The Late Pleistocene was a period of "fierce weather" that far surpasses today's climate scare stories. There were sea level rises of 30 meters in just 200 years and temperature rises of 8℃ during only 10 years. Huge lakes emptied their contents of icy water into nearby valleys and plains almost overnight, in ways that changed the landscape forever. All these dramatic climate events happened without any human CO2 emission or human involvement at all, which shows that we have completely exaggerated notions about human influence on the Earth's climate.
1. Dramatic climate changes
The absolute maximum of the last ice age took place around 26,500 to 19,000 years before the present. In Europe, the ice covered all of Scandinavia and the Baltic Sea area right down to northern Poland and Germany. In North America, the ice sheet reached down to the Great Lakes between Canada and the United States. The ice caps were several kilometers thick.
This article describes the violent climatic events that occurred in the late Pleistocene in connection with the melting of these enormous mountains of ice.
Timeline of Earth's geological periods. Time progresses from right to left. The glowing inferno just after Earth was formed is called Hadal. Water vapor condensed in the Archean, and an atmosphere of nitrogen and methane arose along with the first rocks that we know of. In the Proterozoic, cyanobacteria produced oxygen, which oxidized iron and methane, at the end of the period life appeared on the sea floor. The entire period prior to the Phanerozoic is often called the Precambrian, as it was previously believed that life arose in the Cambrian with the appearance of trilobites.
The Phanerozoic refers to the era in which visible tangible life has existed. It is divided into the Paleozoic, Mesozoic and Cenozoic periods, which are popularly called the ancient, medieval and modern times of the Earth. The Paleozoic is the period of early life; The Mesozoic is the age of the dinosaurs, and the Cenozoic is the age of the mammals.
The Cenozoic is further divided into Paleogene, Neogene and Quaternary.
Quaternary consists of Pleistocene and Holocene.
The Pleistocene is what we generally refer to as the Ice Age and the Holocene is really an interglacial, of which there have already been many, but we think it is something very special because the entire world history has unfolded in the Holocene. It is not yet concluded.
This article describes the transition from the Pleistocene to the Holocene. Own work.
For millennia, all precipitation consisted of snow, which did not melt in the summer, but simply settled on top of previous years' precipitation and became ice sheets. But at the end of the Weichel Ice Age, the temperature rose and in a relatively short time these millennia of precipitation were transformed into meltwater, which had to find its way to the World Ocean.
Average temperature and sea level from 35,000 to 15,000 years before present related to present level (1990) from L. David Roper. The blue line represents the temperature and the red shows the sea level. The thin black line represents sea level smoothed with a 10 period moving average. Time progresses from left to right. It can be seen that the surface level of the World Ocean during the "Last Glacial Maximum" was a good 100 m below today's. It can also be seen that a rise in sea level - and thus a rise in temperature - began rather abruptly around 17,000 years before the present, completely without the involvement of humans. Graf David Roper.
During the last Ice Age maximum, the water level in the World Ocean was 120 meters below today's level, as the missing water was bound as ice sheets. The ice melted within a limited number of years, at least compared to the 100,000 years it had taken to form. Thereby we can realize that it must have been an enormous amounts of water that washed through canyons and river beds in the late Pleistocene.
The oxygen isotope ratio over 40,000 years found in ice cores from Greenland and Antarctica. The ratio between heavy and light oxygen isotopes indicates the temperature. It appears that warming started 17,000 years ago in Antarctica. In the northern hemisphere, the heat only really set in about 15,000 years ago with the Bølling-Allerød warm period. This is not entirely in accordance with the expectations that one can have according to the Milankovitch theory, according to which the northern hemisphere is assumed to be climatically controlling. In Antarctica, it has been consistently cold all the time, while the Northern Hemisphere has experienced several transient periods of heat and cold. Note also the characteristic shape of the heat periods, the heat comes suddenly, certainly within a few decades, and then it slowly subsides. Temperature curves for interglacials also typically have this shape. Note also that previously there were "warming periods" in the northern hemisphere with the same shape as Bølling-Allerød but at a lower level. Graphs GRIP, Vostok and EPICA.
Drill cores from the ice sheet show that temperatures in Antarctica began to rise about 17,000 years ago, causing sea levels to rise.
