Prelude to the Big One - Crater Lake, OR
Posted by: Groundspeak Premium Member saopaulo1
N 42° 54.697 W 122° 08.576
10T E 569958 N 4751355
One of a few signs at Sinnott Memorial Overlook in Crater Lake National Park. Many of the plaque here deal with the lake's geological history.
Waymark Code: WMYXBE
Location: Oregon, United States
Date Posted: 08/05/2018
Published By:Groundspeak Premium Member Volcanoguy
Views: 2

The massive cliff of Llao Rock was formed by one of the last and biggest eruptions of lava prior to the main volcanic event. In fact, there is evidence that the explosion that formed Llao Rock may have triggered the major eruption of Mount Mazama about 170 years later. With the collapse of the volcano, we can see this lava flow atop an older crater basin.

Layers of History.. The deposit of Llao Rock caps a long volcanic history. It was formed when an active vent filled a crater with lava and cooled prior to the final climactic event that collapsed Mount Mazama, This flow is nearly 1200 feet thick and a mile long. Layers of ash, pumice, and lava beneath Llao Rock represents earlier stages of Mount Mazama's growth.
Historic Topic: Geological

Group Responsible for placement: National Parks Service

Marker Type: Trail

Region: Southern Oregon

County: Klamath

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

Web link to additional information: Not listed

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OregonTrailRanger visited Prelude to the Big One - Crater Lake, OR 11/27/2020 OregonTrailRanger visited it