Geology Reference
In-Depth Information
the north, this feature was referred to as "the crack" by
homesteaders. Here picnics were held and ice cream
made using ica deep from within the crevasses of the
chasm.
clams and snails found in the strata below the lava of
During the Pleistocene successive flows of
Wrights Point are evidence of the stream environment.
pahoehoe lava here piled up 70 feet thick in places,
only to be covered later by streams of hummocky black
Smith Rock
aa lava. These basalts originated from Green Mountain
Smith Rock State Park, seven miles northeast
and the Four Craters volcanoes. With the Four Craters
of Redmond, is nationally renowned by rock climbers.
eruption, a small tectonic depression or graben ap-
The name for the park goes back to early Oregon
peared about 2 miles wide extending south into the
history. In 1863, soldiers, in pursuit of local Indians,
Christmas Lake basin. Crack-in-the-Ground opened in
were camped near Smith Rock when one of the men
the lavas when the central block began to drop down
named Smith climbed to the top of the monolith to get
to create the graben and trigger the crack seen on the
a better view. Unfortunately the boulder on which he
surface. In a wetter environment than eastern Oregon,
was standing rolled out from under his feet.
such geologic features would have been rapidly filled in
On the very northwestern edge of the Lava
with sediment and rubble or covered by vegetation.
Plains province at Smith Rock State Park successive
colorful tuffs in the canyon of the Crooked River have
Wrights Point
been eroded to create the fantastic rock shapes visible
Lava flows following a prehistoric stream bed
in the cliffs. In the park, the river winds its way past
have created a 150 foot high sinuous ridge named
massive, towering rock walls, picturesque pinnacles,
Wrights Point 12 miles south of Burns. Extending a
crags, and great slabs of upright rocks. Smith Rock,
distance of 6 miles, the flat-topped ridge averages 400
one of these vertical pillars, is part of a volcanic center
yards wide before it merges with a broad mesa at its
which erupted 18 to 10 million years ago. Included with
western end. Wrights Point is an excellent example of
Smith Rock are Gray Butte, Coyote Butte, Skull
inverted topography. During late Pliocene time, a
Hollow, and Sherwood Canyon, all of which are part of
succession of fluid lavas followed an ancient, winding
a larger Gray Butte complex of volcanoes. Rhyolitic
stream valley eventually filling in the canyon and
lavas, emerging from vents near the Crooked River,
hardening. As erosion took place, the softer rocks and
marked the beginning of the Gray Butte events. Falling
soils of the adjacent valley walls were eroded away,
ash expelled from the volcanoes covered the region to
leaving the streambed cast in lava projecting above the
be followed by mud flows and more volcanic debris
surrounding plain. Fossilized fish bones and freshwater
ejected during subsequent eruptions. The land surface