Over the next almost 9,000 years, the ice sheet in Scandinavia receded into the smaller glaciers in the Norwegian mountains that we know today.
The theoretical Milankovitch insolation at 65 degrees north latitude over the last 100,000 years calculated by Berger. It can be seen that insolation was quite high during the Younger Dryas cold period. We also note that nowadays the insolation is rather low. One can imagine that the high insolation in the Younger Dryas started the Holocene, but note that earlier there were insolation peaks which were just as big and even bigger, but which did not start any interglacial. Time progresses from left to right. Section of curve from Berger, A. (2009). Astronomical Theory of Climate Change. Encyclopedia of Earth Sciences Series. Jumping.
The heating - and thus the melting of the ice - happened rather irregularly, writes Anton Uriarte. In some periods, the water level of the World Ocean could rise 10 meters or more in a few hundred years. Such a sudden increase occurred at the same time as the Bølling-Allerød warm period about 14,000 years ago, when the sea level rose by 20 m. Another warm period took place 11,000 years ago at the start of the Holocene. Some have calculated that during warm periods the sea level rose by up to 50 mm. per year, while it only varied about 3 mm. per year between the heat periods.
The temperature on the surface of the Greenland ice sheet during the "Last Glacial Maximum" (LGM), Older Dryas, Bølling-Allerød and Younger Dryas. Time progresses from right to left. Photo All-geo.
Nor did the warming take place simultaneously across the globe. The temperature rise occurred first in the southern hemisphere. Only with the start of the Bølling-Allerød warm period around 14,000 years ago did the temperature rise significantly in the northern hemisphere. This warm period was mainly limited to the northern part of the globe. Analyzes of sediments from the seabed off the mouth of the Murray River in Australia show no indication of the Bølling Allerød warm period, nor any signs of the subsequent Younger Dryas cold period.
At the end of the Weichel Ice Age in the Bølling Allerød period, scattered reindeer hunters lived in Northern Europe. Many believe they were descendants of the Cro Magnon Ice Age hunters. They had a population density comparable to the original eskimos in northern Canada. Their only CO2 emission was their exhalation and campfires.
American satirical cartoon. The dialog goes: "Ice age is ending!" - "It must be our fault".
The transition from Ice Age conditions to the Holocene was the most dramatic temperature change in the last 100,000 years, and took place in practice without any human CO2 emissions, and it far exceeds the modern 1.0-1.5℃, which the politicians cry their salty tears about. Drawing in "The Augusta Chronicle" 2/1 2007.
It is generally assumed - by some - that the reason for the end of the Weichel Ice Age must be sought in an increased Milankovitch insolation (solar radiation) in the northern hemisphere. About 17,000 years before present, the theoretical July insolation at 65 degrees north latitude was about 430 W/m2, then it increased to a maximum of just over 470 W/m2 about 10,000 years before present. Nowadays, the theoretical insolation at 65 degrees north latitude is quite low, namely back to about 430 W/m2 (calculated by Berger).
The climate of the Younger Dryas as reflected in dust in drill cores from Greenland. Wind-borne dust from China testifies that the cold and thus dry climate of the Younger Dryas prevailed at least throughout the northern hemisphere, and that it was thus not an isolated North Atlantic phenomenon. This makes the Lake Agassiz - Gulf Stream theory less likely. From Alley et al PNAS 2000.
The last phase of the actual Ice Age, around 16-17,000 years before the present, is called the Older Dryas. It was a very cold period. Dryas is the Latin name for the hardy arctic herb, grouse heather, which is characteristic of very cold arctic landscapes.
Almost 15,000 years ago, however, a significant warming started, which has been named the Bølling-Allerød warming period after Bølling Lake and Allerød Brickwork's clay pit, which are the locations in Denmark where it was first detected. The climate during this warm period was cool, but warmer than the Ice Age. Organic deposits found in Allerød showed that the plant growth was characterized by heather, birch, sea buckthorn, willow and arctic willow - not unlike the vegetation on Svalbard today. The reindeer was the dominant larger animal, perhaps hunted by predators such as wolverines and lynxes.
