Vanished Volcano
Posted by: Groundspeak Premium Member Volcanoguy
N 42° 44.035 W 122° 01.034
10T E 580448 N 4731735
Geologic history sign titled Vanished Volcano, about formation of Crater Lake.
Waymark Code: WM7KEF
Location: Oregon, United States
Date Posted: 11/04/2009
Published By:Groundspeak Premium Member silverquill
Views: 6

Marker Name: Vanished Volcano
Marker Text: For thousands of centuries the landscape in front of you was dominated by a massive and explosive volcano called Mt. Mazama. Like today’s major Cascade stratovolcanoes, it slept for long intervals under a mantle of ice and snow, periodically bursting into activity.
About 7,700 years ago a series of dramatic eruptions shook Mt. Mazama. Rocks and ash exploded into the air and fell hundreds of miles away. Avalanches of glowing-hot rocks poured from the volcano, creating the flat valley you are standing on. Then, the top of Mt. Mazama collapsed, leaving behind a 6-mile wide (10 km) caldera.
Today the base of Mt. Mazama contains the deepest lake in the United States -- Crater Lake. You are now standing at about the same elevation as the lake bottom, more than 1,900 feet (580 m) below the water’s surface.
Just ahead 3 1/2 miles (5.6 km) lies the south entrance to Crater Lake National Park which preserves the magnificent legacy of Mt. Mazama for all to enjoy.

NEW and UPDATED Marker and Text:

From here you can see the truncated peaks of an enormous volcano that stood about 12,000 feet, towering over the landscape. Formed slowly over half a million years, the destruction of Mount Mazama took only days. Its climactic eruption 7,700 years ago began with a blast of rock and ash blown into the stratosphere. New vents encircling the peak brought hot flows of pumice, ash, and gas down its flanks burying the landscape, creating this flat valley. So much of the magma chamber was drained, the volcano had no support. It fell in a massive collapse, creating the basin that would hold Crater Lake. You are standing at about the same elevation as the bottom of Crater Lake.

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  
OregonTrailRanger visited Vanished Volcano 11/27/2020 OregonTrailRanger visited it
NW_history_buff visited Vanished Volcano 10/19/2013 NW_history_buff visited it
Volcanoguy visited Vanished Volcano 08/25/2009 Volcanoguy visited it

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