We welcome back USGS geologist, Ralph Haugerud, to present new understanding of glacial topography from lidar imagery. He will focus on what happened when the ice melted. Join us (in person) at the First Baptist Church, Port Townsend, 4 pm. The event will also be filmed for viewing afterwards.
The Lecture: Post-mortem of the southern Cordilleran Ice Sheet
Death of an ice sheet can have many causes, as shown by retreat of the southern Cordilleran Ice Sheet about 15,000 years ago. East of the Cascades, the margin of active south-flowing ice retreated north as less snow fell and more melted. West of the Cascades, the Juan de Fuca lobe of the ice sheet appears to have floated away in response to rising sea level, perhaps without a proximal climatic cause. Collapse of the Juan de Fuca lobe diverted ice from the Puget lobe, which consequently stagnated at its margin and rapidly melted back. Later Sumas ice readvance in the Fraser Lowland may reflect stabilization of the remnant ice sheet by grounding as local sea level fell, followed by climate-driven retreat.
Ralph Haugerud, is a Seattle native, with BS and MS degrees from Western Washington University and a PhD from the University of Washington. He began his career looking deep in the Earth’s crust at gneiss and tonalite in the North Cascades, moved on to study turbidites, then glacial till, and now spends much of his time looking at lidar topography. He is employed by the USGS and lives in Wenatchee, Washington.
The Lecture: Soil-climate evidence for timing of the Cascade uplift and creation of its rain shadow
Calcrete is a CaCO3-rich hardpan paleosol that forms in dry, stable landscapes of the world. Calcrete in eastern Washington cements a 20-m-thick interval across three geomorphic domains: Palouse Hills, Channeled Scablands, and Yakima Fold Belt. The sheet-like calcrete deposit encloses ancient Scabland flood gravels and defines a regional paleosurface that has been bent and broken by Quaternary faults. Calcrete overprints primarily lowland alluvial deposits (ancestral Columbia-Snake River floodplain) and basaltic alluvial fan gravels shed from fault-bounded ridges. Thick layers of pedogenic carbonate accumulated during the Pleistocene, between about 1.8 million years ago to about 40 thousand years ago, but older cements at somewhat deeper levels date back to ~7 million years (late Miocene). The appearance of arid-land calcrete in eastern Washington coincides with the topographic rise of the Cascade Range and establishment of a strong rain shadow east of the divide. This lecture sheds new light on this lesser-known part of eastern Washington’s stratigraphy.
Skye is a field geologist who specializes in mapping, paleosols, and geomorphology. His work focuses on the interplay between tectonics, topography, and climate. Skye received his BSc. in Geology from Whitman College and his MSc. from the University of Wyoming. He has been a Soil Scientist for the Colville Confederated Tribes and taught Geosciences at Boise State University.
Currently, Skye is mapping the surficial geology of the Mission Valley in northwest Montana and sorting out the geomorphic history of calcretes in Eastern Washington. Skye’s hobbies include woodworking, nordic skiing, and motor-cycles. Skye is married to Hilary, manager of the Grizzly Bear Program for the U.S. Fish and Wildlife Service. They live with their hound dog, Lucy, in northwest Montana.
Nan Evans of KPTZ and Seattle Naturalist David Williams, discussed “A Sense of Place – What is it?” This is a prelude to David’s March 18th lecture entitled “Secrets of Seattle Geology—Connections of the human story and the geology story.”
The interview was delivered for Nature Now, a weekly radio broadcast on KPTZ 91.9 MHz. The interview was recorded as a MP3 file and broadcast three times preceding David’s March 18, 2023 lecture for the Quimper Geological Society:
Show #610: David Williams—A Sense of Place: What does that mean?
Broadcast on March 15 at 12:30 PM; March 16at 5:30 PM; and March 18 at 12:30 PM