Musings on Alaska during the last ice age


John Merck
April 26, 2011

The Pleistocene Epoch starting ~ two million years ago and ending 10,000 years ago, was punctuated by roughly thirty alternating glacial and interglacial intervals. Glacials were ice-ages that saw the formation of large continental ice sheets. Interglacials were warmer periods with conditions like today's. The last glacial maximum occurred 18,000 years ago. At that time:

Ecology of Beringia

Continental ice sheets require both cold summers and significant precipitation. Although cold enough to support continental ice, Beringia was too dry for them to form. Beringia was bordered by:

Thus, the fauna of Beringia looked more like that of eastern Siberia than that of North American "lower 48," south of the ice, but it was still distinct.

Within these boundaries was the mammoth-steppe a unique plant community, distinct from that of North America south of the ice and with no modern analog. Whereas modern central Alaska is dominated by moss and herb covered tundra or stunted taiga forest, the mammoth-steppe covering Beringia was dense grassland, vaguely similar to the prairies of great plains but colder and dotted with the shrub-like dwarf trees (e. willows) that we see today. We see evidence for it in the fossil record of land animals, pollen, and insects.

The mammoth-steppe environment owed its existence to a complex interaction of climate, physical geography, and plant and animal behavior.

Key facts:

Beringian bestiary

The major grazers:

Their major predators:

A final note:

Beringia was a staging-ground for the invasion of North America by several species at the end of the Pleistocene, around 11,000 years ago, when the Laurentide and Cordilleran ice separated, creating a corridor through Yukon and Alberta into Montana. Immigrants included: