COGS is a Central Oregon-based non-profit organization promoting a greater awareness and understanding of the geological sciences through technical presentations, outreach, and field trips


Upcoming Presentation

Please click HERE to register for this Zoom Presentation

Tuesday, November 23

6:45PM "Doors Open", 7:00PM Presentation

 Rebecca Dorsey

Department of Earth Sciences, University of Oregon

Tectonic evolution of the Cascadia margin in southwest Oregon during the past 55 million years

Sedimentary and volcanic rocks in southwest Oregon record a complex history of subduction, accretion, sedimentation, rotation, and uplift at the Cascadia convergent margin over the past ~55 million years. This presentation will integrate knowledge from legacy datasets with ongoing studies to share insights into tectonic events and processes that have shaped the Cascadia forearc region through Cenozoic time. The 54 to 48 Ma Umpqua Group contains conglomerate, sandstone, turbidites, shale and deltaic deposits that filled a large syn-collisional basin with detritus shed from the Klamath Mountains. The Tyee Formation (~47 to 42 Ma) is a thick package of micaceous fluvial to deltaic deposits and marine turbidites that prograded north through western Oregon. Stratigraphic and petrologic studies suggest that the Tyee Formation was derived from the eroding Klamath Mountains, not western Idaho. The late Eocene to early Oligocene Fisher and Eugene formations (~40 to 30 Ma) and equivalent units in the Coos Bay area record deposition of sediments and tuffs in a large forearc basin situated between the early Cascades volcanic arc and the Cascadia subduction zone. Starting ~30 Ma the forearc basin was uplifted, inverted, and folded to form angular unconformities in the Coos Bay area. This marks the change to a structurally fragmented forearc region characterized by regional uplift and erosion in the Oregon Coast Range that continues to the present day.

Geoscience Events & Activities by Others

2021 Oregon Lakes Association Online Seminar Series

Wednesday Nov 3 (2:30-5pm), Nov 10 (2:30-5pm) and Dec 1 (3-5pm)

Click HERE for details on the Online Zoom meetings

Tuesday November 9th at 10 AM (PST)

Geoscience Research in National parks: A Welcome and a How-to


American Geosciences Institute (AGI)

Chick HERE for details and webinar registration

Friday November 12th @ 7:30 PM
Ice Age Floods Geological Trail
Dr. Scott Burns
Click HERE for Zoom registration

Thursday November 18th @ 7:00 PM

Busting Myths About One of the Largest Volcanic Systems in the World - The Top 10 Misconceptions about Yellowstone Volcanism

By Michael Poland, USGS Geophysicist and Scientist-in-charge, Yellowstone Volcano Observatory

Click HERE for Details & link to presentation