Accretion to the ice sheet in Greenland compared with analysis of sediments on the bottom of a lake in Venezuela. As you can see, the Younger Dryas cold period also left its mark in Venezuela. Curve Hughen et al, pers. com, Alley et al.
Some have estimated from pollen analyzes and other organic traces that the average July temperature was around 11℃, which should be compared with the around 18℃, which is the average July temperature in today's Denmark. A July temperature of about 11℃ will correspond to today's climate in northern Scandinavia or Canada. Analyzes of Greenlandic ice cores show that the temperature in the period was far from stable, there were several significant cold periods.
However, around 13,000 years before present, the Bølling-Allerød warm period came to an end, and arctic temperatures returned with the Younger Dryas cold period. However, the climate during this period was not quite as harsh as in the Older Dryas. It has been estimated from pollen analyzes and the like that the average July temperature in Southern Scandinavia was around 8-9℃, increasing throughout the period. It roughly corresponds to today's July average temperature in Alaska and Siberia.
Possible routes of freshwater flows from the Laurentide ice sheet in North America at the last deglaciation. During the melting of the North American ice sheet, huge glacial lakes of meltwater formed along the edge of the ice, including Lake Agassiz. The glacial lakes were all interconnected and it is believed that there were three outlets to the World Ocean, namely the Mackenzie River, St. Lawrence River and the Mississippi. It can be seen that the great lakes between the USA and Canada have their origin from the end of the ice age, like so many other lakes. Research Gate uploaded by Taylor Hughlett. Murton et al., 2010.
The Younger Dryas can be traced in many places in the northern hemisphere, both as an increase in the amount of dust from China in the Greenland ice sheet and as a color change in sediments in a lake in Venezuela.
Despite energetic search, however, no definite traces of the Younger Dryas have been found in the southern hemisphere. For example, analyzes of seafloor sediments off the mouth of the Murray River in Australia show no evidence of a Younger Dryas cold period.
There has been much speculation about the possible reasons for the end of the Bølling-Allerød warm period and the return of the cold climate in the area around the North Atlantic. The Milankovitch theory cannot help us; according to this theory, the July insolation at 65 degrees north latitude at this time was about 450 W/m2 and rising, which is much higher than today, when the theoretical insolation at the same latitude is about 430 W/m2.
Map illustrating the distribution of the ice in Northern Europe and the phases of the melting of the Weichel ice. The dark blue below in Germany represents the extent of the Elster ice. Brown and Red represent the extent of the Saale glaciers. The other colors represent different stages of the retreat of the Weichel Ice Age. Here it is assumed that the Weichel Ice Age had its maximum 20,000 years ago. It is further assumed that the ice edge was south of the Swedish lakes and along the coast of Norway 11,711 years ago, when the ice age ended. At the beginning of the Paleolithic Maglemose period, the ice covered the Norwegian mountains and northern Scandinavia. It thus took around 12,000 years for the ice to melt away from the Scandinavian peninsula, and there are still glaciers in the Norwegian Mountains, Iceland and Greenland to this day. 10% of the Earth's surface is still covered by the last glaciers. Map of unknown origin.
The prevailing theory is that a giant meltwater lake called Lake Agassiz, which contained more icy fresh water than all of today's lakes combined, is said to have emptied its waters into the North Atlantic. Initially, the lake was cut off from the World Ocean by parts of the glacier, but suddenly the ice dam collapsed, and the lake's entire content of icy fresh water was drained into the North Atlantic. As a result, the sea water became less salty and froze more easily in winter, the sea ice covered a larger area and thereby disturbed the Gulf Stream, which created a cold period in Northern Europe and America that lasted for about 1,500 years.
Landscape left behind by receding glaciers. The glaciers left a landscape with thousands of lakes and streams. Beneath the glaciers, the meltwater flowed through tunnel valleys, which opened at the glacier edge and formed deltas. Embankments called eskers could be formed along the tunnel valleys, which emerged when the ice retreated. As the ice advanced over the existing landscape, it could polish existing landscape formations down into elongated mounds called drumlins. When the ice edge stood in the same place for a long time, end moraines were formed, which are elongated hills. All the soil and rock that the ice dragged with it and left everywhere is called bed moraine or "till" - to distinguish it from end moraines. Everywhere small and large lakes were formed due to dead ice, which were lumps of ice that were covered by earth and rocks and thereby insulated from the heat of the sun and therefore preserved longer than the actual receding glacier. When the lumps later melted, holes were created, which were filled with water and thereby formed lakes. All the water and gravel that flowed out from the melting glacier formed extensive watery meltwater plains. Very large glacial lakes filled with icy meltwater with drifting icebergs often formed at the very edge of the glacier.
