Rings in the Basalt – The Mysterious Origins of the Odessa Craters

The Odessa Craters are a series of ring-like structures within the Columbia River Basalt that are scattered throughout the channeled scablands in Eastern Washington. There are over 100 ring-structures located North and East of Odessa, each one being 50-500 m wide (Hodges, 1977). The basaltic ring structures are a great destination for tourists and hikers, but they have also intrigued many geologists and are constantly being explored in hopes to find out how these amazing structures formed. Though nobody is sure exactly how the craters formed, it is clear that the cataclysmic Missoula Floods that carved out the scablands exposed these unique features.
Studied craters either had a central mound, central depression or were fairly planar. Figure 1 shows an example of Amphitheater Crater and Figure 2 shows the distribution of major "Odessa Craters". While looking at the basaltic layers of these structures, auto-intrusive (or intruding into the same unit) dikes were found. A model (Figure 3) called the “sag flow out” was created (McKee and Stradling, 1970). This model was slightly modified by Keszthelyi and Jaeger (2013), but still describing the formations by lava-flow dynamics. To confirm this the Structural Geology (GEOL 431) classes at Eastern Washington University worked with the BLM to sample and analyze the tilted basalt (dikes) and the surrounding non-tilted basalt and they are all part of the Roza Member of the Wanapum Basalt, showing that they formed associated with the lava flow (Figure 4). What makes the craters unique is that the surface was washed away by the Missoula Floods revealing the Odessa Craters.
These intriguing structures have had geologists questioning its complicated history and several theories have been made about the process that produced the Odessa Craters. There is still no proven explanation as to how these got here. The investigation on the Odessa Craters helps provide new information not only about these craters but other areas in the world that have similar structures. There are even locations on mars that have a relevance to the information found at the Odessa Craters.