The Heat from Within: earthly insights into planetary volcanism

The Heat from Within Teacher Training Workshop


The lava flow we visited on the way to Santiam pass is part of the Belknap shield volcano, which lies on the axis of the Oregon high Cascade peaks between the North Sister and Three-Finger Jack volcanos. Our bus could not go to Belknap, but I was able to after the conference in a rental car. These views are taken from, and near, the Dee Wright volcano observatory atop McKenzie pass.

Belknap Shield

The Belknap shield volcano, viewed from the road at the top of McKenzie pass. Montage of three images; credit. To the left of the image is the long shallow slope of the shield, heading off the the basalt lava flow we visited along the road to Sanitam pass (Rich's flow). The steeper slopes that crown Belknap are of a cinder cone; another cinder cone is just below and right (east) of the crown (see next image). All the rock here is basalt.

What is the hill slope angle of the Belknap shield volcano, and how does it compare with other basalt shield volcanos?

Red Cone
not a'a

This red cinder cone, part way up the Belknap shield, has been partially engulfed by younger flows of basalt lava. Presumably, this cinder cone was the source of other basalt lava flows. They are now buried, among the many many individual lava flows that make up the shield volcano. Credit.
The lava flows here have slab-like tops -- neither a'a nor pahoehoe. The depression in the mid-distance is the remains of a lava tube, with the top collapsed in. The youngest flows here (like Rich's flow) are about 1400 years old. Credit.
is a'a
Stuck Truck

Looking north from the Dee Wright observatory, across a field of a'a lava (note asphalt path at left for scale). The eruption that made these flows ws 2600 - 2900 years ago. In the distance are two glaciated stratovolcanos: Mt. Washington (left) and Mt. Jefferson (right). Credit.

The road to Belknap volcano and the Dee Wright observatory (McKenzie pass) is definitely not for a bus. When I drove the road, this semi-truck was stuck on the a'a, with just enough room for my subcompact rental to pass by. After a few minutes, the truck managed to move forward, and find a place to turn around to go back to Bend. Credit.

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Copyright Allan Treiman, LPI.
Updated 07/28/06.
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