More recently, some researchers have questioned the notion of ice retreat shown in this image. They believe that the idea that the ice formed such a massive wall, which slowly retreated to the north, is inspired by our knowledge of glaciers in mountains. They suggest that in flatter terrain, the ice would simply get thinner and thinner and eventually degenerate into several separate lumps of dead ice, which then created the thousands of lakes in the post-glacial landscape. Photo UPSC Landforms of Glaciation - Geography.
The Gulf Stream must be assumed to exist due to objective geographical and climatic conditions; and it may be thought that if it did not return to its old bearing until after the lapse of 1,500 years after a disturbance, it is a testimony that it is very unstable indeed, and that its existence rests on a knife-edge, which is somewhat contrary to that it is precisely the Gulf Stream which, over millions of years, delivered all the precipitation that created repeated ice ages' enormous glaciers on both sides of the North Atlantic.
Tundra landscape seen from the air in summer with many lakes in northern Canada. The melted glaciers left a watery landscape full of large and small lakes, as we know it from Canada and Finland. In Northern Europe after the ice age, there were also thousands of lakes, which nowadays are often reduced to peat bogs. Photo Destination Canada.
In recent years, however, indications have been found of a relatively warm climate in the Younger Dryas in the area around the Irminger Sea (which is the sea east of Greenland) - both on Greenland itself and in the seabed off the coast, says Anton Uriarte. Similar observations have been made north of Iceland. It has been suggested that new prevailing winds created a more efficient exchange of heat and cold between the Arctic regions and the rest of the Northern Hemisphere.
Land uplift in Scandinavia since the end of the Weichel Ice Age. The numbers represent meters. The ice sheet above the Bothnian Bay was up to 3 kilometers thick and lay there for many thousands of years, thereby the country was pressed down by the weight of the ice. Since the end of the ice age, the land has slowly risen. In the area of the Gulf of Bothnia, the land has risen by up to 280 meters since the Ice Age. Immediately after the disappearance of the ice, the land was still depressed, and was at first flooded; these areas are shown in darker color. Land uplift in Scandinavia is still taking place at a rate of up to 9 mm. per year around the Gulf of Bothnia. From "Istid - nutid - istid" by Lars-König Königsson and Tore Frängsmyr.
A problem with the meltwater pulse theory is that evidence has been found of a second meltwater event, slightly smaller than the first, which occurred at the end of the Younger Dryas (Fairbanks, 1989). One can ask: why didn't it also trigger a chain reaction in the climate system and a new cold period?
Towards the end of the Younger Dryas, the temperature in Greenland rose by as much as 8℃ in just 10 years, which corresponds to Scandinavia's climate being replaced by a Mediterranean climate in just ten years. It is not known what caused this rapid rise in temperature.
The North American ice sheet was larger than the Scandinavian one and therefore took longer to melt; only 7,000 - 6,000 years ago did the last ice sheet disappear from the area around Hudson Bay. The glaciers on the tropical parts of the Andes began to shrink thousands of years before the warming of the Northern Hemisphere. The ice sheet in Greenland and Antarctica still exists and reminds us that we live in an interglacial period, and one day the cold will return.
Land uplift in North America since the end of the Ice Age. Since the last ice melted away about 6,000 years ago, the land west and east of Hudson Bay has risen 100 and 190 m respectively. This is not as much as the Scandinavian uplift, but in North America it has been less time since the ice left its mark roof. Land uplift still takes place at a rate of 6 mm. per year in the Hudson Bay area. Photo Wikimedia Commons.
The receding glaciers in Northern Europe and North America left behind a watery landscape filled with thousands of lakes and small and large streams, hills and depressions created by moraines and dead iceholes and everywhere an abundance of stones and gravel that the ice had dragged with it.<
The ice could be up to three kilometers thick in the thickest places, and it lay there for thousands of years. Its enormous weight depressed the land. The depression was greatest where there was the most ice, and in these places the land uplift is also greatest today.
