Yhdysvaltain luoteisosan geologinen kehitys ja Columbia-joen altaan suuret luonnonkatastrofit. (Geological evolution of the northwestern United States and catastrophic events in the Columbia River Basin)

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Description :
During the last glaciation the Cordilleran Ice Sheet covered the upper course of the Columbia River and part of the Columbia Plateau. A large ice-dammed lake called Glacial Lake Missoula was formed in Montana, when an ice lobe plugged a valley in Idaho. Once the water level in the ice lake had risen to a certain height the ice dam collapsed and draining of the ice lake resulted in a gigantic flood. A new ice dam was then formed, and after some time a further catastrophic flood occurred. It has been concluded that this cycle recurred about 40 times in a period approx. 19,000-12,000 B.P. These floods ravaged the Columbia Plateau, washing away loess and other sediments and eroding large channels into the basaltic bedrock. The landform complex thus formed is called the Channeled Scabland.

Type de document :
Article de périodique

Source :
Terra Helsinki, 1984, vol. 96, n°. 2, p. 95-106, Références bibliographiques : 20 réf.

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