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Glacial Lake Columbia (west) and Glacial Lake Missoula (east) are shown south of Cordilleran Ice Sheet. The areas inundated in the Columbia and Missoula floods are shown in red.

During the Ice Age Floods, Dry Falls was under 300 feet of water approaching at a speed of 65 miles per hour.

The Missoula Floods (also known as the Spokane Floods or the Bretz Floods) refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. The glacial flood events have been researched since the 1920's. These glacial lake outburst floods were the result of periodic sudden ruptures of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each ice dam rupture, the waters of the lake would rush down the Clark Fork and the Columbia River, inundating much of eastern Washington and the Willamette Valley in western Oregon. After the rupture, the ice would reform, recreating Glacial Lake Missoula once again. Geologists^[who?] estimate that the cycle of flooding and reformation of the lake lasted an average of 55 years and that the floods occurred approximately 60 times over the 2,000-year period between 15,000 and 13,000 years ago. The peak flow of the largest floods is estimated to be 40 to 60 cubic kilometers per hour.^[1] Glacial Lake Columbia (west) and Glacial Lake Missoula (east) are shown in blue, south of the Cordilleran Ice Sheet. ... Glacial Lake Columbia (west) and Glacial Lake Missoula (east) are shown in blue, south of the Cordilleran Ice Sheet. ... In Central Washington at the opposite side of the Grand Coulee from the Columbia River resides a three and a half mile crescent shaped precipice known as Dry Falls. ... Flooding near Key West, Florida, United States from Hurricane Wilmas storm surge in October 2005 For other uses, see Flood (disambiguation). ... For the capital city of the United States, see Washington, D.C.. For other uses, see Washington (disambiguation). ... The Columbia River Gorge is a spectacular canyon of the Columbia River in the Pacific Northwest of the United States. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Hubbard Glacier, Alaska squeezes towards Gibert Point on May 20, 2002. ... The Clark Fork River is a river in the U.S. states of Montana and Idaho, approximately 360 mi (579 km) long. ... Glacial Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. ... The Columbia River (French: fleuve Columbia) is a river in the Pacific Northwest region of North America. ... The Willamette Valley The Willamette Valley The Willamette Valley is the region in northwest Oregon in the United States that surrounds the Willamette River as it proceeds northward from its emergence from mountains near Eugene to its confluence with the Columbia River. ... This article is about the U.S. state. ...

History of their research

Geologist J Harlen Bretz first recognized evidence of the catastrophic floods, which he called the Spokane Floods, in the 1920s. He was researching the Channeled scablands in Eastern Washington, the Columbia Gorge and the Willamette Valley of Oregon. Bretz, however was not able to explain the source of the huge volume of water and his hypothesis was controversial, partly due to the popularity at that time of the principle of uniformitarianism in geologic processes. The Geologist by Carl Spitzweg A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth and planets of the solar system (see planetary geology). ... J Harlen Bretz (1882 - 1981) was an American geologist, best known for his research that led to the acceptance of the Missoula Floods. ... DrumHeller Channels The Channeled Scablands are unique geological erosion features in the U.S. state of Washington. ... For the university, see Eastern Washington University. ... The Columbia River Gorge is a spectacular canyon of the Columbia River in the Pacific Northwest of the United States. ... The Willamette Valley The Willamette Valley The Willamette Valley is the region in northwest Oregon in the United States that surrounds the Willamette River as it proceeds northward from its emergence from mountains near Eugene to its confluence with the Columbia River. ... This article is about the U.S. state. ... Uniformitarianism, in the philosophy of science, is the assumption that the natural processes operating in the past are the same as those that can be observed operating in the present. ...

In 1925 another geologist, Joseph Pardee, suggested that the water came from the failure of the glacial dam holding back the waters of Lake Missoula. By studying the canyon of the Flathead River, he estimated that flood waters in excess of 45 miles per hour would be required to roll the largest of the boulders moved by the flood. He estimated the water flow was nine cubic miles per hour, more than the combined flow of every river in the world.^[2] Some estimates^[who?] place the flow at ten times the flow of all current rivers combined. Joseph T. Pardee was a U.S. geologist who worked for the U.S. Geological Survey, and contributed to the understanding of the origin of the Channeled scablands. ... The Flathead River is a tributary of Clark Fork in the U.S. state of Montana and the Canadian province of British Columbia. ...

