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
Dadu River, created by an earthquake ten days earlier, burst and caused a flood that extended downstream and killed 100,000 people.
Postglacial rebound Postglacial rebound changes the tilt of ground. In lakes, this means that shores sink in the direction farther away from the former maximum depth of ice. When the lake rests against an
esker, water pressure increases with the increased depth. The esker may then fail under the load and burst, creating a new outflow.
Lake Pielinen in Finland is an example of this.
Tectonic basins Black Sea (around 7,600 years ago) (dark blue) according to Ryan's and Pitman's theories 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 12,000 to 10,000 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 al-Batin rivers. It was suggested to be an area of freshwater springs and rivers.
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
Missoula Floods of
Oregon and
Washington states were also caused by breaking ice dams, resulting in the
Channeled Scablands.
Lake Bonneville, a
pluvial lake, burst catastrophically in the
Bonneville Flood about 14,500 years ago, due to its water overflowing and washing away a sill composed of two opposing
alluvial fans which had blocked a
gorge. Lake Bonneville was not a glacial lake, but glacial age climate change determined the lake level and its overflow. The first scientific report of a megaflood (Gilbert, 1890) describes this event. The last of the North American proglacial lakes, north of the present Great Lakes, has been designated
Glacial Lake Ojibway by geologists. It reached its largest volume around 8,500 years ago, when joined with Lake Agassiz. But its outlet was blocked by the great wall of the glaciers and it drained by tributaries, into the
Ottawa and
St. Lawrence Rivers far to the south. About 8,300 to 7,700 years ago, the melting ice dam over
Hudson Bay's southernmost extension narrowed to the point where pressure and its buoyancy lifted it free, and the ice-dam failed catastrophically. Lake Ojibway's beach terraces show that it was above sea level. The volume of Lake Ojibway is commonly estimated to have been about , more than enough water to cover a flattened-out Antarctica with a sheet of water deep. That volume was added to the world's oceans in a matter of months. 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
Russian Academy of Sciences dates the flooding of the Black Sea basin to an earlier time and from a different cause. According to Tchepalyga,
global warming beginning from about 16,000 BP caused the melting of the
Scandinavia Ice Sheet, resulting in massive river discharge that flowed into the
Caspian Sea, raising it to as much as above normal present-day levels. The
Sea of Azov rose so high that it overflowed into the Caspian Sea. The rise was extremely rapid and the Caspian basin could not contain all the floodwater, which flowed from the northwest coastline of the Caspian Sea, through the
Kuma-Manych Depression and
Kerch Strait into the Black Sea basin. By the end of the Pleistocene this would have raised the level of the Black Sea by some below its present-day level, flooding large areas that were formerly available for settlement or hunting. Tchepalyga suggests this may have formed the basis for legends of the great
Deluge.
Red Sea floods The barrier across
Bab-el-Mandeb, between Ethiopia and Yemen, seems to have been the source of outbreak flooding similar to that found in the Mediterranean. The
Lake Toba event, approximately between 69,000 and 77,000 years ago, caused a massive drop in sea levels, exposing the barrier and enabling modern
Homo sapiens to leave Africa via a route other than Sinai. The finding of saline
evaporites on the floor of the Red Sea confirms that this dam has functioned at various periods in the past. Rising sea levels during the
Flandrian transgression (and in earlier
interglacial periods) suggest that this area may have been subject to outburst flooding.
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 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, 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. The flood occurred when Atlantic waters found their way through the
Strait of Gibraltar into the desiccated
Mediterranean basin, following the Messinian salinity crisis during which it repeatedly became dry and re-flooded, dated by consensus to before the emergence of modern humans. 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). In contrast, the depth of the
Strait of Gibraltar where the Atlantic Ocean enters ranges between . ==See also==