at its maximum extent continental glacial ice in north america extended as far south as siberia.
at its maximum extent continental glacial ice in north america extended as far south as siberia.
at its maximum extent continental glacial ice in north america extended as far south as?
siberia
in north america, the ice covered essentially all of canada and extended roughly to the missouri and ohio rivers, and eastward to manhattan. in addition to the large cordilleran ice sheet in canada and montana, alpine glaciers advanced and (in some locations) ice caps covered much of the rocky mountains further south. latitudinal gradients were so sharp that permafrost did not reach far south of the ice sheets except at high elevations. glaciers forced the early human populations who had originally migrated from northeast siberia into refugia, reshaping their genetic variation by mutation and drift. this phenomenon established the older haplogroups found among native americans, and later migrations are responsible for northern north american haplogroups.
last glacial maximum
the last maximum extent of glaciation, known as the last glacial maximum, was approximately 18,000 years ago. this last returning advancement of glacial ice approaching the ohio valley began 30,000 years ago. west virginia had no ice sheet buildup during this time. during the last ice age smaller glaciation impounded lakes continued to collect precipitation on the plateau. these chilly lakes among mountain peaks were separated from the continental ice sheet to the north. the deeply carved river valleys, such as the upper canaan valley to blackwater canyon and the dolly sods wilderness to cheat river areas, are called paleozoic plateaus. the "driftless area" drains into rivers having rugged regions of bluffs and valleys. according to the west virginia geological and economic survey, the two large ice age lakes varied throughout the epoch. the last glacial lake, monongahela, has been dated by carbon-14 testing to between 22,000 and 39,000 years old. it reached as far south as weston, west virginia. the first ice-damming event was a pre-illinoian (stage) lake, which outburst during the earlier ice retreat towards the northwest pittsburgh drainage basin. the last occurrence of the monongahela lake outburst was an outwash gravel dam backed up slackwater at allegheny-monongahela confluence during an illinoian ponding event during the last glacial retreat. the last outburst drained the water to its present course in the central allegheny mountains or northern tributaries of the state feeding the monongahela and ohio rivers.
prehistory of west virginia