Faces of Earth - Assembling America

Seattle Washington it's considered one of the great places to live in America vibrant full of energy life for the residents here just rolls along in a predictable fashion yet things are rarely as they appear from the Pacific Northwest to the shores of the Atlantic seaboard the breadth and scope of the North American continent is like no other place on earth the land we see today was shaped over hundreds of millions of years look up look around look deep below in this episode we take a trip across America from the Pacific to the East Coast exploring many of its geologic wonders and how they were formed on the face of Earth Mount Rainier erupts and threatens to make Seattle a modern-day version of ancient Pompeii this is the nightmare scenario of what happens if we build our cities in nature's way the thing is we do it all the time so it's not a matter of if but when nature and humans will collide we like to live close to water surrounded by natural beauty the Pacific Northwest provides that type of living but it also is a microcosm of the dilemma the realities earth can force us to face the America we know has been evolving for hundreds of millions of years it has never been static nor will it be in the future Earth's outer crust is like a fluid mosaic of many pieces breaking apart over time colliding and grinding against each other in the Pacific Northwest where the Pacific Ocean meets the American Shore the fundamental tectonic forces that shape all continents are locked in an epic struggle what's special about this place is that we're standing basically fifty to sixty kilometers away from the edge of the North American continent and what happens beyond that edge is that you have an oceanic plate that is subducting or basically plunging beneath the North American continent plate and causes volcanoes east of where we're standing the Washington coast is part of a subduction zone where the ocean's crust dives beneath the continental crust and into the hot metal of the planet here the tiny Juan de Fuca plate is sandwiched between two titans the hammer of the Giant Pacific plate and the anvil of the North American plate leaving it nowhere to go except down and under if you continue further west about 600 kilometers what you reach is the point of food coverage and this is basically the end of the Juan de Fuca plate at a Ridge what you have is a divergence you basically have two plates that are moving away from one another by pulling apart two plates like this you release pressure and what happens is you're melting material at the same time and you're generating some new crust there as the new crust expands outwards the Juan de Fuca plate slides under the coastline of the Pacific Northwest with profound geologic consequences when ocean crust is forced back into the mantle a lot of water is carried with it when the water reaches the superheated layers below it boils and starts to rise back toward the surface looking for an escape as it moves upward if it reaches a particularly viscous area the heated water and other gases build up immense pressure the result is catastrophic some of the things that makes these Latinos very explosive is the fact that there's a lot of water coming out with the Magma's most kinds of volcanoes and other tectonic settings don't do that the Olympic Peninsula of Washington is the only place on earth where scientists can easily work so close to an active subduction zone jeff Abers Stefan Rondon a and Ken Krieger are part of a research team that is installing the infrastructure to conduct long-term monitoring of this complex system we are at a very basic level trying to understand things like why do Valle knose appear where they appear we're trying to understand where it is that in a long geologic context material goes or very close the flanks of Mount Rainier so we're reaching the point where the deeper parts that has become very hot and fluids become mobile one of the things which I understand is that transition how does the fluid make it down this deep Cascades are especially interesting in this regard the chain of 13 major volcanoes that form the Cascade Range extend from the Canadian border to Northern California in a way they are pressure valves for what happens deep below these volcanoes are the exhaust from the great recycling engine of Earth the consumption of oceanic crust as it's absorbed back into the metal these scientists are placing an array of instruments that will extend from the Columbia River to just east of Mount Ranier power they hope to get a clearer look along this length of the subduction zone and eventually create a high-resolution image right so I think we're good what we're doing is we're installing some seismometers the instruments are really sensitive they record not only earthquakes that happen here but earthquakes that happen in Japan we can record earthquakes that happen in Mexico in South America something at all we then analyze these data to obtain images down to about 200 kilometers all these ties makuey --vs illuminate the region over which we're standing right now from below the seismic field equipment is designed to operate for years providing data to create images similar to this one this picture outlines the Juan de Fuca plate subducting into the subsurface beneath the North American plate when two tectonic plates collide major geologic events are bound to