Riley Ranch Field Trip
Led by Bob Jensen
Wednesday, April 26, 9:00 am - 1:00 pm
Please join Bob Jensen, retired Deschutes National Forest geologist, as we explore Riley Ranch park. This is a reprise of the inaugural COGS field trip with new research on boulder deposits and their implication for massive paleo floods.
Over the last half million years the Deschutes River and it’s tributaries have been forced to cut new channels multiple times due to eruptions originating from the Cascades to the west and Newberry Volcano to the south. In the Bend area the last major change in the river’s location occurred about 65,000 years ago with the eruption of the basalt of Bend, which underlies much of Bend east of the Deschutes. The vent for this eruption (now buried by younger flows) was located on the north flank of Newberry in the Mokst Butte area and the flows extend west to block the river and northward to the south edge of Redmond. Following this eruption the Deschutes River began cutting a new channel along the western edge of the basalt of Bend and at some time a massive flood passed through Bend with the most obvious deposits from this flood occurring at Riley Ranch Nature Reserve. The wide variety of volcanic and erosional features within the Riley Ranch Nature Reserve makes it the most geologically interesting park in the Bend Park & Recreation District system and the trail system allows a convenient look at five million years of Central Oregon’s geologic past.
Contact the field trip coordinator, Derek Loeb ( DerekLoeb@gmail.com ), with questions.
Please note that this event is limited to 15 participants and registration must be done via the registration button on the trip listing on the COGS website. Successful registration will be confirmed on the webpage by a light green box indicating registration was successful and by a confirmation email. If you don't get this email you should try the registration process again. If the trip is full, please join the wait list.
Central Oregon Geoscience Society
P.O. Box 2154, Bend, Oregon 97709