Geology Reference
In-Depth Information
The Belknap lava field in the central Cascades
began with eruptions 1,600 years ago blocking the
McKenzie River to the northeast.
years ago. As the cinder crater developed, several
fluvial drainage channels were blocked by lava to create
Spring Lake and Linton Lake.
South of the Three Sisters, eruptions from a
number of vents in the region of Mt. Bachelor took
place about 2,000 to 18,000 years before the present.
Coinciding with a time of glacial retreat, a 15-mile long
series of cones extruded a total of 7 cubic miles of lava
that covered 83 square miles. These volcanic episodes
were not continuous but took place sporatically from
several fissures in the Mt. Bachelor chain. The oldest
flows from cracks alongside Sheridan Mountain were
followed shortly by those of Red Crater, Katsuk Butte,
and Siah Butte. Once the cones of the Siah group had
formed, volcanic activity shifted northward to Mt.
Bachelor and Kwolh Butte where the latest flows built
a small cone on the north side of the mountain.
Northern High Cascades
Mt. Hood
At the northern end of the Oregon Cascades,
Mt. Hood is the highest peak in the state at 11,235
feet. The mountain is named for Samuel Hood, a baron
with a successful career in the British Royal Navy who
was stationed in American waters during the American
Revolution. One of the younger members of the High
