Ten miles west of Parkdale, the north side of Mount Hood bears a several-mile-long scar representing a previously undetected seismic fault that may still be active. The fault may also represent a future threat to the valley.
The last time the “Blue Ridge Fault” came to life was in response to a magnitude 6-7 earthquake near Mount Hood. The quake, occurring sometime during the last 12,000 years, resulted in a 6-foot vertical shift in one side of the fault, according to Ian Madin, chief scientist with the Oregon Department of Geology and Mineral Industries.
Madin will describe discovery of the fault, and other newly recognized aspects of the Hood River valley’s geology, at the upcoming monthly meeting of the Hood River Watershed Group. The 30-minute presentation is scheduled during the regular monthly meeting of the HRWG at 7 p.m. Oct. 23, at the OSU Extension Office meeting room (2990 Experiment Station Road in Hood River).
Much of this recent learning was made possible through the use of airborne LIDAR (light detection and ranging) equipment.
LIDAR is a technology that bounces laser light off the ground to uncover surface geology features. Madin’s recent work has uncovered the existence of many faults in the earth’s crust, including others near Mount Hood and others in Deschutes, Klamath and coastal counties. The work is being done by Madin and assorted partners to better understand the hazards that faults present to communities and infrastructure in Oregon.
Also during the meeting, the watershed group will be making free USGS topographic maps available to the public. Map sets are also available for pickup at the watershed group office at 3007 Experiment Station Road. The public is encouraged to attend this free education event.