The Pinnacles
Posted by: Groundspeak Premium Member Volcanoguy
N 42° 51.008 W 122° 00.434
10T E 581115 N 4744650
Geologic history sign at The Pinnacles Overlook.
Waymark Code: WM7MZN
Location: Oregon, United States
Date Posted: 11/10/2009
Published By:Groundspeak Regular Member silverquill
Views: 7

Marker Name: The Pinnacles
Marker Text: The history of the “pinnacles” below began about 7,700 years ago when the eruptions of Mt. Mazama were reaching their climax. Torrents of red-hot, gas-charged pumice poured down Mazama’s slopes at speeds of up to 100 mph (160 kph). On top of this came a flow of heavier rocks called scoria. These glowing avalanches flooded downslope for many miles, leaving deep deposits in their wake.
Temperatures in the deposits may have exceeded 750° F (400° C). Plumes of vapors appeared, as gasses escaped from the settling rocks through vents called fumaroles. Minerals in the gasses, combined with extreme heat, welded the sides of the fumaroles in the shape of slender cones. Since then, streams have eroded a canyon through the deposits, exposing the cones. Many of these fossil fumaroles are hollow.

Historic Topic: Geological

Group Responsible for placement: National Parks Service

Marker Type: Roadside

Region: Willamette Valley

County: Klamath

State of Oregon Historical Marker "Beaver Board": Not listed

Web link to additional information: Not listed

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Recent Visits/Logs:
Date Logged Log User Rating  
bachmann_andreas visited The Pinnacles 12/12/2011 bachmann_andreas visited it
Volcanoguy visited The Pinnacles 08/26/2009 Volcanoguy visited it

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