![Устье Чуи](https://upload.wikimedia.org/wikipedia/commons/a/a1/%D0%A3%D1%81%D1%82%D1%8C%D0%B5_%D0%A7%D1%83%D0%B8.jpg)
The Altai flood refers to the cataclysmic
flood
A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...
(s) that, according to some geomorphologists, swept along the
Katun River
The Katun (, ''Katuń''; , ''Kadın'') is a river in the Altai Republic and the Altai Krai of Russia. It forms the Ob as it joins the Biya some southwest of Biysk. in the
Altai Republic
The Altai Republic (; russian: Респу́блика Алта́й, Respublika Altay, ; Altai: , ''Altay Respublika''), also known as Gorno-Altai Republic, and colloquially, and primarily referred to in Russian to distinguish from the neighbour ...
at the end of the last
ice age
An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...
. These
glacial lake outburst flood
A glacial lake outburst flood (GLOF) is a type of outburst flood caused by the failure of a dam containing a glacial lake. An event similar to a GLOF, where a body of water contained by a glacier melts or overflows the glacier, is called a jö ...
s were the result of periodic sudden ruptures of ice dams like those triggering the
Missoula floods
The Missoula floods (also known as the Spokane floods or the Bretz floods or Bretz's floods) were cataclysmic glacial lake outburst floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ...
.
Background
In the USA, large glacial
outburst flood
In geomorphology, an outburst flood—a type of megaflood—is a high-magnitude, low-frequency catastrophic flood involving the sudden release of a large quantity of water. During the last deglaciation, numerous glacial lake outburst floods were ca ...
s have been researched since the 1920s. In the 1980s, Russian geologist
Alexei N. Rudoy proposed the term ''diluvium'' for deposits created as a result of
catastrophic outbursts of
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
giant glacier-dammed lakes in intermontane basins of the Altai. The largest of these lakes (the conjoined Chuya and Kuray) had a water volume of hundreds of cubic kilometers.
Evidence
Gravel ripples
Giant current ripples (gravel wave trains, diluvial dunes and
antidune
An antidune is a bedform found in fluvial and other channeled environments. Antidunes occur in supercritical flow, meaning that the Froude number is greater than 1.0 or the flow velocity exceeds the wave velocity; this is also known as upper flo ...
s) up to 18 meters high and 225 meters in wavelength were created in several locations along the lake bottom. They are best developed just east of the Tyetyo River in the eastern part of the Kuray Basin, but several other smaller fields of giant current ripples also occur there. They are made up of rounded pebble gravel.
Giant bars
Giant bars are found along the lower
Chuya
The Chuya (russian: Чуя; alt, Чуй, ''Çuy'') is a river in the Altai Republic in Russia, a right tributary of the Katun ( Ob's basin). The Chuya is long, and its drainage basin
A drainage basin is an area of land where all flowing ...
and the
Katun
Katun may refer to:
Places
* Katun (river), a tributary of the Ob in Siberia, Russia
* Katun Mountains or Katun Alps, a mountain range in Russia, part of the Altai Mountains
* Katun (Vranje), a village in Vranje Municipality, Serbia
* Katun (A ...
rivers, rising as much as 300m above modern river levels, with lengths up to five kilometers. Well-developed on the Katun River below its confluence with the Chuya River, the bars appear to have formed like giant point bars on the inner bends of the river, as opposed to the scoured bare bedrock walls of the ‘cut bank’ on the outer bends. These bars diminish in height and thickness downstream to about 60 m near Gorno-Altaisk.
![Lake formed behind gravel bar](https://upload.wikimedia.org/wikipedia/commons/0/0d/Lake_formed_behind_gravel_bar.jpg)
Some of these bars form lakes when blocking small tributaries of the Katun.
Suspension gravels
![Suspension gravel deposits](https://upload.wikimedia.org/wikipedia/commons/1/1b/Suspension_gravel_deposits.jpg)
Much of the gravel deposited along the Katun valley lacks a stratigraphic structure, showing characteristics of a deposition directly after suspension in a turbulent flow.
Large blocks
Unique block deposits
diluvial bermsof Rudoy) cap erosional terraces that are a few kilometers long, tens of
meters wide, and about 4 m above the lower bars. Block sizes range up to 20 m on the long axis, and show no
evidence of rounding
ig. 31 IG, Ig, or ig may refer to:
Companies
* IG Farben, a former German industrial conglomerate
* IG Group, a UK financial services company
* IG Recordings, a record label formed by the Indigo Girls, an American folk/rock duo
* Production I.G, a Japane ...
