The Mysteries Of North America's Great Lakes | Naked Science | Spark

of all the drinking water in the world, one fifth is stored in one place the Great Lakes are so large they are like inland seas so vast that they create their own climate without them a large part of North America would be arid they are filled with enough water to flood the continental United States 9 feet deep but water levels are changing dramatically to understand where the waters are going you have to know where they came from and unlock the

mysteries

behind the Great Lakes the Great Lakes deserve their name they cover a area larger than Utah and contains 5,500 cubic miles of fresh drinking water, the deepest of the five

lakes

.

Lake Superior is more than 1,300 feet deep. Lake Michigan and Huron provide drinking water to more than 10 million people in Chicago and Detroit, between Lake Erie and Ontario lies the mighty Niagara. Falls at their peak More than 40 million gallons flow over the falls every minute It provides electricity to approximately 5 million homes. The Great Lakes are unique, but how did these five vast

lakes

form? What force was so powerful that it reshaped Solid Rock and carved such deep depressions beneath? A sea of ​​water and silt The lakes cover the evidence of their origins, but on an island in Lake Erie a clue is exposed Kelly Island sits on an ancient rock The rock is marked by strange grooves more than 15 feet deep depth and 400 feet long if If we were to look into the depths of the lakes down to the bedrock, this is what we would see.

Dr. Jeff Dick of Ohio University is looking for clues about how the lakes formed. The furrow we are sitting in here provides a very interesting tidbit of information about how the

great

lakes formed the area we are in in this furrow was obviously extracted by some Force, but what Force sculpted these lakes. One of the most dramatic sculptures on Earth is volcanism. Boiling magma erupting from the depths of the Earth as it cools and hardens can produce incredibly strange geological formations. Did volcanism do it? the rocks on Kelly Island contain the answer small coral fossils when the rock melts the fossil record is usually destroyed if lava had formed the grooves these fossils would probably have been obliterated the next suspect is water if water carved the Grand Canyon why not the Great Lakes but water has an alibi fractures in the Rock if a stream had been formed by running water a river it is more than likely that that serpentine river would have taken advantage of this weakness in the Rock and actually followed it, meaning that the fractures would direct where the current flows and in this particular case the grooves run almost perpendicular to them suggesting that perhaps there is another Force at work here, so if volcanism and running water They didn't shape the furrows.

What did he do? There is other suspicious ice, but how do you sculpt simple ice? Where better to discover it than the most spectacular frozen landscape on Earth? Iceland this is the Vat Neok glacier is the largest ice sheet in Europe It covers 3,200 square miles, that is, more than twice the area of ​​Rhode Island In places it is more than 3,500 feet thick, geologist Andy Russell knows it as his backyard, this glacier, although it may seem like it's sitting there and, uh, you know quite passively that the real ice is always advancing even though the edge of the glacier may be stationary.

This time-lapse video shows the glacier's motion accelerated hundreds of times behind the leading edge. The ice moves up to 3 feet per day with a heavy step. A mile-thick glacier exerts about 2,000 pounds of pressure per square—that's the weight of 115 cars in a square foot of land—for its entire volume of ice, it's not as difficult as it seems to cut solid rock and form ice basins. Great Lakes ice needs another ingredient Andy Russell demonstrates I'll take some ice that has a smooth surface and we'll drag it through the aluminum foil. There's actually very little damage to the aluminum foil, so now we'll move on to the dirty ice.

The dirty ice is embedded with little rocks and stones that I can see it has all this sand in it and let's see what it does to the aluminum foil. The aluminum foil is shredding. This is how a glacier damages as it travels. The glacier collects stones and balances the weight. of the ice holds them against the bedrock, then the moving mass runs over the land like a huge sheet of sandpaper when the glacier finally melts, leaving behind a vast depression filled with glacial meltwater, normally impossible To see glacial erosion in action, the process is hidden beneath a solid sheet of ice, but here in Iceland the base of the glacier is exposed.

He shows Russell how ice crushes solid rock and explains how ice could carve the Great Lakes. We have layers of ice that you can see here mixed with layers. of rubble or is it dirt here and also here and obviously this large part of uh Rock here this rock the rock tells us several things all these little scratches that crisscross and the fact that this surface here is extremely flat tells me that that rock in It has actually been on the bed of the glacier, it has been trapped in the ice and then it has been crushed against the bedrock.

This glacier is melting, and as it melts, it drops its load. Iceland is full of thousands of fallen rocks. It is this action of rock rubbing against bedrock that may have excavated the strange grooves on Kelly Island, but where is the proof that a giant glacier passed over the Great Lakes area here, near the shores of Lake Ontario? Scientists call this an erratic rock, meaning it doesn't belong here. This giant rock is made of granite. type of rock not found within 100 miles of this area, like the rocks in Iceland, were trapped inside the ice for thousands of years, dragged through the bedrock, and then dumped into their new home.

