Altai flood
Encyclopedia
The Altai flood refers to the cataclysmic flood
(s) that swept along the Katun River in the Republic of Altai at the end of the last ice age
. These glacial lake outburst flood
s were the result of periodic sudden ruptures of ice dams like those triggering the Missoula flood.
of Pleistocene
giant glacier-dammed lakes in intermontane basins of the Altai. The largest of these lakes (Chuya and Kuray) had a water volume of hundreds of cubic kilometers.
and the Katun River, to 300 m 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.
Some of these bars form lakes when blocking small tributaries of the Katun.
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 [Fig. 31]. Cuspate erosional hollows
and accumulation ridges are associated with individual
blocks. Rudoy [2003, pers. comm.] estimates the discharge
required to transport these blocks in suspension was about 1
million cms, with a duration of maximum flow of about 10
minutes.
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 in North America
.
Most of the water discharge is thought to have occurred during 1 day, with peak discharges of 1e7 m3/s (Herget, 2005). The maximum lake volume was 6e11 m3 wwith an area of 1.5e9 2m. The ice dam was about 650 m high.
to the confluence with the Katun River, followed the Katun into the Ob River, and then into Lake Mansi, a large proglacial Pleistocene lake, ~600,000 km2 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
. From there the flooding waters may have followed through the Uzboy spillway into the Caspian Sea
, then through the Maryinsky spillway into the Black Sea
, and eventually into the Mediterranean Sea
.
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
(s) that swept along the Katun River in the Republic of Altai at the end of the last ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
. These glacial lake outburst flood
Glacial lake outburst flood
A glacial lake outburst flood is a type of outburst flood that occurs when the dam containing a glacial lake fails. The dam can consist of glacier ice or a terminal moraine...
s were the result of periodic sudden ruptures of ice dams like those triggering the Missoula flood.
Background
Large glacial outburst floods have been researched since the 1920s in USA only . In the 1980s, Russian geologist Alexei N. Rudoy proposed the term diluvium for deposits created as a result of catastrophic outburstsGlacial lake outburst flood
A glacial lake outburst flood is a type of outburst flood that occurs when the dam containing a glacial lake fails. The dam can consist of glacier ice or a terminal moraine...
of Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
giant glacier-dammed lakes in intermontane basins of the Altai. The largest of these lakes (Chuya and Kuray) had a water volume of hundreds of cubic kilometers.
Gravel ripples
Giant current ripples (gravel wave trains, diluvial dunes and antidunes) were created at several places on the lake bottom. Ripples are up to 18 m in altitude and 225 m in wavelength. They best developed just east of the Tyetyo River in the eastern part of the Chuya lake. Several other smaller fields of giant current ripples occur in the Kuray Basin. The giant current ripples are composed of rounded pebble gravel.Giant bars
Giant bars found along the lower Chuya RiverChuya River
The Chuya River is a river in the Altai Republic in Russia, a right tributary of the Katun River . The Chuya is 320 km long, the area of its drainage basin is 11,200 km². The river freezes up in October - early November and breaks up in late April....
and the Katun River, to 300 m 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.
Some of these bars form lakes when blocking small tributaries of the Katun.
Suspension gravels
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 berms of Rudoy) cap erosional terraces that are a few kilometers long, tens ofmeters 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 [Fig. 31]. Cuspate erosional hollows
and accumulation ridges are associated with individual
blocks. Rudoy [2003, pers. comm.] estimates the discharge
required to transport these blocks in suspension was about 1
million cms, with a duration of maximum flow of about 10
minutes.
Eddy deposits
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
Towards the end of the last glacial period, 12,000 to 15,000 years ago, glaciers descending from the Altai mountains dammedthe Chuya River
Chuya River
The Chuya River is a river in the Altai Republic in Russia, a right tributary of the Katun River . The Chuya is 320 km long, the area of its drainage basin is 11,200 km². The river freezes up in October - early November and breaks up in late April....
, 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 in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
.
Timing
The age[s] 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 betwee 14 Ka and 11 Ka.Most of the water discharge is thought to have occurred during 1 day, with peak discharges of 1e7 m3/s (Herget, 2005). The maximum lake volume was 6e11 m3 wwith an area of 1.5e9 2m. The ice dam was about 650 m high.
Flood Route
When the ice dam failed, floodwaters coursed down the Chuya RiverChuya River
The Chuya River is a river in the Altai Republic in Russia, a right tributary of the Katun River . The Chuya is 320 km long, the area of its drainage basin is 11,200 km². The river freezes up in October - early November and breaks up in late April....
to the confluence with the Katun River, followed the Katun into the Ob River, and then into Lake Mansi, a large proglacial Pleistocene lake, ~600,000 km2 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
Aral Sea
The Aral Sea was a lake that lay between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south...
. From there the flooding waters may have followed through the Uzboy spillway into the Caspian Sea
Caspian Sea
The Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. The sea has a surface area of and a volume of...
, then through the Maryinsky spillway into the Black Sea
Black Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
, and eventually into the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
.