Geology of Shevlin Park
Thursday, April 18, 2019, 9 am-1 pm.
Saturday, April 27, 2019, 9 am-1pm.
Trip Leader: Bob Jensen
Within Shevlin Park are exposures which reveal more than 600,000 years of Central Oregon geologic history. Three ash-flows have come out of the Cascades west of Bend. Between eruptions, streams have cut channels into earlier ash-flows and those channels helped guide the flow of later ash-flows and lava flows. The current route of Tumalo Creek began forming around 300,000 years ago when a lava flow filled the previous channel east of Shevlin Park. About 170,000 years ago, another ash-flow swept across the area. A portion was channeled down the Tumalo Creek drainage where it thickened and welded to form what is now known as the Shevlin Park Tuff. Continued erosion by Tumalo Creek has cut a channel through the Shevlin Park Tuff to exposes the older Tumalo Tuff and Desert Spring Tuff. Total walking distance will be about 2.5 miles with about 200’ of elevation gain on a combination of trail, road and a minor amount of off trail surfaces. This trip should be suitable for all geological backgrounds. Each trip is limited to 12 participants.