Ice Age Floods cause mass extinctions?

During the last Ice Age (18,000 to 12,000 years ago), and in multiple previous Ice Ages, cataclysmic floods inundated portions of the Pacific Northwest from Glacial Lake Missoula, pluvial Lake Bonneville, and perhaps from subglacial outbursts. Glacial Lake Missoula was a body of water as large as some of the USA's Great Lakes. This lake formed from glacial meltwater that was dammed by a lobe of the Canadian ice sheet. Episodically, perhaps every 40 to 140 years, the waters of this huge lake forced its way past the ice dam, inundating parts of the Pacific Northwest. Eventually, the ice receded northward far enough that the dam did not reform, and the flooding episodes ceased.

It was in 1923 that J Harlen Bretz published the first in a series of scientific papers in which he proposed that the severely eroded Channeled Scabland, Dry Falls, and other immense geologic features had been formed by a huge, powerful flood that had swept through the Columbia Basin during the Ice Age.

Despite his peers’ doubt and opposition, he resolutely maintained that direct examination of the geologic evidence could lead only to that conclusion. But Bretz was unable to identify the source or cause of such catastrophic flooding.

Earlier, in 1910, another geologist, Joseph T. Pardee, had described evidence of a great ice dammed lake, Glacial Lake Missoula, that had formed during the Ice Age in northwestern Montana. However, Bretz didn't see the connection between the glacial lake in Montana and the features he described in Eastern Washington. Then, in 1940, Pardee reported on his discovery of giant ripple marks, 50 feet high and 200-500 feet apart, that had formed on the floor of Glacial Lake Missoula. These huge, current-related features, along with other newly-found landforms, dramatically confirmed that the lake had suddenly emptied to the west, unleashing the tremendously powerful erosive forces that shaped many of the landforms found in the Columbia Basin.

More research followed, and new perspectives became available from aerial photography. Among geologists, the concept of a catastrophic flood came to be accepted by the late 1950s.

Drumlins and subglacial meltwater floods.

Since 1983, several investigators have developed a theory of drumlin formation by catastrophic flooding due to the release of meltwater that is believed to have accumulated beneath melting ice sheets. The proposed catastrophic sheet floods, as wide as the drumlin fields, formed the drumlins and related streamlined landforms, such as flutings, over wide areas. So-called rogen moraine, consisting of transverse ridges of drift, often found associated with drumlins, is reinterpreted in the meltwater flood hypothesis as possible giant current ripples.

Homework? You've got papers on the scablands, history of mainstream geological thoughts, and the "recent" synthesis of the available evidence for large, repetitive, localized flood events; how are you getting from local flooding to mass extinction?

Web definitions for Mass extinction:

The name given to a period of especially high rates of extinction of species. Several such events are seen in the fossil record.

palaeo.gly.bris.ac.uk/communication/boulton/glossary.html

- Definition in context

How do we define a Mass Extinction? Traditionally, within geological sciences, mass extinctions have been seen as some type of catastrophe for the world's biota. There have been many, long-term discussions about the importance of such catastrophes during earth history, and especially about their importance for long-term evolution. In Darwin's time (1850-1860s) the view that catastrophes were an integral part of evolution was frowned upon, and seen as a fall-back to ancient theories of catastrophism, as exemplified by the description of Noah's flood in the Bible. This view has changed recently, and modern ideas of catastrophism are part of an active discussion of 'internal' and 'external' causes of evolution. Internal causes meaning causes internal to the biota (such as competition, evolution of diseases), external meaning causes external to the biota (such as volcanic eruptions or nuclear war).

Yes, if it looks like homework, the forum policy is that the question go into the "Homework Help" area, and that the poster demonstrate effort toward answering the question.

Again, how do you propose to connect local flooding events to extinction events?

Hills point to catastrophic Ice Age floods

Fields of low hills that cover parts of inland Canada and the northern United States may seem quite distant from the watery world of Atlantis. Yet a Canadian geologist proposes these hills formed from huge Ice Age floods that sharply raised global sea levels and could have spawned myths of a swamped continent.

"There's nothing in recorded history that matches the size of these floods," says John Shaw of Queen's University in Kingston, Ontario, who has estimated the extent of the floods from the size of the ridges.

Called drumlins--a word derived from Old Irish -- these hills appear in concentrated fields in North America, Scandinavia, Britain and other areas once covered by ice. When seen from above, the aligned knolls sometimes look like a basket of eggs lying on their sides and pointing in the same direction. Some drumlins are made of sediments deposited onto bedrock; others are ridges carved out of the rock.

Most geologists believe drumlins developed gradually from the grinding action of heavy ice sheets as they moved over the land. But in the last several years, Shaw and others have proposed the controversial idea that floods of water flowing beneath the ice created many of the North American drumlins and possibly others around the world. They base this hypothesis on the shapes drumlins share with other land forms sculpted by meltwater.

