Tracing Volcanic Eruptions - Deschutes County, Oregon
Posted by: 
Volcanoguy
N 43° 59.585 W 121° 23.614
10T E 628809 N 4872358
A geologic history sign about volcanic eruptions along the Deschutes River Trail between the Meadow and Lava Island day use areas.
Waymark Code: WMGFF1
Location: Oregon, United States
Date Posted: 02/26/2013
Views: 3
This sign is located along the Deschutes River Trail about a half mile north of the Lava Island Takeout at a prominent exposure of the Tumalo Tuff.
Marker Name: Tracing Volcanic Eruptions
Marker Text: About 350,000 years ago, an area east of Broken Top erupted violently. Within a few hours, Bend and nearby areas were buried under 30 feet of windblown pumice. Ten, the same eruption sent red hot avalanches of ash and pumice down low areas and valleys at hurricane speeds. This added another layer 20 to 40 feet thick. Over time, the river exposed the avalanche deposits creating the overhangs and steep rock outcrops you see here.
There are problems with the cross section on this sign. The west side of the cross section is reasonable but the east side is totally wrong. The section shows older units beneath the west side unit passing beneath the river and making up the east side. Actually the east side contains the same units as the west side plus there are younger flows from Newberry Volcano at the top of the section and higher than the west side.
Historic Topic: Geological
Group Responsible for placement: Forest Service
Marker Type: Trail
Region: Central Oregon
County: Deschutes
State of Oregon Historical Marker "Beaver Board": Not listed
Web link to additional information: Not listed
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