When the Weichel Ice Age ended, the pressure eased and the land slowly began to rise, a process that is still going on to this day. Thus, the area around the Gulf of Bothnia rises by about 9 mm. per year, and the area around Hudson Bay is rising 6 mm. per year. In the opinion of some Danish researchers, the expected land uplift in Scandinavia will more than correspond to a feared rise in sea level due to the generally expected global warming.
2. Lakes in late Pleistocene
Arctic landscape full of lakes on the Tamyr Peninsula in northern Siberia. Nature of Taimyr.
vsegda-pomnim.com
When the ice retreated or simply degenerated on the spot and melted away, it left a landscape filled with thousands of small and large lakes. This happened because large lumps of remaining ice, so-called dead ice, were gradually covered by gravel and stones supplied by the continuous flow of meltwater, which was created by the continued warming. Thereby, the lumps of dead ice were insulated from the heat of the sun, and they only melted many years later, leaving holes in the landscape that became lakes. The typical landscape that emerged after the Weichel Ice Age must have resembled the landscape of Finland and northern Canada and Siberia, densely studded with lakes of all sizes.
Meltwater lakes along the margin of the North American Laurentide Glacier about 10,000 years before present. It can be seen that almost all the great lakes in North America were created by the glaciers of the last ice age and their melting. The light green area represents the ice cover 10,000 years before present, while the dark green represents the ice cover 7,000 years before the present. Photo Denton and Hughes.
Not all the meltwater ran directly into the sea through the rivers. The receding ice sheet created or exploited depressions at the edge of the glacier in many places, which were filled with icy meltwater with drifting icebergs.
The Great Lakes of North America between Canada and the United States, Lakes Superior, Michigan, Huron, Eire and Ontario, St. Lawrence Waterway as well as the great Canadian lakes Lake Winnipeg, Great Slave Lake and Great Bear Lake and many others arose as such large meltwater lakes at the edge of the ice sheet at the end of the Pleistocene.
When the kilometer-thick Scandinavian Ice Shield began to melt, the freshwater lake The Baltic Ice Lake was formed. It was a cold sea with drifting icebergs. The surface of the lake was higher than the World Ocean. Some believe that the glacial lake was emptied by an extensive flood disaster around the year 9,600 BC, but most believe that it happened gradually.
The landscape of Northern Europe was dominated by mammoth steppes and regular tundra home for a few reindeer hunters.
After it had come into contact with the World Ocean, it became a brackish ocean, as we also know it today. The Yoldia sea is named after the mussel Yoldia arctica. It was connected to the World Ocean through a strait that lay where the Swedish lakes and the Gøta River are today.
The Maglemose hunters of the Stone Age could benefit from an increasingly warmer climate. At the beginning of their period, the tundra had just been overgrown by an open and light birch forest with aspen, willow, rowan and pine.
When Scandinavia was freed from the weight of the ice masses, the land rose, the uplift cut off the future Baltic Sea's connection with the World Ocean, and it again became a freshwater lake, which is called Lake Ancylus after the freshwater snail, Ancylus fluviatilis. Lake Ancylus may have drained through Central Sweden at the Great Lakes.
In step with the increasingly milder climate, where the average summer temperature rose to 18-20℃ and the winter temperature only just reaching below freezing, the composition of the forest's trees also changed; the pine pushed the birch back, and the hazel, elm, oak, ash, alder, spruce and linden moved in.
At the end of the period of the Maglemose Hunters, around 7,200 BC, the climate in Western Europe had changed to the so-called Atlantic climate. It was a mild and humid coastal climate with summer temperatures 2-3℃ higher than today. The water level in the World Ocean rose, which resulted in the salty sea water after some time penetrating Lake Ancylus, and the water in the Baltic Sea basin became salty again. The new sea is called the Littorina Sea after the saltwater snail Littorina littorea. It took several hundred years before the salinity reached its maximum.
Plants such as the mistletoe and the subtropical water plant hornwort, as well as animals such as the curly-crested pelican and terrapin became widespread in Northern Europe. The land was covered by an impenetrable primeval forest. Photo original older Danish textbook.