Himalayan Ice Dams Created Huge Lakes, Floods

Environment News Service, December, 2004

SEATTLE, Washington (ENS) — --> Ice dams across the deepest gorge on Earth created some of the highest elevation lakes in history, according to new research from University of Washington geologist David Montgomery, a professor of Earth and space sciences.

The most recent of these lakes, in the Himalaya Mountains of Tibet, broke through its ice barrier somewhere between 600 and 900 AD, causing massive torrents of water to pour through the Himalayas into India, Montgomery said.

Geological evidence points to the existence of at least three lakes, and probably four, at various times in history when glacial ice from the Himalayas blocked the flow of the Tsangpo River in Tibet, he said .

The Baltic Sea, with its unique brackish water, is a result of meltwater from the Weichsel glaciation combining with saltwater from the North Sea when the straits between Sweden and Denmark opened. Initially, when the ice began melting about 10,300 ybp, seawater filled the isostatically depressed area, a temporary marine incursion that geologists dub the Yoldia Sea. Then as post-glacial isostatic rebound lifted the region about 9500 ybp, the deepest basin of the Baltic became a freshwater lake, in palaeological contexts referred to as Ancylus lake, which is identifiable in the freshwater fauna found in sediment cores. The lake was filled by glacial runoff, but as worldwide sea level continued rising, saltwater again breached the sill about 8000 ybp, forming a marine Littorina Sea which was followed by another freshwater phase before the present brackish marine system was established. "At its present state of development, the marine life of the Baltic Sea is less than about 4000 years old," Drs Thulin and Andrushaitis remarked when reviewing these sequences in 2003.
Overlaying ice had exerted pressure on the earth's surface. As a result of melting ice, the land has continued to rise yearly in Scandinavia, mostly in northern Sweden and Finland where the land is rising at a rate of as much as 8-9 mm per year, or 1 meters in 100 years. This is important for archeologists since a village that was coastal in the Nordic Stone Age now is inland.

Evidence shows that the on slaught of Ice Age floods was not so localized:

This type of study is relatively new and so not many sites have been thoroughly surveyed. My question is more about if anyone has further evidence of these floods around the world and if this type of catastrophic event could have contributed to the demise of mega fauna in north america, siberia and mongolia or related areas.

Just asking for a little help here. Plus, its a fascinating study, don't you agree?!

There might be an interconnection between all those "floods" and extinctions but it's probably a lot more complicated.

The late Pleistocene megafauna extinction started around 14000 calendar years ago with horses in Alaska and woolly rhinos in Eurasia and it ended probably 4150 Calendar years ago with the last population of woolly mammoths on Wrangel island.

The Alaskan horses decreased notably in size during their last few milleniums of existance and this is also true for most woolly mammoth populations. Furthermore, together with extinction of the horses was a strong population explosion from modern megafauna like elk and bison. There is also distinct evidence of biotope change from dry steppe to wood-lands. No signs of floods there as far I know.

The bulk of the extinction appeared to have been around the end of the Younger Dryas between 11,500 and 10,500 years but the giant (irish) Elk survived until some 6000 years ago. There may be a case for the Americal mastodons as well having survived to a few milleniums ago.

Not only Eurasia and North America but the extinction took also place in South America, mostly giant sloths, mastodon and Gomphotherium (four tusked elephants).

Now it could be that many factors contributed to the extinctions, however if such contribution is dispensable, it's not the common cause. Humans may have killed some, even a lot of megafauna but certainly not all. Floods may have flushed away many specimens. Diseases may have decimated weakened hurds. But the common denominator for all extinctions appears to be change in habitat and consequently the loss of the battle for survival.

The changes in habitat appear to have one comemon cause: climate changes. Those were there all the time.

See also:

http://www.physicsforums.com/showthread.php?t=127240

http://www.physicsforums.com/showthread.php?t=126676

Each event is local. Did flood events take place over a large area of the world? Sure, but not simultaneously.

(snip)


The debate between "catastrophism" and "uniformitarianism" has moved to the middle ground of "both." There are little catastrophes (local) and global catastrophes --- you need something on a global scale to rationalize mass extinction events, and sporadic collapses of ice dams on meltwater lakes don't really fit into that category. Yes, local populations of this, that, or the other can be wiped out, and surviving populations from elsewhere expand into the cleared area to be wiped out during the next event. Wipe out every population everywhere at one time? No.

It was a mistake for me to include the extinction possiblity with this thread. I wish I could edit my title. The Ice Age Flood analytical studies are facsinating enough with out the idea of a bunch of drowning mammoths. Thank you for at least reading some of what I've written here.