Glacial Geomorphology of the Santiam Pass Area Field Trip
August 5, 2018, 9 am – 3 pm, Led by Derek Loeb
The Quaternary Period ranges in age from about 2.6 million years ago to the present. Within this time period, numerous cycles of major glacial advances and retreats occurred. This is also a period when active volcanism in the High Cascades interacted with alpine glacial activity. During the last glacial stage from about 115,000-12,000 years ago, volcanic and glacial interactions resulted in much of the modern land forms of the High Cascades that are so familiar and appreciated today. The theme of this field trip will be to examine these land forms and to discuss the volcanic and glacial processes that produced them.
We will meet at 9 am at the Ray Benson Sno-Park, near Santiam Pass off of U.S. Hwy 20. After introductions and orientation we will discuss how glaciers have interacted with the High Cascade volcanos. With Hayrick Butte in clear view, this area is one of the best places in the world to examine a specific type of interaction of volcanism and glacial ice which results in a landform called a tuya.
We will then proceed east on Hwy 20 to the Mt. Washington Overlook pull off. Here we will enjoy a great view of Mt. Washington, but most importantly we will be able to envisage what the glacial accumulation zone and alpine glaciers would have looked like during the last glacial advance. We will also get a good view of Blue Lake, which is a post glacial, hydrovolcanic feature which sits within the larger Suttle Lake basin. Suttle Lake is a moraine-dammed lake that is just out of sight from this location.
Our final stop will be further east on Hwy. 20, past the northern shore of Suttle Lake, to FS 12/Jack Lake Rd. where we will park near the bridge over Lake Creek. Here we will use a little imagination to see the terminal moraine of Suttle Lake. We will hike about a mile, ascending its lateral moraine, before arriving at the recessional moraine that dams Suttle Lake. Here we will enjoy a lunch break with shade and a view of the lake. After a summary of what we have observed and interpreted, we will discuss features that are further downstream, for example the braided streams and outwash plains. We should arrive back at our vehicles by 3 pm.
Total walking distance on this trail is about 2 miles and an elevation gain/loss of about 200 feet which will be mostly in the shade. It should be suitable for all geologic backgrounds. Please send an email to DerekLoeb@gmail.com to register or for more information and include a cell phone number. Participants need to be a member of COGS or guest of a member and please leave your pets at home.
Central Oregon Geoscience Society
P.O. Box 2154, Bend, Oregon 97709