occur the Pacific Northwest is not only known for its volcanism but also for earthquakes an high-tech barly operation earthquakes happen when energy is released due to rocks slipping past each other deep underground like when one tectonic plate overrides another if it happens suddenly the resulting seismic waves caused the ground to shake and roll and can inflict great damage on the surface On February 28 2001 north quake of this type measuring six point eight on the Richter scale rocked the Seattle Olympia area no one has the Nisqually quake its source was over 37 miles deep and produced shockwaves that radiated out in all directions like ripples on a pond this is what we usually envision when we think of movement deep in earth but scientists are now learning about a new type of underground event imagine an earthquake of the same magnitude as the Nisqually quake but you can't feel it yep was that 10 years ago nobody even drunked about this and now we're seeing it everywhere and so it's a it's a phenomenon that we would very much like to understand this phenomenon is known as episodic tremor and slip or ETS for short the same amount of slip you get during these megathrust earthquakes was occurring in these events that take two to three weeks to happen but they add up to a magnitude six and a half or so earthquake so in effect we have magnitude six and a half earthquakes every fourteen months but they occur so slowly they're not they're not felt in there's of course no damage scientists were surprised when they realized how much movement was taking place underground and how much stress was being relieved by these recurring mini quakes this network will eventually have 60 to seismometers in place over the next several years they will provide a new more complete picture of subduction zones and the role water plays deep in earth it will also provide us with a greater understanding of future events like ETS in this geologically active area of earth right in our backyard America is like a quilt of interlocking earth systems sewn together over time this becomes abundantly clear as we move eastward and the landscape changes but the cause is often a mystery Esther's Widow here just a few hundred miles east of Mount Ranier it's easy to see something dramatic happened scientists believe it had to do with flowing water just one problem there's not a river in sight you from up high the world below looks dreamy with not much happening but looks can be deceiving these are the channeled scablands of Eastern Washington State in the mid-1800s the first settlers gave them the name scablands to them it looked as if the skin of the earth had been mysteriously ripped away in great gashes leaving wounds only partially healed with giant black scabs Vic Baker from the University of Arizona has been studying this area for over 30 years standing here in the middle of scab land area it's it's very difficult to get an impression of the scale what you can't see from the ground is that this kind of topography extends over widths of 1020 miles in all the scablands comprise over 13,000 square miles much of it remote Esther's Widow the best way to study it is by air so Baker is brought within to ultralight aircraft both mounted with cameras to record images of this massive tortured landscape so what caused this remarkable typography for generations geologists were stumped and struggled to understand what they saw using their limited knowledge of its processes ok well the pictures look good but maybe if you tried from a little higher elevation gyeo scientists do know that about 20,000 years ago great ice sheets covered much of this part of North America this was the most recent glacial advance of our current ice age but around 18,000 years ago global temperatures began to rise and the ice sheets some of them several miles thick began to melt as the glaciers were retreating there was a tremendous amount of water that was released and the result was that you had these giant lakes surrounding the ice one of these lakes we know as Lake Missoula it formed behind an ice dam created when the lobe of the retreating glacier blocked the Clark Fork River in what is now Idaho that Lake held about 500 cubic miles of water and had a depth of 2,000 feet at the ice dam so the pressure of all of that water much more than behind any man-made dam meant that the situation was set up for immense catastrophic flood one day with a sound that can only be imagined ice dam let go and the Lake Missoula mega flood surged toward Washington State 150 miles away the hill I'm standing on is about a hundred and fifty feet high so the flood water was at this point about a hundred fifty feet deep and over behind me toward the Palouse River deeper than that 100 miles later the wall of water rushed past this point at around 50 miles an hour that would have in it blocks of ice there would be boulders animals trees absolutely frightening sight of immense proportions the flood would have been an inspiring sight to fly over the scablands mega flood floated a rate of 388 cubic feet per second that's ten times the flow of all the rivers of the world today combined while the echo of that thunderous wall of water has long since faded away from the vantage point of an ultra light one can clearly see its effect to this day as the ice sheets from the last glaciation retreated lake Missoula was not the only great body of water