How much we know about the Pacific Northwest’s post-Ice Age geologic events has grown rapidly in recent decades. The discovery and study of buried and submerged forests-Victims of past catastrophes, has opened the door to new understanding. Testing techniques such as Carbon 14 wiggle matching and dendrochronology (tree-ring dating) now allow more precise dating of the geological past as well. These capabilities are revolutionizing our understanding of the history, behavior, and effects of past volcanic eruptions, regional earthquakes, major landslides, and (to a limited extent) regional climate history and fluctuations.
We will take a snapshot tour of some of the many locations of buried and submerged forests around Washington State and other Pacific Northwest locations to observe trees that were submerged by postglacial tectonic forces, or killed by a flow of hot volcanic fragments (pyroclastic surge) or buried in landslides, or drowned in lakes dammed by landslides. On our tour we’ll get a picture of the scale of some of the dramatic postglacial landscape changes, such as the episodic disturbances caused by volcanism- changes that the pre-Euro-American settlement peoples experienced and adapted to, and that early explorers, like Lewis and Clark, described vividly in their journals.
We’ll see how samples of “subfossil” trees are collected and prepared for tree ring analysis, and learn about what tree rings in these “time capsules” can tell us. Some of the scenic areas we will visit include the Washington Coast, the Olympic and Cascade Mountains, the Puget Lowland, and the Columbia Gorge, with a special focus on the Bonneville landslide, and Mount Rainier and Mount Hood volcanoes (rescheduled from Oct. 26, 2019).
Pat Pringle is Professor Emeritus of Earth Sciences at Centralia College, Washington. He taught at Centralia College from 2005-2017 and was a Research Geologist at DNR Geological Survey of Washington from 1990-2005 and at US Geological Survey Cascades Volcano Observatory from 1982-1990. Pat studies volcanoes, earthquakes, landslides, and debris flows using radiocarbon and tree-ring analysis to establish the history of past geologic events. He is the author of books on the roadside geology of Mounts St. Helens and Rainier as well as many published papers and reports; the Mount Rainier book won the Geoscience Information Society’s “Best Guidebook Award” for 2009, presented at the Geological Society of America’s Annual Meeting that year.