The glacier that moved the rock must have been enormous, proof again. Found in the rock of Kelly Island, from the chemical composition of microscopic fossil shells, scientists can tell that the water was once much colder. Small clues lead to a big conclusion: A glacier up to 2 miles thick covered most of Canada and a large part of the US. For more than 1 million years it was called the Laurentide Ice Sheet, the massive Glacier Moving forward, and backing over the land back and forth as he did so, he excavated the five huge lake basins, the ice sheep passed over the Great Lakes, but how long did the ice take? to carve solid rock and form the Great Lakes basins.

Geologists believe the Lauren tii layer moved across North America for more than 1 million years, but how long did it take to excavate the five vast lake basins? In Iceland, the vokal glacier erodes bedrock. Just as the Laurentide once did in the Great Lakes, Andy Russell measures the crushed rock carrying sediment, this equipment measures the turbidity of the meltwater, the turbidity of the water gives us a rate of sediment transport in the river and If we average that and scale it up over longer periods of time, we can determine how fast the basin is eroding, measure the sediment produced, average it over time and this glacier grinds down about 1 T of solid rock every 100 years, but did the Laurentide erode the rock at the same rate?

After all, it was more than 1,000 times larger than the Vokal glacier. John Men has come to Mohawk Bay, on the shores of Lake Erie, to discover the answer and it is hidden in these cliffs. They look like mud, but they are ancient rock sediments. They were once solid. The bedrock was crushed by the Laurenti Ice Sheet and deposited here based on the evidence that we are trying to sample here today and we hope this illustrates how the Great Lakes basins formed and developed. These small rock particles contain a secret menz that sets the sample in resin and cuts it into thin sections.

Typically glacial erosion produces rock grains with irregular edges. These grains are almost round. If you look at this particular thin section, you can see this particular piece of rock and you can see around it the effects of the type of rotation. This is indicative of the sediment moving beneath the ice sheet and rolling and turning beneath the ice; In other words, the sediment has been turned, moved, rotated and cut over and over again, but how can a glacier produce both irregular and smooth grains of rock? explanation some of the ice within the laurentide glacier moves faster than other areas of ice the rapidly moving ICE is called the IC stream Ice streams are like rivers of supercooled water, water that is well below the freezing point but that does not solidify.

These rivers can flow up to 3,000 feet per year 10 times faster than the surrounding slow solid ice working 10 times faster potentially can dig 10 times deeper more evidence that the Lauren tide contained fast ice and is located next to Lake Ontario this is An aerial photograph of the coast showing strange elongated hills these are pieces of sediment called drumlins when the glacier retreated they were left behind this is how they formed. I think it's something interesting. This piece will make 52 layers viewable on mobile devices or the big screen, all free, no subscription required, so if we produce a drop of toothpaste and take this as the base of the ice and as the pretty deforms, the toothpaste also deforms and we produce this beautiful linear.

You can actually see the little lines on Drumlin shapes like Streamlight that are actually produced by just moving. interface upon interface, just as fast ice leaves a trail of long, thin drums, it also tends to carve long, thin lake basins, if fast ice alone had carved the Great Lakes, the ancient ice sheet might have It took only 100,000 years to be uprooted. Millions of tons of rock buried in fine sediments were washed away by meltwater and dumped into the Atlantic Ocean, leaving behind five huge basins, the deepest Lake Superior, more than 1,300 feet, the Great Lakes, but when did the lake melt? huge Laurentide glacier and the basin filled? with life-giving fresh water Francine McCarthy has a clue a 12T mud tube called a sediment core the sample was taken from the bottom of Willow be bog a swamp between mystery lakes and Ontario this keeps a very good record of what happened when people were Here to maintain history, the core is made up of pollen grains from mud and sediment deposited in the water when the lakes were formed.

We removed material for radiocarbon dating and the dates are about 1700 years ago here, about 7500 years ago here and about 9000 years ago. Near the base, cores reveal that water was present at least 9,000 years ago, but beneath the 9,000-year-old layer is an even older one. It is the last layer before touching Bedrock, so it must be the first layer deposited in water if McCarthy can date it. She can determine when the freshwater arrived and reveal the age of the lakes, but to date the layer she needs organic material. She can see the color contrast between the very inorganic material and that of the swamp.

