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July 1998 Field Trip Review

• Date: July 11, 1998
• Guest Speaker: Ken Cameron, DEQ, formerly USGS
• Topic: "The Buried Forests of Mt. Hood"
• Location: Old Maids Flat and Clear Fork of the Sandy River, near Zigzag, Oregon, and the upper White River Canyon near Timberline Lodge
• Reference Article: Cameron, Kenneth A., and Pringle, Patrick T., Prehistoric Buried Forests of Mount Hood, Oregon Geology, March 1991

The purpose of the field trip was to observe ancient forests which had been buried by pyroclastic flows from Mt. Hood in the 1700's. In the two locations located in the forests at the base of Mt. Hood we saw numerous ancient Douglas fir and cedar snags poking through the forest floor or through the stream beds. Tree wells, where the hot flows had incinerated the tree surrounded by the ash, were also prevalent. We also observed locations where the flows had backed up into tributaries of the Sandy River, now marked by a lake or marsh.

On the slopes of Mt. Hood we observed volcanic and glacial features on our way to observe a stand of trees affected by the ancient volcanic activity.

Here are some pics from the trip:

The GSOC crowd gets the briefing from Ken at Old Maids Flat

One of many snags we saw in Lost Creek.

More snags.

This is the ash layer deposited by the pyroclastic flow.

Evelyn Pratt and Carol Cole (now deceased) listen attentively while Ken describes how you can date rocks by measuring the size of certain lichen patches.

One of the larger snags coming up out of the ash layer in the forest.

A tree well in the forest.

On Mount Hood, we saw this magnificent volcanic bomb with the typical radial cracking pattern.

Ken explains about the interaction between glaciation and volcanic activity on Mount Hood.

Glacial striations in a boulder on Mount Hood.

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