The Ancestral Deschutes River - Deschutes County, Oregon - Oregon Historical Markers on Waymarking.com

This sign is located along the Deschutes River Trail about a tenth of a mile south of the Meadow Trailhead.

Marker Name: The Ancestral Deschutes River
Marker Text: During the past half million years, the Deschutes River has been caught between the violence of two volcanic forces. Repeated eruptions in the Cascades pushed the river eastward while eruptions from Newberry Volcano pushed it westward. In more recent geologic times, successive lava flows forced the river to relocate farther and farther to the west.
The most recent relocation of the river and formation of Lava Island occurred 6200 years ago when Lava Butte erupted. The two river channels flowing on either side of Lava Island begin approximately a mile upstream.

This sign is 15 to 20 years old and uses 6200 years as the age of the Lava Butte flow but these are 6200 C14 years before 1950 AD. The concentration of carbon-14 in the atmosphere has varied over time and as a result C14 years are not the same as calendar years. More recent work has allowed the development of calibration curves, so today the generally excepted age for the Lava Butte eruption is 7000 years before 1950 AD. This eruption filled about four miles of the previous river canyon with lava.

An earlier eruption about 78,000 years ago filled over ten miles of river channels and diverted the river into a new channel that was more than 50 miles long before the river reentered its old channel. For more on the ancestral Deschutes River check page 58 on the web link below.

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