On Tuesday, April 28th from 5:15-7 p.m., the Port Townsend Marine Science Center (PTMSC) welcomes research geologist Ralph Haugerud from the U.S. Geological Survey as a guest speaker to present “Investigating the wreckage of the last glaciation in Northwest Washington.” The presentation is part of the regular meeting of the Geology Study Group held at the Natural History Exhibit in Fort Worden State Park and is free to the public.
“We appreciate Mr. Haugerud taking time from his busy schedule to share his insights with our study group,” said Anne Murphy, executive director for the PTMSC.
The presentation will address new high-resolution lidar topography which discloses landforms that detail the waning of the last ice sheet. About 17,000 years ago, the ice sheet, flowing south from Canada, reached its maximum extent with a terminus a few miles south of Olympia. The distribution of relict meltwater channels details progressive northwards retreat of the ice margin.
Rather than a textbook retreat, with backing up of a still-moving glacier that delivered ice and rock debris to progressively younger and more northerly glacier margins, evidence suggests that ice in the Puget Lowland stopped moving and melted in place. This is possibly because the ice sheet in the Strait of Juan de Fuca collapsed and isolated Puget Lowland ice from its sources.
Haugerud is stationed in Seattle at the University of Washington where he studies the geology of the Pacific Northwest, concentrating on the North Cascades and, more recently, the Puget and Fraser lowlands with a special emphasis on earthquake hazards. He is co-author, with Rowland Tabor, of Geology of the North Cascades, published by The Mountaineers.