the surface but it did not come up to the surface. The forces are coming in here from the right, this upper block shifted up and yet the fault never came to the surface but this mountain went up 18 inches in that one event. Think of the forces that it would take to take this entire mountain and move it 18 inches vertically yet in the United States, especially in California since 1906, long term construction codes and engineering codes initially begun by the Japanese and perfected by both the Japanese and American engineers, is an attempt to not only prevent new buildings from being susceptible to damage but also to provide mechanisms for retrofitting old buildings. Now sometimes we definitely, in every instance, we want those buildings to move. We don't want them to be perfectly rigid. It's a perfectly rigid building in the face of an earthquake it's at great risk. The structural units are not going to last. Build a house of cards and then just push it on its side. That's no fair, we built the house of cards and I took all this time to build a vertical structure to make sure that I had created vertical support. Yeah, that's fine but an earthquake may move vertically but also horizontally in several directions, east, west, north, south or some other sets of directions. You say, "Well that's different, my house of cards can't stand that. You just touch very gently and the whole thing will collapse no matter how many stories I've built up very carefully." If you allow me to take a piece of tape and tape the cards together in the angles then it's going to last. If you're going to live in that area would you take angle irons and attach your 8 foot bookshelf to the wall, the 2 x 4s and the structural part of the house so that if an earthquake did hit the whole bookshelf doesn't come at you, some of the books may. Or you may even have some sort of design, it may not look great, but you may have a design to keep the books on the top of that 8 foot book shelf from coming out at you if your walking past that bookshelf or sleeping or resting nearby when the earthquake hits. There are ways to try to retrofit your house. It's not going to look pretty but your gonna want to strap your hot water heater and furnace and other utilities to the foundation, the 2 x 4s, 4 x 4s or whatever structural foundation. You're going to attach them in the basement so they don't tip over. If they do tip over, especially if their gas line fed then you've got the problem of fire. There are ways in which we take big buildings and we actually excavate and them we put large rubber grommets, like huge washers underneath and let those washers absorb the energy that will be transmitted from body waves through the bedrock into the building or surface waves through the unconsolidated materials and into the building. Another way in which their engineering things is take a tall building and put a very large weight suspended from cables in that building. If an earthquake does come then try to transmit the building motion and let that moveable weight and mass on cables respond to the rest of the structure and in effect protect the rest of the structure because it moved very readily. It was a mechanism, an engineered mechanism that helped the rest of the building survive. Earthquakes occur in California along the San Andreas. (Goes to overhead) Look at this particular drawing that I did on a test recently. It was perhaps three of the greatest earthquake intensities ever to hit the United States in historic time, in European historic time. The location was New Madrid, Missouri. Here's Memphis, here's St. Louis, Carbondale, Illinois, Paducah, Kentucky. Cincinnati's up here, Chicago is up here. Little Rock, Arkansas. This intensity, three earthquakes in December of 1811 into January of 1812 that perhaps on the Richter scale were 8 and above. An enormous amount of energy. A lake was formed because of the cutoff of the Mississippi River. It forced part of the Mississippi River and the sands and gravels to be shifted around, movement and the pressure of ground water caused sand to move and shift and as a result that whole sequence was dramatically changed. It hasn't happened since, it's a very infrequent situation. In 1886 an earthquake in Charleston, South Caroline. In Charleston, South Carolina the energy was felt in Minneapolis. Scaffolding fell around the White House. It was felt in Toronto, why? Because in the eastern United States the bedrock, the body waves can go through fairly continuous rock units without many faults breaking it up. The energy that is released in the San Andreas gets cut off in those broken rocks in the fault zone of the transform fault. It doesn't get across as readily and with the strength into Utah and Colorado. In certain directions earthquakes and any movement can cause major events. The mechanisms that we use to detect is a seismograph. The seismograph we have here in the geology building in White Hall in Morgantown was running when hurricane Hugo slammed on shore in South Carolina a few years back. That energy of the hurricane, the atmospheric pressure, caused our seismograph to just shake and shudder in Morgantown, West Virginia. The earthquake in Mexico City in 1985 caused water to slosh in wells in Denver, Colorado as that energy was transmitted through the earth. There is a straight line shot from Mexico up to Colorado without major faults dampening off that energy. The stories of these types of earthquakes and the results are incredible.

