Geologist Jim Baichtal will discuss revising old theories regarding how life adapted to Southeast Alaska’s ancient ice sheets during today’s Fireside Lecture at the Mendenhall Glacier Visitor Center.
Once thought to be completely covered by glacial ice to the shoreline, Southeast Alaska is now believed to have had significant ice-freerefuge areas where people, plants and animals lived.
“Exploration of caves yielded bones of mammals, birds and fish dating beyond the limits of radiocarbon dating methods,” said Baichtal. “Discoveries revealed that animals have been on the landscape for well over 50,000 years, refuting previous models of glaciation.”
The new model for glaciation involves the dynamic processes of glacial ice on the land and sea levels. As the glaciers grew, global sealevels fell, Baichtal writes. The weight of the advancing glaciers depressed the earth’s surface while pushing up a forebulge along theirfront. As the glaciers melted, sea level rose and the lands depressed by the weight of the ice rapidly rebounded and the forebulgecollapsed. Subsequent tectonic uplift has further changed the landscape.
Deposits of ocean shells found high on mountain slopes helped to define just where past shorelines were and the timing of deglaciation.These deposits also helped to predict early human habitation sites, which archaeological investigations have confirmed.
“This information is absolutely fascinating,” said Tongass National Forest naturalist Laurie Craig. “I am thrilled Jim will be presenting it to our Fireside audience.”
Fireside Lectures are free and occur at 6:30 p.m. and repeat at 8 p.m. Doors open at 6 p.m. Elevators are closed for replacement. Access to the visitor center is via an outdoor ramp or stairs. For more information, contact Laurie Craig at 789-0097 or lcraig@fs.fed.us.
