Lake Condon was a temporary lake in the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

region of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, 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 las ...

from 15,000 to 13,000 BC. The restricted flow of waters from cataclysmic floods from

Glacial 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 Mic ...

, and pluvial

Lake Bonneville Lake Bonneville was the largest Late Pleistocene paleolake in the Great Basin of western North America. It was a pluvial lake that formed in response to an increase in precipitation and a decrease in evaporation as a result of cooler temperature ...

through the constriction of the

Wallula Gap Wallula Gap () is a large water gap of the Columbia River in the northwest United States in southeast Washington. It cuts through the Horse Heaven Hills basalt anticlines in the Columbia River Basin, just south of the confluence of the Wall ...

in the

Horse Heaven Hills The Horse Heaven Hills are a long range of high, rolling hills in Klickitat, Yakima, and Benton counties in Washington. The hills are an anticline ridge in the Yakima Fold Belt formed by north–south compression of lava flows in the Columbi ...

flowed into south-central

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

and north-central

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 ...

, and were backed up by 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 st ...

, forming Lake Condon. The water remained for a period of 5–7 days before the flood waters drained through the Columbia River Gorge. Lake Condon reached an elevation of about 1200 feet above sea level (today's sea level) before subsiding. Lake Condon also flooded the Umatilla and John Day river valleys.

Glacial Lake Missoula

During the last Ice Age (18,000 to 12,000 years ago), and in multiple previous Ice Ages, cataclysmic floods inundated portions of the Pacific Northwest from

pluvial In geology and climatology, a pluvial is either a modern climate characterized by relatively high precipitation or an interval of time of variable length, decades to thousands of years, during which a climate is characterized by relatively high ...

, and perhaps from subglacial outbursts. Glacial Lake Missoula was a body of water as large as some of the USA's

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

. This lake formed from glacial meltwater that was dammed by a lobe of the Canadian ice sheet. Episodically, perhaps every 40 to 140 years, the waters of this huge lake forced its way past the ice dam, inundating parts of the Pacific Northwest. Eventually, the ice receded northward far enough that the dam did not reform, and the flooding episodes ceased.

Evidence for Lake Condon

Columbia River Gorge

Although the river slowly eroded the land over this period of time, the most drastic changes took place at the end of the last ice age when the

cut the steep, dramatic walls that exist today. The gorge provided a hydraulic dam which backed waters up for days before it drained.The Seattle Times' ''Pacific NW'' magazine
- "Trailing an Apocalypse" - 30 September 2007 This quick erosion left many layers of

volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic ...

exposed.

Touchet-like formation

Lake Condon backflooded into the Umatilla and John Day River Valleys. In these relatively calm arms of the lake, the slackwaters were thick with suspended materials eroded from the scablands above. Some of the suspended materials settled out, creating thick sediment layers which are found throughout these valleys. These sediment layers are part of the

Touchet Formation The Touchet Formation or Touchet beds consist of large quantities of gravel and fine sediment which overlay almost a thousand meters (several thousand feet) of volcanic basalt of the Columbia River Basalt Group in south-central Washington (U.S. ...

Glacial erratics

The maximum elevation of the flood, as established by other indications, is confirmed by

glacial erratics A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...

, which were stranded on the slopes up the John Day and Umatilla river valleys and other elevated regions in the mid-Columbia at elevations of up to 1200 feet (366m) above sea level.

References

External links

* * {{Washington erratics Condon, Lake