On Basaltic Andesites: The Dominant Lava Type of the Central Oregon High Cascades

Visiting Scholar Presentation

Alyssa Smith

Portland State University

Watch Alyssa's recorded presentation

Emily Johnson

U.S. Geological Survey

The central Oregon Cascades are unusual when compared to the rest of the Cascade volcanic range. This region of the Cascades is dominated by basaltic andesite, a volcanic rock of intermediate composition between basalt and andesite. Basaltic andesite has been the most prevalent type of lava erupted in the central Oregon Cascades for the past ~8 million years. It can be seen in many of the prominent skyline peaks of central Oregon, including North Sister, Black Butte, Mt. Washington, and Three Fingered Jack.

Despite the overwhelming dominance of basaltic andesite in this region, the chemical variability of these lavas has not been well documented. Are they related to basaltic lavas that have been erupted in the region? What geologic processes are responsible for generating and sustaining large volumes of basaltic andesite volcanism in this portion of the Cascades? Join Alyssa Smith, PhD candidate at Portland State University, and Emily Johnson, USGS Research Geologist at the Cascades Volcano Observatory, for an exploration of geochemistry and volcanic history of the central Oregon Cascades.

COGS talk are free and open to the public -- all are welcome! This talk is co-hosted by the Sisters Science Club and will be held in Sisters:

Wednesday, July 10

7:00 pm

The Lodge in Sisters 

411 E. Carpenter Lane

COGS presentations are also live-streamed through Zoom. Clink on the registration link at the top of this page to register for the Zoom meeting.