This view of the mountain and its volcanic crater clearly shows the central dome, the toe of the surrounding glacier (world’s fastest moving!), and red hydrothermally altered rock on Mt. St. Helens.

Takeoff from helipad from North Fork Survivors tourist compound. This is bigfoot country!

On the way up the Toutle River, we cross a recently built sediment dam.

Flying up the river we see that the most recent lahar passes through and has eroded past lahars.

Up at Spirit Lake we can see how high the lake sloshed up on this protruding peninsula. The landslide which initiated the eruption in 1980 was soon overtaken by the lateral pyroclastic blast, which leveled the trees on the peninsula before the landslide hit the lake. The sloshing dislodged the flattened trees and those are the logs you see floating in the lake today. So, the areas on the peninsula not covered with logs are where the lake sloshed.

Looking up towards the mountain from Spirit Lake, one sees the landslide material which initiated the 1980 eruption.

Streams have made deep cuts in the Mt. St. Helens landslide.

Cross sections through the structure of the mountain can be glimpsed from the helicopter.

Cross sections reveal hydrothermal alteration in the rocks.

The glacier in the crater is sandwiched between the central cone, left, and the wall of the crater, right.

Recent lahar surface shows progress of growth and channel working that have been happening since the 1980 eruption.

The GSOC field trip group poses with pilot Robert. Left to right are Steve Haar, Cecily Cedilote, Sheila Alfsen, pilot Robert, kneeling, Charles Montross, Anne Oneill, kneeling, Carol Hasenberg, Yumei Wang. Bo Nonn also participated in the trip.

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2017 Mt St Helens Helicopter Tour

Geological Society of the Oregon Country (GSOC)

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