Basalt Ring Formations of the Columbia River Plateau

Skye Schillhammer, Eastern Washington University
Carly Sorensen, Eastern Washington University
Ted Uecker, Eastern Washington University
Natasha Garland, Eastern Washington University


Unusual basalt ring formations are located about 6 miles north of Odessa, WA as part of the expansive Columbia River Basalt Group. There are over 100 crater-like structures that range in size from 50-500 meters in diameter and span a 60 kilometer area of the channeled scablands. These structures are enigmatic due to the erosion of surficial features by the Missoula Floods, and due to their association with a magnetic anomaly as evidenced by an aerial geophysical survey. Since the 1970s, multiple geologists have proposed conflicting formational mechanisms for the rings, including hydrothermal explosions and sag flows. Over the past decade many more data sets and studies have been published on the CRBG members and we use these data to re-evaluate past hypotheses for these unique structural features. Our research team measured the stratigraphy of the craters and the surrounding rock and collected samples for XRF analysis. The data suggests that these structures formed by auto-intrusions of the Roza member of the Wanapum formation.