Geology Reference
In-Depth Information
large areas of clinkery chunks of broken aa lava and
Diamond Craters
black swirly pahoehoe lava. Oozing from fissures,
To the south and east of the lava fields near
several large spatter cones were built up by cooling
Bend, Diamond Craters in Harney County is one of the
lava. Flows from the shallow Squaw Ridge cone
most dramatic of Oregon's volcanic attractions, display-
covered over 200 square miles, while the adjacent
ing a varied landscape produced by late Miocene to
Devils Garden is 45 square miles of lava, rubble, ash,
Pleistocene eruptions. Named for the diamond-shaped
basaltic bombs, and lava tube caves. Numerous small
cattle brand of an early settler, the craters are easy to
caves were formed by molten lava streams. In one of
reach. Within a 22 square mile natural area south of
these, Derrick Cave, a collapsed roof forms the en-
Malheur Lake, over 100 cinder cones and craters can
trance. At spots along the tunnel of the cave, the roof
be seen, 30 of which are located inside a 3,500 foot
rises as high as 50 feet. Benches inside the lava tube
wide caldera which has collapsed to a depth of 200
give the cave a keyhole-shape in cross-section to show
feet.
that the lava drained out slowly enough to leave behind
About 9 million years ago vents here pumped
a lining along the wall.
out ash and lava to cover 7,000 square miles of south-
east Oregon in layers up to 130 feet thick. This initial
activity was followed by a series of explosions and
intrusions 2,500 years ago forming small cinder cones
accompanied by vast new lava flows. A surge of mag-
The Devils Garden offers 45 square miles of rough
black lava flows, spatter cones, and lava tubes in
northern Lake County.
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