Further research^[who?] confirmed this hypothesis and the cause of the floods was finally explained. The Missoula Floods are also called the Bretz Floods in honor of Bretz.

Flood creation

The mechanism by which the ice dam failed was as follows. Under pressure, the melting point of water decreases. As the depth of the water in Lake Missoula increased, the pressure at the bottom increased enough to lower the freezing point of water below the temperature of the ice forming the dam. This allowed liquid water to seep into minuscule cracks present in the ice dam. Over a period of time, the friction from water flowing through these cracks generated enough heat to melt the ice walls and enlarge the cracks. This allowed more water to flow through the cracks, generating more heat, allowing even more water to flow through the cracks. This feedback cycle eventually weakened the ice dam so much that it could no longer support the pressure of the water behind it, and it failed catastrophically. This same process triggered a similar event in Iceland on November 5, 1996. is the 309th day of the year (310th in leap years) in the Gregorian calendar. ... Year 1996 (MCMXCVI) was a leap year starting on Monday (link will display full 1996 Gregorian calendar). ...

Frequency

Geologists estimate that the cycle of flooding and reformation of the lake lasted on average of 55 years and that the floods occurred approximately 60 times over the 2,000-year period between 15,000 and 13,000 years ago.

As the water emerged from the Columbia River gorge, it backed up again at the 1 mile (1.6 km) wide narrows near Kalama, Washington. Some temporary lakes rose to an elevation of more than 400 ft (120 m), flooding the Willamette Valley to Eugene, Oregon and beyond. Iceberg rafted glacial erratics and erosion features are evidence of these events. Lake-bottom sediments deposited by the Missoula Floods are the primary reason for the agricultural richness of the Willamette Valley. Kalama is a city located in Cowlitz County, Washington. ... Nickname: Motto: The Worlds Greatest City of the Arts & Outdoors Coordinates: , Country State County Lane Founded 1846 Incorporated 1862 Government  - Mayor Kitty Piercy Area  - City 40. ... A Glacial erratic is a piece of rock carried by glacial ice some distance from the rock outcrop from which it came. ...

Peak flow during floods

The peak flow of the largest floods is estimated to be 40 to 60 cubic kilometers per hour (9.5 to 15 cubic miles per hour).^[1][3] The maximum flow speed approached 36 meters/second (130 km/h; 80 miles per hour).^[4] Up to 1.9×10¹⁹ joules of potential energy were released by each flood, the equivalent of 4500 megatons of TNT.^[5] The cumulative effect of the floods was to excavate 210 km³ (50 cu mi) of loess, sediment and basalt from the channeled scablands of eastern Washington and to transport it downstream.^[1] Unit of energy commonly used to quantify laerge amounts of energy. ... A cubic kilometre (symbol km³) is an SI derived unit of volume. ... A cubic mile is an Imperial unit/U.S. customary unit (non-SI non-metric) of volume, used in the United States. ... DrumHeller Channels The Channeled Scablands are unique geological erosion features in the U.S. state of Washington. ...

References

Year 1923 (MCMXXIII) was a common year starting on Monday (link will display the full calendar) of the Gregorian calendar. ... Year 1925 (MCMXXV) was a common year starting on Thursday (link will display the full calendar) of the Gregorian calendar. ...

External links

• PBS's NOVA (TV series): Mystery of the Megaflood
• Ice Age Floods Institute
• University of Wisconsin overview of the Missoula Floods and their impacts.
• Dietrich, William. "Trailing an Apocalypse", Seattle Times – Pacific Northwest magazine, 2007-09-30. 
• The channeled scabland: a guide to the geomorphology of the Columbia Basin, Washington : prepared for the Comparative Planetary Geology Field Conference held in the Columbia Basin, June 5-8, 1978 / sponsored by Planetary Geology Program, Office of Space Science, National Aeronautics and Space Administration ; edited by Victor R. Baker and Dag Nummedal.

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