Late Pleistocene lake in the West Siberian lowland. Uploaded to Research Gate by Jan Mangerud based on maps by Svendsen et al.
The melting of the Scandinavian ice sheet created the Baltic Ice Lake, which was the beginning of the Baltic Sea. It later became a saltwater sea with a connection to the World Ocean, but around 5,000 years before the present, the World Sea's access to the Baltic Sea had become so narrow that the salinity was reduced and the Baltic Sea became a brackish water sea, as we know it today.
Reconstruction of drainage conditions in central Eurasia in the Late Pleistocene. Photo originally Google Maps.
The large Swedish and Finnish lakes were all created by the melting ice sheet, as they were originally parts of both the Yoldia Sea and the fresh water Ancylussø. Also the Russian Lake Onega in Karelia and Lake Peipus between Russia and Estonia - to name just a few of the largest - were created by the shrinking Weichel ice sheet.
It has been established with certainty that one or more times during the late Pleistocene there has been a very large lake in the areas of the Western Siberian Lowland, which are drained by the rivers Ob and Yenisei, where the height above sea level only in a few places exceeds 150 m. Many carbon 14 tests from both river valleys have confirmed that the lake last existed between 22,000 and 12,300 BC (Arkhipov 1973). One must assume that the existence of the lake was due to the fact that the outlet of the Ob and Yenisei into the Arctic Ocean must have been blocked at this time, probably by ice.
Surface level in the Black Sea and Caspian Sea during the Late Pleistocene. Note that the Caspian Sea has been very rich in water precisely during the Bølling-Allerød warm period, when it can be expected that a lot of meltwater was created. Furthermore, the curve for the water level in the Caspian Sea shows a significant drop precisely at the same time as the short cold period between Bølling and Allerød. This suggests that the high water level was really created by inflowing meltwater from the north. By comparison with the diagram below, which shows the surface level of the World Ocean, we see that the Black Sea has almost always had a higher surface level, which indicates that it has been cut off from the World Ocean. Only about 10,000 years before the present, the World Ocean, the Black Sea and the Caspian Sea all have the same surface level, indicating that they may have all been connected vessels - Mechnikov National University Ukraine.
However, glaciers form from abundant precipitation in the form of snow, and it is surprising that glaciers could form in the Polar Sea so far away from the moisture and precipitation of the Gulf Stream. Also, the sea level at this time was quite low, so it should have been a pretty solid barrier.
The exact extent of such a large lake or lake system in Western Siberia has not yet been mapped. It is likely that it was supplied with water from the Ob and Yenisei springs in the mountains of central Siberia. Based on the existing topography in the area and the reconstructed depth of the lake, researchers have found it likely that it had drainage to the south to the Aral Sea and the Caspian Sea, perhaps through the Turgay valley.
Sea level variation in the World Ocean in the late Pleistocene and Holocene. From Wikipedia
The existence of such a large West Siberian lake also indicates that Lake Baikal may have had an outlet to the Black Sea through the world's longest river. The Yenisei springs from Baikal and at that time had an outlet to the great West Siberian lake. The lake apparently had a drain through the Turgay valley to the Aral Sea, which at this time may have had a connection to the Caspian Sea and the Black Sea and from there perhaps on to the Mediterranean with a large waterfall. Such a river would have been more than 10,000 km. long.
3. Floods in late Pleistocene
In Central Asia and North America, during the melting of the ice sheet in the late Pleistocene, several huge catastrophic floods occurred, caused by the dam collapse of giant lakes dammed by parts of glaciers in mountain valleys. The flod waves had such strength and scope that they bring to mind the Biblical flood.
Hubbard Glacier in Alaska. It is expected that after a few years it will have expanded again so that it will cut off Russell Fjord from Disenchantment Bay and the sea. The water level in Russel Fjord will rise again, and the ice dam will collapse again after some time.
The mechanism of the flood waves is illustrated quite well by the present-day situation of the Hubbard Glacier in Alaska.
Hubbard Glacier's ice edge advanced over a hundred years, and in May 1986 it pushed forward and blocked the outlet from Russell Fjord, creating "Russell Lake". All of the summer's meltwater ran into the new glacier-dammed lake and the water level rose by 25 metres.