Another one of the great problems of earthquakes is that if the earthquake occurs out at sea and there's movement and the bottom drops of the sea floor, water's going to move. When water moves that catastrophically it creates a seismic sea wave or a tsunami. It's a Japanese word, it races with incredible speed through the ocean but the amplitude of the wave and the water is just a foot or so. If all that energy come to focus in an enclosed bay in Hawaii or Japan, from an earthquake in Alaska, the resulting wave may be forty or fifty feet high. Tsunami is also called a seismic sea wave but it is not a tidal wave that you'll hear on the news or read in the press. Tides are the earth, moon, sun system. Seismic sea waves generated by earthquakes occasionally even volcanoes should be called by their rightful best name of Tsunami. These's are devastating. Tens of thousands of people have died as a result of tsunami being generated by earthquakes. Those earthquakes occur and the tsunami occur so rapidly that there's not enough time to warn the people if the earthquake is taken place just off shore and it come's onto the island, say, of Japan. If the earthquake takes in Alaska then we have time to warn people in Hawaii and Japan. In Japan, especially, they build sea walls in the event, in certain towns and communities, to prevent tsunami from engulfing the town and destroying homes and causing untold loss of life. Whole fishing villages disappear. One occurred just a few years ago tragically in Japan as a result of a earthquake just off shore then the sea floor dropped. There are a couple of other terms that we should really know here, one is below the earth's surface there's a focus. That's where the break took place and whatever the fault looked like may be we're going to show another fault like this. This is the focus. The energy, the potential for great damage here on the surface, the epicenter. We can determine the epicenter by triangulating in from different recording stations around the reasonable vicinity and find out how much energy arrived at the recording stations, what time it took the energy to arrive and how it affected and how we can locate the epicenter where the greatest damage may well have been done.

The last comment is, what happens in the case off the northwest coast of the United States? There is a subduction zone. You don't hear about Seattle having major earthquakes in historic time or Tacoma, Washington. But, when we drill down into the sediments look at what we find here. These dark black lines on this drawing that are horizontal are called coal or organic material and they provide carbon 14 dates. This one was about 745 years ago. This one 500 years ago. The one at the top is not disturbed and that's the current one and has been accumulating for the past 240 years. Look at the displacement. The displacement here between that bed and that bed that displacement between that bed and this bed, this lower one has been moved twice. It's been moved the amount here and then an amount earlier so that there is an episodic sequence. In the past 745 years there have been two events and then there was another one, younger then 500 years but older then 240 years. There's an event here and here. What does that suggest about today's current events? This one took place between 745 and 500, that's 245, this one between 250 and 240, that's 260, this hasn't moved for 240 years. We might expect in this particular location that the stresses and the forces are building up and just because no one was here to record it that long ago doesn't mean it can't occur again. The recurrence interval. The time between the earthquakes.