left behind another was Lake Bonneville but in contrast Lake Bonneville located in present-day Utah didn't disappear in the massive rush of a flood but shrank as the region became drier over the last sixteen thousand years as it did so the water already rich in minerals washing in from the Wasatch Mountains became concentrated and hyper saline the last remnants of Lake Bonneville is the Great Salt Lake situated in the Utah desert the Great Salt Lake is nestled in the area known as the Great Basin the landscape of the Great Basin is defined by north-south mountain ranges separated by wide flat valley floors it occupies 200,000 square miles covering much of Nevada and Utah the mountain ranges that define the Great Basin to the east and west are moving away from each other at a fairly high rate of speed in geologic terms doubling their distance over the last 40 million years this has resulted in the locations of Reno Nevada and Salt Lake City moving apart 50 miles in just the last eight million years alone as the lower crust was heated and stretched it thinned causing the crust under the Great Basin to become some of the thinnest in the world the extensive fracturing and faulting from this tectonic activity also allowed superheated waters to move minerals and metals in the crust forming large deposits of gold silver copper and lead the metals attracted people to this part of America seeking their fortune in the austere beauty of this region travelling east again the same type of forces that pulled apart the basin and range also sculpted the majestic Teton Range in Jackson Hole Wyoming just to the north of the Teton Range lies Yellowstone National Park perhaps the most notable example of what happens when the heat of deep earth comes close to Earth's surface Yellowstone National Park is not only a unique and exotic ecosystem but it is also home to a dramatic window into many of Earth's processes 60% of the geothermal fissures and 80 percent of Earth's geysers including Old Faithful lie within the borders of the part but two million years ago this landscape looked very different then three major volcanic eruptions of staggering proportions one as recent as six hundred thousand years ago created the site of the world's first national park Yellowstone no one knows how long the most recent of these explosions lasted weeks possibly months but in that short timeframe two mountain ranges the size of the Tetons were annihilated dr. Bob Smith a geophysicist at the University of Utah is one of the world's foremost authorities on the geology of Yellowstone we're on the North flank of mount washburn in Yellowstone National Park but most folks visiting the park don't realize is that this high plateau is out of norm we should expect to see large mountain ranges here like we do in the rest of the Northern Rockies in fact what we're seeing is the result of very young volcanic features called the Yellowstone volcanic field in the mountains that were once here were blown away during these giant volcanic eruptions and we have the very very Norma's amount of heat that resides today and that he drives Yellowstone's world-famous geysers and hot springs in the end it is Earth's heat that makes the park a tourist destination the heat comes from a magma system called the Yellowstone hotspot this heat source lies just two miles below the surface of the park from 1923 to 1985 the whole of the Yellowstone Caldera Rose about three feet today Yellowstone is subsiding roughly half an inch a year it is as if this large piece of Earth rising up and down is breathing all of this relative motion in just a few decades tells geo scientists this is a giant living geologic feature Yellowstone right now is also the site of very very intense earthquake swarms it's the heat that pressurizes the near surface of the earth lifting it up and down as it creaks and groans it generates earthquakes the earthquakes marbs sometimes are so intense that you literally can feel hundreds or thousands per day Bob Smith's investigations of Yellowstone's geology lead to an ominous conclusion in the next hundred years or five thousand years there will be an eruption here just as Old Faithful blows every 72 110 minutes volcanoes have erupted along the Snake River Delta about every six hundred and thirty thousand years and one is about due as our cross-country trip moves east early leaving Yellowstone behind the Rocky Mountains loom large in our path 70 million years ago they formed a surprising boundary along what was once a great Inland Sea the southern Rocky Mountains evolved differently than the rest of the Rockies to learn their history you need to look back to when the interior of North America was flooded forming the Inland Sea way the Cretaceous Inland Sea started around 90 million years ago it started down from Canada and connected with an arm that was coming up from the Gulf of Mexico until it split North American half dr. ken carpenter from the Denver Museum of Natural History has had a lifelong interest in the Cretaceous inland Seaway and the creatures that lived there during the time of the Seaway the climate was very different today Colorado is dry but tens of millions of years ago the environment was very hot humid and much wetter 90 million years ago I'd be laying on the beach today I'm over a mile high nearest ocean is love and herd miles away this rock extends for hundreds of miles all along the