This is impossible to date using conventional radiocarbon dating techniques because you can see that there is very little organic material here, just rocks and clay, a dead end, but why are the first lakes lifeless? To find out what the first Great Lakes were like, we must return to Iceland and the vokal glacier here at the base of the The glacier is a newborn lake, its basin carved by ice and filled with meltwater. This is what the Great Lakes looked like tens of thousands of years ago, and just like the first lakes, this place is dead, there was virtually no life in these proglacial lakes, it's very cold.

It's a very harsh environment, there's very little light, so their whole ecosystem can't really get going. The reason for the strange milky color of the water, these lakes are loaded with bedrock sediment washed down from the glacier, this sediment blocks light and without light small organisms like algae cannot survive there are no plants there is no food there is no life as the voko glacier continues to melt more water will flood this lake and dilute the sediment it will eventually settle to the bottom just as it did thousands of years ago in the Great Lakes. the pale gray layer McCarthy discovered the remains of the mystery scientists have to find some other way to date the age of the lakes the answer could be hidden in one of the most spectacular geological formations in North America Niagara Falls Niagara is the North America's most powerful waterfall and one of the most impressive features of the Great Lake on average 150,000 gallons are poured every minute enough to fill more than 60 Olympic-size swimming pools.

Niagara has the answer to a prehistoric mystery: when did the Ice Retreat and the Great Lakes fill with water? John Men has come to investigate his the first time he was so close to the falls it is absolutely incredible if you seethe volume of water coming per second, all the water from central North America is flowing here, as we are, fantastic, it's possible to date the falls. arrival of water to the Lakes because Niagara behaves very strange The Falls move every year they step back a full 12 inches towards Lake Erie the reason for this movement is The Rock The Falls are built on two layers of rock at the top the falls are a hard layer of limestone known as cape rock below there is a softer layer this is a piece of Queenston shell which is the weakest rock beneath the cape rock for this regional geology of the area and in fact , it is very easy to break as you go.

I can see Bingo, the weak shale at the base of the falls is relentlessly pounded at up to 70mph, the constant hammering eroding the shale beneath and undermining the cape. The rock on rock c is left like a lime pry effect and then it just breaks and from time to time it breaks quite dramatically, in fact if we look at the falls there is a huge rock that has actually fallen into The last 100 years, in a sense, you can look at Niagara Falls as if it were a continuous process of destruction, perpetual destruction. The perpetual change of destruction means the falls act like a giant clock, a huge CL clock that allows geologists to date the age of Niagara and the lakes themselves back to when 100 years ago the falls were eroding at 3 to 4 feet per year. as water was diverted for hydroelectric plants. feed the erosion rate has slowed, but the falls are still eroding about half an inch per month.

Over time, hotels, casinos, and more will be left behind in the falls' trail as the falls retreat and leave this tourist area. in isolation if the falls continue to erode at this rate in about 50,000 years The falls will reach the base of Lake Erie itself as the falls recede, carving a giant canyon, the Niagara Gorge, 3 m downstream from Niagara, geologist Francine McCarthy can date the Great Lakes When searching for the birthplace of the fall, the secret is hidden not in rocks but in clam shells. Well, that's perfect, we can identify the species. It's definitely the kind of thing we want to radiocarbon date in the lab.

This species of mollusk lives in Lake Erie. was swept downstream and over the falls the rising water wedged the mollusk into cracks at the base where it died the falls moved on the shell left behind by carbon dating shells like this McCarthy can show that Niagara Falls roared over this place Exactly 7,000 years ago The water level would have had to have covered this area to be able to deposit the small aquatic clams in the nooks where we found them, further proof can be seen in the strange rocks scattered throughout this area, these holes were cut in the rock from the constant blow. of water over the falls, but this is not the birthplace of Niagara.

The further McCarthy walks from the falls, the further he goes back in time and the older the shells he discovers by analyzing shells found along the gorge McCarthy reveals the life cycle of the lakes from From Niagara's Spectacular Current Location to its location in 1678, when the first written account was made Downriver to the whirlpool rapids 5,500 years ago via Niagara Glenn, where the McCarthy shells reveal its location 7,000 years ago to Queenston 10,500 years ago and finally 7 m downstream from the falls. Where a natural ridge called the Niagara Escarpment runs through the land, scientists discover the oldest shells, yet Niagara Falls is 12,600 years old, it has been running since water began melting from the Laurenti Ice Sheet and if Niagara Falls is 12,600 years old, so the Laurentide glacier must have receded at least 12,600 years ago, exposing the two lower lakes, Erie and Michigan.

