
LEGACY - Lava Rock - Deschutes County, Oregon
Posted by:
Volcanoguy
N 43° 55.061 W 121° 21.353
10T E 631998 N 4864043
FORMER: Geology sign on crater rim trail.
Waymark Code: WM3Y0G
Location: Oregon, United States
Date Posted: 06/02/2008
Views: 17
Geology sign on crater rim trail.
Marker Name: Lava Rock
Marker Text: The rock fragments which make up this butte are called scoria and include cinders, volcanic bombs and finer ejected materials. These rock fragments were thrown from the crater as molten masses of lava. Enclosed gases, which had been under greater pressure deep under the ground, expanded and broke the masses into smaller fragments. When the molten material cooled into rock, the remaining gas bubbles are retained as vesicles (rounded holes).
In contrast, the lava flow at the base of the butte had degassed to a point where not enough gas was available to throw the lava into the air. Instead, the lava flowed out of the weakest side of the cone.
The scoria and lavas from Lava Butte are an igneous rock called basalt, high in iron, calcium, and magnesium bearing minerals.
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