Outburst flood
In
Definition and classification
Megafloods are
- Collapse of glacier dams that impound proglacial lakes (Missoula Floods).
- Rapid erosion, melting of ice sheets (jökulhlaups).
- Collapse of earthen barriers (landslides or glacial moraines).
- Collapse of volcanic dams created by lava flows, lahars, or pyroclastic flows.
- Overtopping of earthen or rock barriers
- Lake overtopping (e.g., Lake Bonneville).
- Ocean spilling over a dividing ridge into a landlocked basin (e.g., Zanclean flood and Black Sea flood).[1] A smaller scale example would be the Pantai Remis landslide.
Examples
Examples where evidence for large ancient water flows has been documented or is under scrutiny include:
Overflow of lakes formed by landslides
An example is the lake overflow that caused one of the worst landslide-related disasters in history on June 10, 1786. A landslide dam on Sichuan's
Postglacial rebound
Tectonic basins
The Black Sea (around 7,600 years ago)
A rising sea flood, the proposed and much-discussed refilling of the freshwater glacial Black Sea with water from the Aegean, has been described as "a violent rush of salt water into a depressed fresh-water lake in a single catastrophe that has been the inspiration for the flood mythology" (Ryan and Pitman, 1998). The marine incursion, caused by the rising level of the Mediterranean, apparently occurred around 7,600 years ago. It remains an active subject of debate among geologists, with subsequent evidence discovered to both support and refute the existence of the flood, while the theory that it is the basis of later flood myths is not proven.
Persian Gulf Flood (24,000 to 14,000 years ago, or 12000 to 10000 years ago)
Flooding of this area scattered peoples to both sides of the gulf depression. It was an area fed by four rivers. Rose calls it the "Gulf Oasis" which may have been a demographic refuge fed by the Tigris, Euphrates, Karun, and Wadi Batin rivers. It was suggested to be an area of freshwater springs and rivers.[6][7]
Glacial floods in North America (15,000 to 8,000 years ago)
In North America, during glacial maximum, there were no Great Lakes as we know them, but "proglacial" (ice-frontage) lakes formed and shifted. They lay in the areas of the modern lakes, but their drainage sometimes passed south, into the Mississippi system; sometimes into the Arctic, or east into the Atlantic. The most famous of these proglacial lakes was Lake Agassiz. As ice-dam configurations failed, a series of great floods were released from Lake Agassiz, resulting in massive pulses of freshwater added to the world's oceans.
The
The last of the North American proglacial lakes, north of the present Great Lakes, has been designated
The detailed timing and rates of change after the onset of melting of the great ice-sheets are subjects of continuing study.
The Caspian and Black Seas (around 16,000 years ago)
A theory proposed by Andrey Tchepalyga of the
Red Sea floods
The barrier across
English Channel floods
Originally there was an isthmus across the Strait of Dover. During an earlier glacial maximum, the exit from the North Sea was blocked to the north by an ice dam, and the water flowing out of rivers backed up into a vast lake with freshwater glacial melt on the bed of what is now the North Sea. A gently upfolding chalk ridge linking the Weald of Kent and Artois, perhaps some 30 metres (100 feet) higher than the current sea level, contained the glacial lake at the Strait of Dover. At some time, probably around 425,000 years ago and again around 225,000 years later the barrier failed[11] or was overtopped, loosing a catastrophic flood that permanently diverted the Rhine into the English Channel and replacing the "Isthmus of Dover" watershed by a much lower watershed running from East Anglia east then southeast to the Hook of Holland and (as at modern sea level) separated Britain from the continent of Europe; a sonar study of the sea bed of the English Channel published in Nature, July 2007,[12] revealed the discovery of unmistakable marks of a megaflood on the English Channel seabed: deeply eroded channels and braided features have left the remnants of streamlined islands among deeply gouged channels where the collapse occurred.[13][11]
The refilling of the Mediterranean Sea (5.3 million years ago)
A catastrophic flood refilled the Mediterranean Sea 5.3 million years ago, at the beginning of the
The Mediterranean did not dry out during the most recent glacial maximum. Sea level during glacial periods within the Pleistocene is estimated to have dropped only about 110 to 120 metres (361 to 394 ft).[16][17] In contrast, the depth of the Strait of Gibraltar where the Atlantic Ocean enters ranges between 300 and 900 metres (980 and 2,950 ft).[18]
See also
- Altai flood – Prehistoric event in Central Asia
- Dam failure – Catastrophic failure of dam barrier by uncontrolled release of water
- Flood myth – Motif in which a great flood destroys civilization
- Glacial lake outburst flood – Type of outburst flood that occurs when the dam containing a glacial lake fails
- Jökulhlaup – Type of glacial outburst flood
- Lake Atna – Prehistoric lake in Alaska, formerly of Alaska
- Lake Corcoran – Lake in the state of California, United States, formerly of California
- Missoula Floods – Heavy floods of the last ice age (Pleistocene– First epoch of the Quaternary Period megaflood)
- Lake Missoula– Prehistoric proglacial lake in Western Montana
- J Harlen Bretz – American geologist who discovered the Missoula Floods
- Outflow channels – Long, wide swathes of scoured ground on Mars
- Zanclean flood – Theoretical refilling of the Mediterranean Sea between the Miocene and Pliocene Epochs
- Great Flood (China) – Myth described in Chinese mythology
References
- ^ ISBN 978-0-521-86852-5.
- ISBN 978-0-415-27298-8.[page needed]
- ^ ISBN 978-0-521-86852-5.
- S2CID 249961353.
- ISBN 978-90-5809-393-6.
- S2CID 144935980.
- .
- ^ Gilbert, Karl Grove (1890). Lake Bonneville. Washington, D.C.: Government Printing Office.
- ^ Tchepalyga, Andrey (2003-11-04). "Late glacial great flood in the Black Sea and Caspian Sea (abstract)". Abstracts with Programs. The Geological Society of America 2003 Seattle Annual Meeting. Vol. 35–6. Seattle, Washington. p. 460. Archived from the original on 2007-06-14. Retrieved 2007-07-24.
- ISBN 0-19-507048-8
- ^ .
- S2CID 4408290.
- ^ BBC News, "Megaflood' made 'Island Britain'" Archived 2007-07-20 at the Wayback Machine
- S2CID 205218854.
- ISBN 978-0-691-08293-6.[page needed]
- .
- .
- ISBN 978-0-7923-2624-3.
External links
- Rudoy, Alexei N (January 2002). "Glacier-dammed lakes and geological work of glacial superfloods in the Late Pleistocene, Southern Siberia, Altai Mountains". Quaternary International. 87 (1): 119–40. .
- Catastrophic floods in the English Channel - Inundations
- Iturrizaga, Lasafam (2011). "Glacier Lake Outburst Floods". Encyclopedia of Snow, Ice and Glaciers. Encyclopedia of Earth Sciences Series. pp. 381–99. ISBN 978-90-481-2641-5.