The mystery is solved like Niagara. The Great Lakes have continued to evolve over the millennia, but some changes occurred much more dramatically than anyone imagined. Today, rainfall in Lake Superior lasts 204 years. years to travel through all the other lakes before reaching the Atlantic Ocean, more than 2,000 m away, the Great Lakes flow east and have always been thought by geologists to be scientists who study fossils in the Gulf of Mexico They discover surprising species, forcing them to reevaluate what they thought about the Great Lakes Scientists analyzing 14,000-year-old shells discover that water in the Gulf of Mexico must have been less salty than today, but why only one water source sweet was big enough to dilute the gulf?

Fossil records from the Laurentide Glacier suggest that the mwat drained south along the Mississippi River to the Gulf, but then, nearly 13,000 years ago, a force from the Titanic diverted the flow from the south to the east. The question is what force was powerful enough to divert the Great Lakes. 13,000 years ago, an unknown force diverted the flow of meltwater from Laurentide Glacier geologist Alan West searches for answers on the shore of Lake Michigan. This is a visual line that is actually where our

great

est interest lies. The big paws actually started right at this line in the sediment.

West finds small spots the size of sesame seeds. are made of carbon West believes they are all that remains of a vast forest incinerated in sweltering temperatures, but the most important clue lies within each grain, a dazzling secret: these little black dots are almost pure carbon and when we check them with With an electron microscope we found that they contain millions and millions of diamonds, each diamond is a thousand times smaller than the head of a pin, they are known as impact diamonds, they are formed under intense pressure, but what created them was something big which hit this area at high speed and filled up. big swipe Allan throws a sample onto a magnet incredibly, it contains metal, definitely, magnetic grains in there, you can see them coming out.

The magnetic grains are iridium. Iridium is extremely rare on Earth, but common in space rocks. West's theory is 12,900 years ago a massive mass. The comet hits Earth and showers the region with iridium. Forest fires devastate the area and destroy all vegetation. The wave of fish breaks part of the Laurentin glacier. Billions of gallons of water are released. It's well known that when these meltwater floods occurred, they were very, very abrasive, they can change the shape of valleys, they can scour bedrock, so it's very possible that they excavated the Great Lakes deeper or at least they have removed the sediments that were already there.

Thousands of tons of rocky soil and debris are swept southward like a giant plug blocking the passage. Mississippi, the water recedes. Lake Ontario swells and bursts its low eastern shore and the St. Lawrence Seaway opens. All the evidence shows that the Gulf of St. Lawrence opened and the water went east, but stopped going southwest. He believes that everything happened in just a few months since the lakes flowed into the Atlantic Ocean to the east, the New Direction allowed small settlements to become the large cities of Montreal and Quebec. Rarely does the course of history change so suddenly and dramatically, but the evidence is circumstantial if a comet hit where the crater is in 1999 at the bottom of Lake Ontario.

Geologists discovered a crater half a mile wide. It doesn't have a date yet. West believes it could be a fragment of the comet that deflected the water. No other craters have been found, but West is not surprised. the comet could have done its damage and just melted because comets are mostly ice, this is the perfect crime, the ice bullet shoots someone with an ice bullet and you can't tell who did it. The Earth was hit by an ice bullet, actually thousands of them and So the evidence is minimal As the last ice age ends, the five Great Lakes basins slowly reveal themselves and fill with fresh water , but there is a big difference between these early lakes and the ones we see today: they are not linked together.

We took a force of nature more powerful than a comet today the Great Lakes are connected through a network of rivers and canals a 2,000 m water system this was not always the case the upper lakes Superior Michigan and Huron were not always connected to the two lower lakes Erie and Ontario Francine McCarthy is trying to figure out how they came together. We have taken some samples along the shoreline of Lake Ontario and Lake Erie and are going to look under the microscope at small seeds and pollen to discover the age of the samples and what type of environment they were deposited in 5 miles inland from Lake Erie.

McCarthy discovers a small clue wild rice this is incredibly strange wild rice does not grow inland wild rice needs a kind of agitated, well-oxygenated water to be happy The fact that there was a lot of wild rice indicates that the water level in the lake Erie was taller than it is today. Lake Erie must have been much larger and more turbulent. The wild rice date of 4,230 years tells us that water levels rose rapidly instantaneously in both the area and the Ontario basin, but why does McCarthy have a theory? More than 4,200 years ago Lake Huron swelled and burst its southern shore, a torrent of water pushed southward, Lake Erie suddenly expanded and wild rice took root in its disturbed waters, the St Clair River opened and the Lakes came together, that is when we begin to see truly modern conditions, for 4200 years ago there has never been any other way for water to flow from the upper lakes but through the St Clair River into Lake Erie, over the falls and into Lake Ontario, but why? ferrets swell and flood the south the mystery deepened when scientists noticed something strange was happening in the Great Lakes in each lake the water level in the

north

is falling but in the south it is rising what mysterious force is behind these Strange phenomena Professor Doug Hunter and divers Luke Kurn and Kathy Trackx delve into the lake's past to find evidence of ancient water levels.