Around midnight on October 8 of that year, the ice dam began to fail. In the next 24 hours, a flod wave of an estimated 5.3 km3 of water washed out through the dam breach and the fjord was reconnected to the sea. The volume of the flow was equivalent to 35 times Niagara Falls.
Kurai and Chuya were two late Pleistocene glacier-dammed lakes in the Altai Mountains along the Chuya River.
The Hubbard glacier is still advancing, and it can be predicted that in a few years it will again cut off Russell Fjord, the water level in the new lake will rise again until the ice dam collapses and a new flood wave will wash out to sea.
Similar glacier-dammed lakes existed in the late Pleistocene in the mountains of southern Siberia and in the Rocky Mountains of North America - but on a much larger scale.
Russian geologist Alexei N. Rudoy has explored traces of giant flood waves found in the Altai Mountains. He proposed the term diluvium for such changes in the landscape, which were caused by catastrophic flood waves from giant glacier-dammed lakes.
Ripple pattern at the bottom of a stream created by turbulent flow. Photo unknown origin.
Towards the end of the last ice age, some believe in the interval between 40 and 13 thousand years before the present, the glaciers of the Altai Mountains blocked the Chuya River, which is a tributary of the Katun, which in turn is a tributary of the Ob. The ice dams created at least two large glacial meltwater lakes in the Chuya and Kurai valleys. After some time the lakes became large and deep. Since ice is not a very durable dam material, the dams burst in chain reaction or individually, causing catastrophic floods that swept along the Chuya and Katun rivers. In the time interval mentioned above, there were at least five major floods. Also in the Uymon valley in Altai and the Darkhat lakes in Mongolia, glacier-dammed lakes existed in the late Pleistocene.
Landscape with a pattern from giant flood waves in the Altai mountains, which bears witness to a gigantic flood wave sometime in the past. Photo by Alexei Rudoy July 2011.
Based on the estimated volume of the original glacier-dammed lakes, which is estimated to just over 600 km3, height differences and cross-sections of the river valleys, some geologists have calculated some approximate water speeds of tens of meters per second. In a very short time, i.e. a few days, clearly less than a week, the original landscapes underwent enormous changes as a result of the late Pleistocene super flood waves.
Square river valleys along the Katun River in Altai, which bear witness to gigantic destructive flood waves in the past. Photo by Alexei Rudoy July 2011.
In the sandy bottom of streams and rivers, a wave pattern formed by the turbulent flow is often seen. The size and shape of the pattern depends on the speed and volume of the flow. In the Chuya and Katun valleys, Rudoy and his colleagues found areas with gigantic wave patterns, which testify to equally gigantic floods sometime in the past. The wave landscape is made up of round pebbles and the waves can be up to 18 m high and have wavelengths of 50 to 150 m.
Rivers, which over millennia have slowly worked their way into the landscape, typically create V-shaped river valleys, such as the Rhine and Danube river valleys. Glaciers create typical U-shaped river valleys. But dynamic and destructive food waves, which sweep away everything, create square valleys. In the Altai, the geologists found huge square river valleys, which bear witness to gigantic destructive flod waves in the late Pleistocene.
Common "Gravel bars" in the Toklat River in Alaska. Photo Q.T. Luong.
Fast-flowing rivers can form elongated banks of stones and gravel that they bring with them. They are called "gravel bars" in English. They are typically formed in the middle of the river or along one of the banks. In the Altai, Rudoy and his colleagues found very large "gravel bars", apparently deposited by huge, fast-flowing flood waves at the end of the Ice Age.
Such landscapes, formed by huge flood waves sometime in the past, are found in several places in Eurasia. In addition to the Altai Mountains, they have been found in both Tuva and Tibet.
Huge "gravel bar" in the central Altai, which testifies to a huge volume flow that took place in the past - photo by Alexei Rudoy July 2011.
Elizabeth Barber wrote in her book "The Mummies of Urumchi" that in the late Pleistocene the Tarim Basin was a large lake. Chinese sources (Feng, Q., Z. Su, and H. Jin), on the other hand, write: "The climate in the Tarim Basin has been persistently dry through alternating hot and cold periods. Consequently, the sedimentary environments have varied greatly between desert and steppe influenced by the encircling mountains and global climatic fluctuations." Other sources mention scattered forest combined with steppe. We must conclude that the climate in East Central Asia through the late Pleistocene was probably more fertile than today, but relatively dry, since the rainfall in Central Asia has not been sufficient to form the same extensive glaciers as in Scandinavia and North America.