Cuspate erosional hollows
and accumulation ridges are associated with individual
blocks. Rudoy
003, pers. comm.estimates the discharge
required to transport these blocks in suspension was about 1
million m
3, with a duration of maximum flow of about 10
minutes.
Ice-rafted blocks
Ice-rafted boulders up to several meters in diameter.
Eddy deposits
![Outlet of the Chuya Basin](https://upload.wikimedia.org/wikipedia/commons/c/ce/Outlet_of_the_Chuya_Basin.jpg)
Eddy deposits are seen along the Katun River between Inya and Mali Yaloman.
Multiple flood hypothesis
Dating of the gravel bars has yielded at least 3 times of deposition, suggesting that multiple floods occurred.
The current understanding
![Lake deposits in Chuya Basin](https://upload.wikimedia.org/wikipedia/commons/b/bb/Lake_deposits_in_Chuya_Basin.jpg)
Towards the end of the last glacial period, 12,000 to 15,000 years ago, glaciers descending from the Altai mountains dammed the Chuya River, a large tributary of the Katun River, creating a large glacial lake including the Chuya and the Kurai basins. As the lake grew larger and deeper, the ice dam eventually failed, causing a catastrophic flood that spilled along the Katun River. This flood may have been the greatest discharge of freshwater on Earth, since its magnitude has been estimated similar to that of the
Missoula flood
The Missoula floods (also known as the Spokane floods or the Bretz floods or Bretz's floods) were cataclysmic glacial lake outburst floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ...
in
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
.
Timing
The age
of catastrophic flooding is not tightly constrained, and may involve several events. The mechanisms of lake filling and ice dam failure would suggest an early or late glacial time, whereas conditions at glacial maxima would seem to preclude such events. The catastrophic flood(s) occurred between 12000 BC and 9000 BC.
Most of the water discharge is thought to have occurred during one day, with peak discharges of 10
7 m
3/s (Herget, 2005). The maximum lake volume was 6x10
11 m
3 (600 km
3) with an area of 1.5x10
9 m
2. The ice dam was about 650 m high.
Flood route
When the ice dam failed, floodwaters coursed down the
Chuya
The Chuya (russian: Чуя; alt, Чуй, ''Çuy'') is a river in the Altai Republic in Russia, a right tributary of the Katun ( Ob's basin). The Chuya is long, and its drainage basin
A drainage basin is an area of land where all flowing ...
River to the confluence with the Katun River, followed the Katun into the Ob River, and then into
Lake Mansi
The West Siberian Glacial Lake, also known as West Siberian Lake (russian: Западно-Сибирское море) or Mansiyskoe Lake (russian: Мансийское озеро), was a periglacial lake formed when the Arctic Ocean outlets for ...
, a large proglacial Pleistocene lake, ~600,000 km
2 in area. The fast inflow raised its level by only ~12 m but some authors argue that, because the Turgay spillway of Lake Mansi was only 8 m above the lake level at the time, much of the floodwater continued into the
Aral Sea
The Aral Sea ( ; kk, Арал теңізі, Aral teñızı; uz, Орол денгизи, Orol dengizi; kaa, Арал теңизи, Aral teńizi; russian: Аральское море, Aral'skoye more) was an endorheic basin, endorheic lake lyi ...
. From there the flooding waters may have followed through the Uzboy spillway into the
Caspian Sea
The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad steppe of Central Asia ...
, then through the Manych spillway into the
Black Sea
The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Roma ...
, and eventually into the
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...
.
[Grosswald, M.G., 1998, New approach to the ice age paleohydrology of northern Eurasia. Chapter 15. (P. 199-214)— Palaeohydrology and Environmental Change / Eds: G. Benito, V.R. Baker, K.J. Gregory. — Chichester: John Wiley & Sons Ltd, 1998. 353 p.]
See also
*
*
*
*
References
External links
Lee, 2004, The Altay FloodAlexei N. Rudoy, 2005. Giant current ripples (History of the Research, their diagnostics and palaeogeographical significance). - Tomsk. - 224 pp. In Russian, Eng. summary: pp. 134-211 pp.{{Webarchive, url=https://web.archive.org/web/20171008181456/http://ice.tsu.ru/index.php?option=com_content&view=article&id=385%3A-q-q-2005-&catid=17%3A2011-02-24-10-44-05&Itemid=48 , date=2017-10-08
Geology of Asia
Megafloods