05-13-2017 Ned Brown: San Juan Islands

About the Talk

Geology of the San Juan Islands

The San Juan Islands record geologic growth of the western edge of North America by very active plate tectonics, which added exotic terranes ~400 to 100 million years ago. These terranes came from distant origins—Asia, Greenland, and the ancestral Pacific Ocean. The terranes moved through the ocean realm; they accreted by subduction at the continental edge, perhaps in N. California, at depths of 20-30 kilometers or more. These old rocks were then exhumed and transported north in a “forearc sliver” along the continental margin. They eventually collided with and stacked up on the south-facing edge of Wrangellia (Vancouver Island) and on the south end of the active Coast Plutonic Complex (a magmatic arc). At this point in San Juan Islands evolution, ~ 100 million years ago, the major tectonic elements were pretty much as they are now: The Islands were composed of stacked thrust sheets on the southeast edge of Wrangellia, and major plutonism emplacing younger rocks in the southern B.C. Coast Mountains.

An additional element to this tectonic wreck was the 100-65 million-year-old marine Nanaimo basin, surrounded by Wrangellia to the west, the San Juan Islands lying south, and the Coast Plutonic Complex on the east. A several kilometer-thick section of marine sands, conglomerates, and shales accumulated. These beds are rich in fossils, including a Tyrannosaurus dinosaur bone from Sucia Island. Distinctive cobbles give evidence of when the San Juan Islands terranes arrived. Sucia Island’s distinct horseshoe shape is a result of later folding into a syncline.

Unconformable on the Nanaimo Formation are the subaerial river-deposited sandstones, shales, and conglomerates of the Chuckanut Formation, ~60-50 million years old. These sediments accumulated to a thickness of some six kilometers (!) in a subsiding basin marginal to the coast. Fossil palm trees and crocodile footprints point to a tropical setting. Interestingly, the Chuckanut Sandstone is the major building stone for Port Townsend’s old masonry buildings.

Finally, during a period ~ 20,000 to 15,000 years, ago the San Juan Islands were overrun by a mile-thick glacier flowing south as an extension of the continental “Cordilleran Ice Sheet” lying mostly in Canada.

About the Speaker

Born and raised in Excelsior, Minnesota, Ned Brown attended Dartmouth College (A.B., 1960), the University of Otago, New Zealand (M.Sc., 1961-62 supported by a Fulbright scholarship), and the University of California, Berkeley (Ph.D., 1963-66) with his field area in New Zealand.

He was employed as a Geology Professor at Western Washington University from1966-1999, then was appointed as an Emeritus Professor. Over these years he supervised ~30 M.S. student theses, nearly all in the local region.

His geology research interests include metamorphism, structure, plutonism, plate tectonics while working extensively in the San Juan Islands, North Cascades, and Coast Mountains of southern B.C.

2017-06-10 Kitty Reed: Fort Worden geology field trip

About the Field Trip

Geology of Fort Worden—A 3-mile Hike and Beach Walk

When: Saturday, June 10th. 10:30 am – 3 pm (coincides with -1.5 ft low tide)

Where: Park your auto/bike/horse at the Fort Worden USO Building Lot, just west of the Taps at the Guardhouse Pub (old Information Center).

What: Geology of Fort Worden, plus some history of the old fort and the State Park. We’ll concentrate on the glacial sediments on the north-facing bluff but will also discuss marine landforms, erosion, drift cells, possible faulting, and tsunamis. After the walk (about 3 miles), there is an option to have beverages at the Taps at the Guardhouse Pub. Bring a pack, lunch, boots, and water (camera, binoculars); dress appropriately for the weather.

Who: Kitty Reed, Hugh Shipman, Carol Tepper, Michael Machette, Kevin Alexander & Leslie Aickin

How: Will accept registration postmarked after May 22nd. You must send your registration form and a check made out to Jefferson Land Trust for $10 per person to Leslie Aickin. No more than 2 persons per registration. No dogs or children under 16 yrs old. We’ll accept the first 25 persons to register and have a short standby list (hence the need for contact information).

  • To download a more recent guide for this trip click here*. The long version of the self guided field trip is found on the QGS website; titled:  2021-Fall:  Geology of bluff along North Beach, Fort Worden (updated 2023) – click here.     *This link is temporarily not working, check back soon 3/2024.

10-21-2017 Rob Wesson: Darwin & Geology

About the Talk

Darwin’s First Theory

Rob Wesson, an internationally known seismologist and now popular author, will speak about his new book, Darwin’s First Theory.  Everybody knows―or thinks they know―Charles Darwin, the father of evolution and the man who altered the way we view our place in the world. However, what most people do not know is that Darwin was on board the HMS Beagle as a Geologist―on a mission to examine the land, not flora and fauna. Or about Darwin’s seminal role in demonstrating and exploring the ups and down of the Earth’s crust.

Retracing Darwin’s footsteps in South America and beyond, Rob trekked across the Andes, cruised waters charted by the Beagle, hunted for fossils in Uruguay and Argentina, and explored sites of long-vanished glaciers in Scotland and Wales. As he followed Darwin’s path―literally and intellectually―he experienced the land as Darwin did, engaged with his observations, and tackled the same questions Darwin had about our ever-changing Earth.

Upon his return from his five-year journey aboard the Beagle, after examining the effects of earthquakes, tsunamis, volcanic eruptions, and more, Darwin conceived his theory of subsidence and uplift‚―his first theory. These concepts and attitudes―the vastness of time; the enormous cumulative impact of almost imperceptibly slow change; change as a constant feature of the environment―underlie Darwin’s subsequent discoveries in evolution. And this peculiar way of thinking remains vitally important today as we enter the human-dominated Anthropocene age.

As the New York Time Book Review wrote, Rob’s book “dares, thank goodness, to work some of the rare Darwinian territory that is actually underexplored. Tracing the young Darwin’s tracks …Wesson relates how Darwin hatched his first, favorite, and most overlooked substantive theory, on the origins of coral reefs. In both method and vision—imagining forms changing slowly over time in response to changing conditions—this precocious, even audacious idea anticipated and possibly inspired the theory of evolution Darwin would publish two decades later.”

About the Speaker

As a kid growing up in the Pacific Northwest, Rob Wesson became fascinated by mountains and glaciers. This interest led to a BS in earth science from MIT, and an M.Sc. and Ph.D. in geophysics from Stanford University. His career in earthquake research with the U.S. Geological Survey (USGS) spans four decades, where he is currently a Scientist Emeritus. In retirement, his research has turned to Chile where he is collaborating with a team exploring large earthquakes, tsunamis, and associated tectonic questions. This work has been supported in part by grants from the National Science Foundation. When not traveling to South America or elsewhere, Rob divides his time between his home in Evergreen, Colorado, and the rustic cabin he built near McCarthy, Alaska.

Rob first became interested in Darwin and his geology through reading The Voyage of the Beagle on a vacation trip to Patagonia. He became captivated by Darwin’s prodigious powers of observation and his insatiable need to understand and explain. Whatever rock, fossil, landscape, rodent, bird, or beetle that he found, he wanted to tell its story.