front of the Rocky Mountains the sandstone represents beginning of the Seaway coming into North America in this ocean there are all sorts of marine animals like please the sores with their very long necks we know that ninety million years ago this was seabed because of the type of ripple marks that we have here these are very symmetrical on both sides and that forms when water oscillates back and forth roughly about 65 million years ago forces inside the earth Yente push up draining away the ocean today these rocks are tilted to over 50 degrees let me just lesson that we can learn by studying the Seaway and the rocks out here is that theorist is always changing it's never the same what we have here today being high altitude some day yet again maybe out in the sea floor the earth is in constant motion and this is good evidence of that during the millions of years that the Inland Sea Way existed layer upon layer of rich sediments were deposited which became the base for the Great Plains today the Great Plains is a super productive crop growing area about a quarter of the world's total production of wheat rye corn oats and barley are grown here just beyond the Great Plains in the middle of the continent is the largest freshwater lake system in the world the Great Lakes from the moon you can see the lakes and recognize the familiar shape of Lake Superior and Lakes Michigan Huron and Erie they are also one of the youngest natural features in America and like many aspects of America's face they were formed during the last ice age when glaciers flowed down from the Arctic leveling mountains carving valleys and gouging lake basins the last ice advanced began around one hundred thousand years ago and reached its peak eighteen thousand years ago the massive ice sheets were over two and a half miles thick in places they would have dwarfed the skyline of Chicago had it been present as the ice sheets flown south around 14,000 years ago the ice sheet began to retreat as Earth's temperatures rose as the glaciers melted the resulting water filled the huge holes carved by the glaciers creating the Great Lakes dr. Tom Johnson is the head of the large lakes observatory at the University of minnesota-duluth tom is taking his graduate students out on the research vessel Blue Heron to study the geology biology and chemistry of Lake Superior oh that's 46 degrees 46 minutes Lake Superior of course is a relatively young Lake it's only been in existence since the Ice Sheet last left here some 10,000 years ago as the Ice Sheet retreated glacial runoff created several lakes in this area one of these lakes formed eleven thousand years ago was glacial lake Duluth which today would cover the current city of Duluth Minnesota you see the for coming breaking surface right now so what do we have here it's a very very stiff clay which is essentially the bedrock of the Wisconsin shoreline this material was laid down in glacial lake Duluth at the end of the last ice age as the SU was melting glacial Lake Duluth was about 300 feet higher than the present lake as temperatures continue to warm and the glaciers retreated northward without the immense weight of the ice sheet the land began to spring back since the last glacier has melted away the eastern end of the lake is rebounding from the release of the weight of the overlying ice that had been here during the last ice age and because the ice was thicker at the east end of the lake where the outlet occurs East End is coming up fast and as it comes up faster it has the effect of tilting the Lake Basin causing water level to rise this end of the lake at a rate of about a foot per century so it's a very dynamic part of the lake the Great Lakes cover more than 94 thousand square miles and hold an estimated six quadrillion gallons of water about one-fifth of the world's fresh surface water supply and nine tenths of the u.s. supply if this were spread evenly across the continental United States it would cover it with water nine and a half feet deep not every feature of America is as young as the Great Lakes the most prominent topographic feature of the eastern US is the Appalachians now stooped with age 250 million years ago they stood as tall as the Himalayas are today the Appalachians are the bare remnants the roots of what they were 250 million years ago during the time of the great supercontinent Pangea then the Himalaya sized Appalachians marked the suture in the middle of the supercontinent where North America Africa and Europe had collided back then present-day Washington DC would have been opposite Western Sahara Africa close to 200 million years ago an gia broke up a rift opened that separated North America Africa and Europe giving birth to the Atlantic Ocean at the end of the age of dinosaurs 65 million years ago the Appalachian Mountains had largely been worn down eroded by water through time and the sediments flowed out into the Atlantic Ocean as they still do today the coastline of the american eastern seaboard began to take shape but there were a few modern features that still took more time to appear and one when it did happened in the blink of an eye about 35 million years ago out of the blue were more accurately in the black a comet or asteroid struck earth in what is today the southern chesapeake bay it was the largest impact identified what is today the United States the impact left a massive crater in the crust which was