claim: 2.6 million years is how far Cordilleran Ice Sheet dates back to.
evidence: The Cordilleran ice sheet was a major ice sheet that periodically covered large parts of North America during glacial periods over the last ~ 2.6 million years .. ice sheet. ice sheet. North America. North America. This included the following areas  :. Western Montana. Western Montana. Western Montana. The Idaho Panhandle. Idaho Panhandle. Idaho Panhandle. Northern Washington state down to about Olympia and Spokane. Washington state. Washington ( state ). Olympia. Olympia, Washington. Spokane. Spokane, Washington. All of British Columbia. British Columbia. British Columbia. The southwestern third or so of Yukon Territory. Yukon Territory. Yukon. All of the Alaska Panhandle. Alaska Panhandle. Southeast Alaska. South Central Alaska. South Central Alaska. South Central Alaska. The Alaska Peninsula. Alaska Peninsula. Alaska Peninsula. Almost all of the continental shelf north of the Strait of Juan de Fuca. continental shelf. continental shelf. Strait of Juan de Fuca. Strait of Juan de Fuca. The ice sheet covered up to 2.5 million square kilometres at the Last Glacial Maximum and probably more than that in some previous periods , when it may have extended into the northeast extremity of Oregon and the Salmon River Mountains in Idaho .. ice sheet. ice sheet. Last Glacial Maximum. Last Glacial Maximum. Oregon. Oregon. It is probable , though , that its northern margin also migrated south due to the influence of starvation caused by very low levels of precipitation .. starvation. starvation ( glaciology ). At its eastern end the Cordilleran ice sheet merged with the Laurentide ice sheet at the Continental Divide , forming an area of ice that contained one and a half times as much water as the Antarctic ice sheet does today .. ice sheet. ice sheet. Laurentide ice sheet. Laurentide ice sheet. Continental Divide. Continental Divide of the Americas. Antarctic ice sheet. Antarctic ice sheet. At its western end it is believed nowadays that several small glacial refugia existed during the last glacial maximum below present sea level in the now-submerged Hecate Strait and on the Brooks Peninsula in northern Vancouver Island .. refugia. Last Glacial Maximum refugia. sea level. sea level. Hecate Strait. Hecate Strait. Brooks Peninsula. Brooks Peninsula. Vancouver Island. Vancouver Island. However , evidence of ice-free refugia above present sea level north of the Olympic Peninsula has been refuted by genetic and geological studies since the middle 1990s .. refugia. Last Glacial Maximum refugia. sea level. sea level. Olympic Peninsula. Olympic Peninsula. The ice sheet faded north of the Alaska Range because the climate was too dry to form glaciers .. ice sheet. ice sheet. Alaska Range. Alaska Range. glaciers. glaciers. Unlike the Laurentide ice sheet , which is believed to have taken as much as eleven thousand years to fully melt , it is believed the Cordilleran ice sheet , except for areas that remain glaciated today , melted very quickly , probably in four thousand years or less .. ice sheet. ice sheet. Laurentide ice sheet. Laurentide ice sheet. This rapid melting caused such floods as the overflow of Lake Missoula and shaped the topography of the extremely fertile Inland Empire of Eastern Washington .. floods. floods. Lake Missoula. Lake Missoula. Inland Empire. Inland Empire ( Pacific Northwest ). Eastern Washington. Eastern Washington