Geologic Evolution of the Skagit River Watershed

Geologic Evolution of the Skagit River Watershed

Geologic Evolution of the Skagit River Watershed

Event Details

Jun 08, 2024 from 09:00 AM to 05:00 PM
Skagit River / North Cascades Highway
Activity Level
Class Tuition
Minimum Age
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Led by a retired North Cascades National Park geologist, this new Field Excursion explores how the Skagit River Watershed developed over the past several million years. An epic series of events—including glaciation, landslides, and volcanic eruptions—have shaped the nature of the region we know and love today. The Skagit’s watershed today is about three times as large as it was before the ice ages and a series of volcanic eruptions in recent geologic time.

After a brief slideshow orientation, our group will travel together to the famous Diablo Lake overlook, where we will learn how continental ice sheets rearranged the Skagit River drainage network, reversing the flow of the upper Skagit from the Fraser River south to the Skagit.


Formation of Skagit Gorge led to the capture of the upper Skagit Valley that reversed drainage from the Fraser River to the Salish Sea.

Our second stop will be at Damnation Creek, where an 8,000 year-old landslide blocked the Skagit River and created a lake that persisted for several centuries. The third stop near the town of Concrete will focus on evidence that an alpine valley glacier blocked the Skagit River from 29,000 to about 21,000 years ago, creating a glacial lake that likely drained to the south via the Sauk River Valley.

Our final stop near Lyman will look at deposits from Glacier Peak lahars that were deep enough at Darrington to divert the Sauk River into the Skagit about 6,000 years ago.

Rivers are dynamic forces of nature and there’s no better guide to help us better understand the evolution of the Skagit watershed then Jon Reidel!

Scholarships and Student, Military and Disability discounts are available for most in-person programs. Call (360) 854-2599 for more info.

Photos by John Scurlock