rapidly filled back in by rushing ocean water the crater lay hidden for millions of years completely unnoticed on the surface no one had an inkling about this ancient impact however over the years scientists began to discover several tantalizing clues that something important had occurred in this area of North America then in the 1990s oil companies exploring for deposits of oil and gas and lower Chesapeake Bay gathered seismic reflection profiles that reveal the unmistakable shape of an impact crater the US Geological Survey in cooperation with the International continental scientific drilling program drilled a hole more than a mile long into the deepest part of the crater this is the core they pulled out Jay Wright Horton is one of the geo scientists for the USGS working on this mystery a good way to sample a block of Earth's crust that's unknown is to hit it with a big meteorite and scatter pieces at higher levels where they can be sampled for study the Chesapeake Bay impact crater is the seventh largest on earth and the largest in the United States it's especially interesting because it was an impact the end of the ocean that was several hundred to a thousand feet deep at the time the crater is about 53 miles in diameter roughly the size of the state of Delaware and deeper than the Grand Canyon Greg Gaughan is a geoscientist with the USGS here's a particularly good example of an ejecta clast this is a crystalline rock that was probably shocked as it's at several kilometers down in the ground then it was ejected out of the crater and then within minutes washed back in with the return of the seawater into the crater here we get to a point where rather than broken rocks you see the rocks are intensely fractured and this has a very graphite rich dark matrix our hands were black from handling it at the drill site since there is no direct evidence of the crater on the surface cores like this provide scientists a way to piece together the mystery of what happened 45 different research teams from 13 countries are working on this project pieces of core will be cut up and sent to laboratories around the world for study the samples geologic chemical and biologic properties will be analyzed the core is in 3-foot sections and laid out on tables in a football-field-sized room at USGS headquarters in Virginia it is hard to visualize just how long a mile drill core is it's pretty long and it is equally amazing the geoscientists are able to piece together the details of an ancient event whose evidence was hidden so far below Earth's surface well for decades now we have known that an area of salt water comes inland at the Chesapeake Bay around Virginia normally along the coast you find water that's either fresh or salt or somewhere in between but in the crater the water is actually saltier than seawater the impact of the crater 35 million years ago continues to affect humans today all of the development and increasing population is putting more and more demand on the available groundwater the concern is that in the future saltwater from the crater will start to make it difficult to provide fresh water to the communities in close proximity each landscape is like an ancient text containing a detailed account of its creation in the Connecticut woods scientists have made a fascinating discovery trees stand tall today that grew in New England when it was still a tropical paradise here we are on a rainy day in Connecticut and a little piece of native woodland that still survives here on the grounds of dinosaurs State Park dr. Leo Hickey of Yale University studies the evolution of flowering plants and what that tells us about climates of the past if we were to go back to the Cretaceous and look at the landscape with the vegetation on it in general it wouldn't look too much different from this in general aspect 80 million years ago Connecticut lay further south near the young Atlantic Ocean at that time this part of New England would have had a climate very similar to subtropical areas like Rio de Janeiro and we're talking about temperatures of 60 degrees mean annual temperature to 70 degrees you'd never have snow here and of course it would be dinosaurs the Cretaceous was a very long period it lasted over 60 million years was much warmer than at present there was much less difference between the winter and the summer this was a very important aspect of these climates with less substantial changes in seasons a wide variety of plants could thrive in this subtropical environment many different plants inhabited this area that no longer do but some plants were able to adapt like any modern woodland most of these trees that you see in the background evolved within the last 10 15 20 million years a few of them are Cretaceous survivors or survivors of the of the dinosaur era I'd like to point a couple of these out to you um over here right on the edge of the forest if something called lindara benzoin it's a spicebush it has these wonderful tongue shaped leaves with with smooth margins and if you push it up has a wonderfully aromatic smell this is a member of what's called the laurel family and the first of these that we know is approximately 90 to 95 million years ago this is sassafras and these leaves are again if you crush them up they have a very nice aromatic smell to them and again these are defense compounds now one of the interesting things about plants is that they are