About the Talk

Eruptive History and Hazards of the Mount Baker Volcanic Field

On a clear day in Port Townsend, you can’t help but notice Mount Baker to the northeast, just beyond Bellingham. Just 60 miles away, this spectacular volcano lies restless, its history largely unknown until recently.

 The geologic history of the Mount Baker Volcanic Field is now well documented for the past 3-4 million years. The ice-mantled cone of Mount Baker is but the youngest in a long series of eruptive centers, which includes two calderas (large eruptive cauldrons). The past 10,000 years (the Holocene) has seen a decrease in “constructional” lava flows.

Conversely, “destructional” events, such as flank collapses that evolve into far more hazardous lahars are now recognized as the Holocene norm at Mount Baker. Mount Bakers historical record begins in 1843 and ironically is among the most obscure, despite eye-witnesses reports and newspaper accounts. The reasons for the famous “failed-eruption” of 1975 is the latest example of the historic puzzle; this event provided the backdrop to the modern age of volcano monitoring in the Cascade and Aleutian arcs.

About the Speaker

Dave Tucker is a Research Associate in the Geology Department at Western Washington State University (Bellingham) and Director of the Mount Baker Volcanic Research Center, which is the nucleus for ongoing volcanic research at the mountain. Dave has published (2019) Geology Underfoot in Western Washington. The book features several dozen field trips to exciting geologic sites in our region.

Book – Geology Underfoot in Western Washington (field trip guide)

About the Talk

The great Missoula floods and other megafloods of the Columbia River:  Agents of catastrophic landscape change in Washington

Dr. Richard Waitt of the U.S. Geological Survey (Vancouver, WA) will present a fascinating review of the Great Missoula Floods, which has been a topic of interest of his for several decades.

As a result of more than 40 years of research, the great Missoula flood is now known to have consisted of perhaps 100 repeated floods that occurred intermittently across several millennia. A single monstrous ‘Spokane Flood’ was first proposed in J Harlan Bretz in 1923, as an agent of catastrophic landscape change in Washington. The hypothesis of scores of gigantic Missoula floods was proposed and developed by Richard Waitt and Brian Atwater in the late 1970s to late 1980s.

Between about 18,500 and 15,000 years ago, immense floods from glacial Lake Missoula in Idaho and Montana drowned the Wenatchee reach of the Columbia Valley by different routes. The earliest debacles raged 1,000 feet deep down the Columbia and built the high Pangborn bar at East Wenatchee.

After advancing ice blocked the Columbia valley north of Spokane, several great floods descended Moses Coulee (channel) and up the Columbia past Wenatchee. When ice covered intakes to Moses Coulee, the Grand Coulee and Quincy basin became the westernmost floodway. Receding ice-dammed glacial Lake Columbia until it burst. Smaller great flood(s) swept down the Columbia probably from glacial Lake Kootenay in British Columbia. Huge fluted points produced by early man (Clovis) atop Pangborn bar were buried by loess starting about 13,000 years ago. Although Clovis people came to the Northwest two millennia after the last Missoula flood they may have seen outburst flood(s) from glacial Lake Kootenay.