They begin their investigation in the southwest corner of Lake Huron in the port city of Lexington. They need evidence to demonstrate whether this water level imbalance is a recent phenomenon or whether it has been happening for millennia. Today we're going to put divers in the water and as we dive we're looking to see if we can find anything that shows that this is where the lake levels were a few thousand years ago. Lake Huron is more than 700 feet deep in some places, but the area the team is interested in is only 40 feet deep right now. We are about 2 and a half miles east of Lexington Harbor below us, in 40 feet of water, an area where we are suspicious.

There may be some interesting finds that would give us insight into the history of the Great Lake. This section of the lake bed has never been surveyed. The team scours every inch for evidence of past water levels. They are looking for something out of place. Some clue. To this strange mystery 40 minutes after the dive, the team finds several large pieces of wood only from this wood. They can't tell if trees ever grew here or if it's just debris thrown from a boat. They need evidence like this. A tree trunk. still rooted in the lake bed, these stumps have never been seen before, this proves that trees once grew in this exact spot, a real discovery, there is a wooden boy that was a great dive, you can see whole trees falling and They just went out onto the sand and down, but once we found the tree stops and you could see the roots of the trees, it had to be Shoreline.

This part of Lake Huron was once a cedar and pine forest. Nowadays, you have to dive 40 feet to reach the trees. but could you have ever walked here and not even gotten your feet wet, when could you have walked among the trees, these stumps have to be carbonated, but samples from other places in the lake have already told us their age, we discovered that the most recent It was 6,400 years before present, the oldest was about 7,900 years before present, so it's a pretty long range, a pretty big range of dates. 6,500 years ago, Lake Huron was a fraction of the size it is today. , a forest flourished at its southern end. 1500 years later, the water crept south, the south end was flooded and the forest drowned, the St Clair River opened and Lake Huron joined Lake Erie, the overflow thundered along the Niagara River and fell over the falls and the five lakes came together, but what caused this dramatic transformation?

And is it still happening today? Mike Kramer of the Geological Survey of Canada is investigating a strange anomaly in which water levels in theGreat Lakes are falling in the

north

and rising in the south. Kramer works on a remote spit of land next to Lake Ontario. It's not the water level, he's monitoring what looks like a garden shed, it actually contains state-of-the-art GPS technology. We are using a GPS receiver to monitor the movement of the structure every 30 seconds. The antenna is bolted to the floor and works. up through the roof is very stable in other words Kramer is studying whether the shed is going up or down this GPS receiver picks up signals from satellites orbiting the Earth the equipment is so sensitive that it can detect movement down to the millimeter as a result Kramer can determine the exact elevation of the shed and therefore the ground it sits on.

His findings are striking: The Great Lakes region is rising by 1 per decade in the north and sinking by almost 1 per decade in the south. This part of North America is tilting and Pivot Point runs directly across the Great Lakes, the tilt is imperceptible to us but it affects the lake's water level. We have a bowl of water that represents a lake. This end is north, this end is south and if we can imagine how the earth tilts. the water levels are rising in the south and falling in the north, it looks like the entire water level is falling and it is actually a land that is rising, the changing land levels are small, but over time all those inches They add up and finally the inclination is what drowned a forest.

But what force is powerful enough to tilt a large part of the North American continent? Scientists believe it is the opposite of the force that compressed it. The Earth's surface can actually be crushed if the weight is heavy enough. Few forces are capable of compressing the crust. One is ice. the laurenti glacier weighed about 10 million trillion tons once it reached a certain thickness the glacier depressed the crust 1 foot for every 3 feet of ice left a dent up to a half mile deep about 20,000 years ago the ice had covered the largest part of Canada and the great weight of that ice had substantially depressed the crust and when the ice retreated and melted the land beneath it began to recover.

The rebound began when the ice melted tens of thousands of years ago and continues to this day at about a tenth of an inch per year. The ice sheet was much thicker in the north than in the south at its thickest point. It compressed the Earth more, so when the weight was removed the Earth bounced further north. This imbalance causes much of North America to tilt. Combined with a warmer climate and less precipitation recovery, it is changing the contour. of the Great Lakes if water levels continue to fall in the north, vital transportation routes will be reduced, industry hydroelectric plants and millions of people could be affected, eventually the crust will recover to approximately the position size that It had before the Laurentide Glacier moved over it and the water will find its level, but until it does the future of the Great Lakes will be as dynamic as its past.