rooted they they're there in place they never move of course that's a obvious you don't need a scientist to tell you that and they have to take the weather pretty much as it comes so they have to develop physical adaptations to their climate so the plants the flora is actually intimately related the features of the flora to the kind of climate conditions that it's under low seasonality is really important and with low seasonality you can grow a lot more different plants in the same area under the same temperature conditions so what you get is a tremendous increase in the diversity of plants in the Cretaceous much more diverse flora at this latitude than there is today climate obviously affects living things like plants but it can also have a dramatic impact on shaping the landscape around us the Palisades in New York are a line of steep cliffs on the western bank of the Hudson River and are a relic from the fragmenting of Pangaea and the opening of the Atlantic the stress and strains of the breakup opens several fractures near modern New York magma rose through the ruptures in the crust and cooled before reaching the surface water erosion eventually exposed the basalt columns creating the Palisades then 35,000 years ago a cooling climate further shaped the Palisades and the Hudson River Valley massive ice sheets advanced south into this area when they encountered the resistant basalt of the Palisades it resisted the scouring of the ice sheets which led to the gouging that would become the Hudson River channel as they gouged in advanced ice sheets picked up and carried them from the debris this glacial earthmoving created Long Island and defined a good part of Manhattan the climate changed again 18,000 years ago and as the ice sheets retreated sea levels rose back flooding the Hudson drowning the coastal plain and bringing saltwater well above the mouth of the river this created the island of Manhattan with its protected waterfront that would eventually make New York one of the most commercially viable cities of the world the deeply eroded Hudson River bed extends beyond the current shoreline it deposits sediment from all over New York out into the Atlantic Ocean at the edge of the continental shelf over the ages this has built a massive sediment Basin that is about eight and a half miles thick it is one of the largest geological features in the world and lies right off New York it is in sediment basins like this that natural resources like oil and natural gas are formed over time gyeo scientists study river deltas today to better understand how the formation processes work and how oil and gas are produced and trapped in these formations when we studying rocks there are very few ways to actually get information we can go to the field and look at real rocks but we only see glimpses of them so this is a way to develop an entire sedimentary system where we can kind of observe all the different aspects of it right here in front of us one of the things you find is at least in the case of river deltas is a pretty robust repetitive pattern is the the nature of the processes that occur at the channel mouths geo scientists David Hoyle and Ben Sheets model river deltas comparing them to real-world situations so what you see here is a river delta this is our third foot Delta made from cohesive sediment sheets and Hoyle have developed their own mixtures of sand and clay to use in their experiments that mimic how sediments deposit their simulations are the same in every detail as real-world river deltas just on a smaller scale basically the dice shows us the channel patterns now in nature a Delta like this may take thousands of years to build we can build something like this in a couple of days and look at all the other complexity and the big test here is is to get all the complex features of a real Delta so there are large accumulations of oil and gas in natural Delta's and what we're developing here is an experimental small scale model of natural Delta's basically trying to figure out how the sands and the muds are distributed the oil resides in the sands and the muds that act as barriers to stop the flow of oil so this small-scale experiment can help us understand where the muds and the sands are it gives us some predictive ability about what we might find in the subsurface and where the sand in the mud might be it's hard to imagine oil fields like those in West Texas just 40 miles off lower Hatun but the Hudson River has deposited sediments over 30,000 feet thick that at some future time may well become a large reservoir of oil and natural gas we have to remember that earth is constantly moving working recycling and changing every moment of every day to truly understand and appreciate America's spectacular and varied landscape requires understanding the causes and effects that brought things to their present form we then might be able to predict where it's all going in the future and understand how better to live here on the face of Earth you

Channel: American Geosciences Institute

Views: 856,618

Rating: 4.6447835 out of 5

Keywords: United States (Country), United Kingdom (Country), Earth, Earth Sciences, Geology, Ice Sheet, Climate, Documentary, American Geosciences Institute, Mt. Ranier, Cascadia, Subduction, Channel Lands, Gold Deposits, Asteroid Impact, Mesozoic, Streams

Id: 1iTUAUmF-N4

Length: 45min 38sec (2738 seconds)

Published: Tue Feb 19 2013