Located at a pullout off US 395 is a historical 'Beaver Board' that highlights the geological significance of Abert Rim. It reads:
Abert Rim
Oregon Geology
Behind you to the east is a steep cliff called Abert Rim, made of many layers of hardened lava flows. This 30-mile-long, 2,500-foot-high, steep cliff is an example of a fault scarp, produced over millenia by great blocks of rock tilting and moving along faults in this region where the earth's crust is thinning and stretching.
The fault that produced Abert Rim is on of many in the Basin and Range Province--ageologic region where rising blocks of crust (horsts) form mountain ranges, and sinking blocks of crust (grabens) create broad basins. The region spans about 300,000 square miles, including almost all of Nevada and parts of Oregon, Idaho, Utah, California, Arizona, and New Mexico.
Geologists believe the crustal movements contributing to Abert Rim's formation were probably accompanied by earthquakes of up to magnitude 6 to 6.5--they also believe the fault is still active.
Lake Abert, in the basin below Abert Rim, covers 63 square miles--but is only a remnant of Ice Age Lake Chewaucan, which once covered over 470 square miles. Lake Chewaucan's shorelines can still be seen lining Abert Rim's cliffs, far above the present shoreline.