Earthquakes are around plate boundaries. So too are volcanoes. The ring of fire is something that lot's of folks have heard about. A ring of volcanoes around the plate boundaries, especially the Pacific ocean. We also have hot spot volcanoes to deal with. In the United States we have three special areas of hot spot volcanoes. The one of course is Hawaii and it's the islands. Then there are two others that are well known and one that you probably had not heard of in the United States proper. One is a national park, the first national park. It sits over a magma chamber. That magma chamber is still active. It provides a great deal of heat to the rock material so that when ground water seeps it gets heated and super heated. The groundwater above is the cap to the super heated water. Until that water has built up such great pressure and steam that it blows the water out. What national park would you go to? Yellowstone National Park to see "Old Faithful" geyser. Turns out that it's not old faithful anymore. It's taking longer and longer for the eruption of the geyser as compared to 30 years ago or so when I first visited it. The reason. As all these tourists come in, everybody would like to buy a slushy or have some pop or a cool glass of water in the summer months, right! Where does that water come from? Not only do they drink all that water but they also expect facilities because they're only renting all that water or the pop or the slushy for awhile and they'd like flush away the waste material. Where does all that water have to come from? The ground water, so in the past 50 years we have robbed the ground water supply that used to serve as the cap to become super heated to erupt and then fall back on the land to seep down in until it erupted again. We've begun to recreate an environment at that location in Yellowstone National Park. Another location is Long Crater along the border of California and Nevada. Mammoth Ski Area is along there. Many people don't recognize that one. It is a situation a lot like Yellowstone National Park and a third one is outside of Santa Fe, New Mexico. If you look a the satellite imagery map of New Mexico there's this huge circular blob on the imprint of just the vegetation, just the surface. You're not looking at a geologic map. Of course when you look at the geologic map this is a huge, huge area. It's a massive volcano. It's called Valles or the Jemez Mountains north and west of Santa Fe. They were in the news recently because there is a single owner to an important valley and that owner has ranching interests in Texas. Each spring they would send cattle up to this valley because it's a high elevation and the grass literally grows waist high. It is unbelievable. On a field trip we were just watching hundreds and hundreds of elk in this huge grassland prairie in the center of a caldera of a volcano. We had just come from a hot spring where hot waters were bringing up material from the magma down below. Then the hot spring had dissolved some limestone and the limestone was precipitating out as the temperature of the spring dropped. The Jemez Mountains outside of Santa Fe, New Mexico are absolutely spectacular. The United States government has an opportunity to buy that property, lock stock and all elk present for the perpetuity for the American people. It's a huge acreage, 90,000 acres or something like that. It's not trivial. Hopefully we'll find that money and preserve it forever. It's just absolutely beautiful. It's a hot spot, there are volcanoes. We also know there are volcanoes in the Cascades. Mount St. Helens, that erupted in 1980. I have kids in class that weren't born yet and their college students. We have this time frame of relevance. Volcanoes are that much of a problem in the United States, are they? Mount St. Helens, yes, but Mount Rainier is also a volcano. Mount Hood, Mount Baker, Crater Lake, the caldera or central portion collapsed back in as magma drained down. There's a whole line of volcanoes, not a straight line but a sequence of volcanoes we call the Cascades. Lassen Peak in California erupted in the late teens of this century. Everything was quiet until 1980 but Mount St. Helens got our attention. It hasn't held our attention because in the adjacent 48 states we don't have that many of those type of events to look.

Going back to Yellowstone National Park on the overhead. This big dark arrow shows the direction of plate movement. The plate is slowly moving in this direction. There have been three major events. One of them was 2 million years ago. The next one was 1.3 million years ago. The last one was 600,000 years ago. What does this suggest? One, that it happens more than once. Two, that there's an interval there that in the next 10s of thousands of years, hundred thousand years there could be another eruption. The largest of these released material in Yellowstone National Park released 1,000 times as much material as did Mount St. Helens. These in Yellowstone are called lava domes. They're the most dangerous of all. There are three types of volcanoes. The shield volcanoes, that's Hawaii. As far as danger to humans, no. It's a flow of basalt. It's material that comes out rather slowly and you can outrun it. If a buildings in the way you have a problem. Stratovolcano, these are a problem, Mount St. Helens and the Cascades, Fujiyama, lot's of ones. These are a problem, they are intermediate and they can blast a lot of gas is emitted. Then the final one a lava dome. These are the most dangerous of all. Like Yellowstone, Long Valle Crater and the Jemez Mountains. Volcanoes can directly affect us through gases and explosion and debris in the air. Indirectly if there's a glacier on top the glacier melts. The melt water picks up all the debris, it floods down the valley. That's what happened in 1985 and over 30,000 people perished in the country of Columbia. The same type of deposit occurred several centuries off of Mount Rainier. Some people in the outskirts of Tacoma Washington are living on deposits that flowed down the mountainside.

Read those chapters 5 and 6, specifically for tonights discussion on earthquakes and volcanoes. We'll pick up again. We always review a little bit when we return two weeks from tonight for the regular showing. The adjunct next week will be on plate tectonics. Until then watch the newspaper for special events, take care, see you soon.

WVGES Education Specialist, Tom Repine (repine@wvgs.wvnet.edu)

Page last revised: October 1999

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