Fort Rock, Volcanic Tuff Ring
Posted by: 
TheBeanTeam
N 43° 22.399 W 121° 03.960
10T E 656681 N 4804089
Fort Rock is a volcanic tuff ring that towers above the desert floor at what was once the shore of an ancient lake bed.
Waymark Code: WM1FY6
Location: Oregon, United States
Date Posted: 04/30/2007
Views: 162
Towering above the desert floor from a distance Fort Rock is impressive. Standing at the base of its tuff ring cliffs Fort Rock suddenly becomes awe inspiring.
A tuff ring is a "wide, low-rimmed, well-bedded accumulation of hyalo-clastic debris built around a volcanic vent located in a lake, coastal zone, marsh, or area of abundant ground water". 
Source: Volcanic and Geologic Terms.
Ground water coming in contact with molten lava resulted in a violent explosion that produced the circular "marr" that makes up this geologic wonder.
A lake once lapped at the edge of this marr and eroded the south wall of the tuff ring away. As you hike the inner circle of Fort rock you will walk across the sands of the beach approximately 20 to 30 feet above the floor of the old lake bed on what was once and island. The cliffs tower around 200 feet above the floor of the Fort Rock Basin.Source: Fort Rock Basin @ Volcano World.
Volcano World.