Lake Allison was a temporary lake in the

Willamette Valley The Willamette Valley ( ) is a long valley in Oregon, in the Pacific Northwest region of the United States. The Willamette River flows the entire length of the valley and is surrounded by mountains on three sides: the Cascade Range to the east, ...

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

, formed periodically by 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 la ...

from 15,000 to 13,000 BC. The lake is the main cause of the rich and fertile soil that now characterizes the Willamette Valley.

History

Willamette Valley fertility, like the

Palouse The Palouse ( ) is a distinct geographic region of the northwestern United States, encompassing parts of north central Idaho, southeastern Washington, and, by some definitions, parts of northeast Oregon. It is a major agricultural area, primari ...

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel whe ...

, is in large part due to the largest freshwater flood scientifically documented in history. The ice floods started in

Lake Missoula 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 lake measured about and contained about of water, half the volume of Lake Mi ...

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Colu ...

12,000 to 15,000 years ago during the

Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological 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 finally confirmed i ...

and flowed down through eastern Washington, bringing fertile soil to the valley as it flowed out the

Columbia River Gorge The Columbia River Gorge is a canyon of the Columbia River in the Pacific Northwest of the United States. Up to deep, the canyon stretches for over as the river winds westward through the Cascade Range, forming the boundary between the state ...

. The narrows at

Kalama, Washington Kalama (kaw-law-maw) is a city in Cowlitz County, Washington, United States. It is part of the Longview, Washington Metropolitan Statistical Area. The population was 2,959 as of the 2020 census. Etymology James W. Phillips' ''Washington State ...

, restricted the flow of water, causing it to back up and flood the

to a depth of above sea level as far south as Eugene.''Cataclysms on the Columbia'', by John Elliott Allen and Marjorie Burns with Sam C. Sargent, 1986. Pages 175–189. The Willamette Valley had multiple floods during the last ice age, possibly reaching 100 floods separated by centuries, to depths of 300–400 feet.''Geology of Oregon'', by Elizabeth L. Orr, William N. Orr and Ewart M. Baldwin, 1964. Pages 211–214. If floodwaters descended on the valley today, in

Portland Portland most commonly refers to: * Portland, Oregon, the largest city in the state of Oregon, in the Pacific Northwest region of the United States * Portland, Maine, the largest city in the state of Maine, in the New England region of the northeas ...

(elevation , only the tops of the West Hills,

Mount Tabor Mount Tabor ( he, הר תבור) (Har Tavor) is located in Lower Galilee, Israel, at the eastern end of the Jezreel Valley, west of the Sea of Galilee. In the Hebrew Bible (Joshua, Judges), Mount Tabor is the site of the Battle of Mount Tabo ...

, Rocky Butte, Kelly Butte and Mount Scott would be visible, as would the

US Bancorp Tower The U.S. Bancorp Tower (also known as the Big Pink) is a 42-story, skyscraper in Portland, Oregon. It is the second tallest building in the city after Wells Fargo Center, and with its nearly office space, it is the largest in Oregon in terms o ...

and the Wells Fargo Center . Newberg’s elevation is above sea level,

Oregon City ) , image_skyline = McLoughlin House.jpg , imagesize = , image_caption = The McLoughlin House, est. 1845 , image_flag = , image_seal = Oregon City seal.png , image_map ...

, McMinnville , Salem , Corvallis and Eugene , likely rising above all of them. The lake eventually flowed out and drained, leaving of layered sedimentary soils throughout the Tualatin, Yamhill and Willamette valleys.

Name

Geologists named the lake after

Oregon State University Oregon State University (OSU) is a public land-grant, research university in Corvallis, Oregon. OSU offers more than 200 undergraduate-degree programs along with a variety of graduate and doctoral degrees. It has the 10th largest engineering col ...

geologist Ira S. Allison. Among other things, he was the first person to identify and correlate Willamette silt soil in 1953 with soils at the former lake bed of

Lake Lewis Lake Lewis was a temporary lake in the Pacific Northwest region of North America, largely formed by the Missoula Floods in about the 14th millennium B.C. Lake Lewis was formed when the restricted flow of waters from periodic cataclysmic floods f ...

in eastern Washington. In the 1930s he had documented hundreds of non-native boulders (also known as glacial erratics) that had been transported by the floods on

iceberg An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Smaller chunks of floating glacially-derived ice are called "growlers" or "bergy bits". The ...

s and had left a ring around the lower hills surrounding the Willamette Valley. The most notable of these is the Bellevue Erratic, off Highway 18 west of McMinnville.

References

External links

Missoula Floods information
- Columbia River Images
Most powerful documented freshwater flood in history
- Waymark {{authority control

Allison Allison may refer to: People * Allison (given name) * Allison (surname) (includes a list of people with this name) * Eugene Allison Smith (1922-1980), American politician and farmer Companies * Allison Engine Company, American aircraft engine ...

Willamette Valley Geology of Oregon

Willamette River

History

Name

See also

References

External links