Fire and Water: Recent mafic volcanism of the central Oregon Cascades

Fire and Water: Recent mafic volcanism of the central Oregon Cascades

Friday June 28, 9:00 AM to 5:00 PM

Trip Leader: Daniele McKay

Field trip description modified from Deligne and others, 2017

 The central Oregon Cascades have been shaped by geologically recent volcanism from hundreds of mafic vents located in a relatively small area. Activity in this region has produced extensive lava flows and surprisingly large tephra deposits. Lava flows from several mafic vents have interacted with ground or surface water and in many cases have altered the flows of rivers and streams. 

This field trip will explore recent mafic volcanism in the McKenzie Pass and Santiam Pass areas, with a focus on the Sand Mountain volcanic field. We will look at recent lava flows and tephra deposits, and at rivers, lakes, and groundwater that have been shaped by volcanic activity. We will also discuss hazards associated with mafic volcanic activity, including forest fires, disruption of water routes, and damage to infrastructure, agriculture, and tourism. 

COGS has extended an invitation for this field trip to the Geological Society of the Oregon Country (GSOC) in Portland. Normally all field trip participants must be COGS members in order to go on field tips, but this trip will also be open to GSOC members. This offers a great opportunity for meeting fellow geology enthusiasts and for building ties between our two organizations. 

This field trip is appropriate for all levels of geologic background, and all physical abilities. Total walking distance will be about 2 miles on generally flat trails. There will also be an optional boat ride at Clear Lake Resort. Please bring $5 in cash if you would like to participate in the boat excursion. Several field trip stops will require a Northwest Forest Pass or an equivalent public lands pass. Dress accordingly for changing weather at high elevations and bring a packed lunch, snacks, and water.

This field trip will depart from Sisters at 9:00 AM and will return to Sisters at about 5:00 PM. Please budget additional time for travel from Bend to Sisters and back. There will be a meet up location in Bend for arranging informal ridesharing. The field trip will be led by Daniele McKay.