Giant current-wave pattern at Washtucna Coulee in Washington state. Photo Glacial Lake Missoula.
Two types of giant catastrophic floods are known from North America, namely the Missoula flood wave and the Bonneville flood wave. The Missoula flood waves came from the glacier-dammed Missoula Lake and occurred many times at regular intervals. The Bonneville flood wave came from the moraine-dammed Bonneville Lake and occurred only once.
Lake Missoula was a large glacier-dammed lake in western Montana; it existed in the late Pleistocene in the period from 15,000 to 13,000 years before the present. It was created by a glacial blockage of the Clark Fork River. As with other glacier-dammed lakes, the ice dam broke at intervals and the lake emptied its water through the Clark Fork River valley. The Clark Fork River is a tributary of the Columbia River, which empties into the Pacific Ocean. The wave flooded large areas of eastern Washington state and the Willamette Valley in western Oregon. Geologist J. Harlen Bretz proposed that the characteristic landscape of Washington State, called the Channeled Scablands, was created by repeated massive floods over 2,000 years. Map from Parfit, "The Floods that Carved the West."
The path of the Missoula flood waves through Montana, Idaho and Washington. Lake Missoula is shown in blue, and the flooded areas, called Channeled Scablands, are shown in gray. Photo The Northwest Creation Network.
From the many shorelines found in the valleys of western Montana, some have calculated that Pleistocene Lake Missoula had a volume of about 2,200 km3.
Geologists estimate that the cycle of flooding and regeneration of the lake lasted an average of 55 years. Jim O'Connor and Gerard Benito of the US Geological Survey have found evidence of at least 25 massive floods. The largest flood wave is believed to have had a volume flow of about 10 km3 per hour, which is 13 times the volume flow of the Amazon River.
Lake Bonneville 14,500 years before present in the late Pleistocene. The Pleistocene lakes are shown in light blue. The modern Great Salt Lake is shown in dark blue. The flood wave broke through at Red Rock Pass and spread northward into Idaho and Oregon along the Snake River, until it reached the Scablands in Washington, whereupon it followed the path of the Missoula flood waves to the ocean along the Columbia River. Map Geology 101 Field Trip FT Main.
Bonneville Lake was a very large lake in the state of Utah. The lake existed in the late Pleistocene, 14,500 years ago. The Great Salt Lake is the last remnant of the giant lake. Unlike Missoula, Lake Bonneville was a type of moraine-dammed lake. The dam was created from gravel and rock that an Ice Age glacier may have dragged and deposited at the northern end of the lake in Red Rock Pass in southeastern Idaho.
Just under 15,000 years ago, the rock and gravel dam collapsed and Lake Bonneville poured immeasurable amounts of meltwater over Red Rock Pass and into the Snake River Basin, where it caused widespread flooding.
The elevation above sea level of Lake Bonneville's shorelines during eras of the lake's history - as explored by various geologists. The vertical scale on the left is m above sea level. The horizontal scale is years before present. It can be seen that Lake Bonneville's surface was about 1,540 m. above sea level. After the flood wave, the surface sank down to the Provo shoreline about 100 m. lower. This means that a volume of 100 m multiplied by the area of ??the lake was washed over Idaho and Washington. Estimates of the lake's area vary, but if it was around 51,300 km2, it would mean that the volume of the flood wave would have been just under 5,130 km3. Drawing Idaho State University.
From there the flood wave continued along the Snake river into Idaho and Oregon until the Columbia River valley in Washington and then out to sea. One can imagine that the breakthrough was first a small trickle of water, which developed into a destructive flood wave that swept everything away.
Large flood waves in the Quaternary after "The world's largest floods, past and present: their causes and magnitudes" by Jim E. O'Connor and John E. Costa. The volume flow under "Peak discharge" is given here in km3/hour.
Many calculations have been made on how fast the water flowed, but it is easy to realize that with a pressure head of 100 m. it has been a very destructive flood.
