Neenach Volcano

Neenach Volcano is an extinct Miocene volcano in the Coastal Ranges of California. After formation, the volcanic field was split by a fault in the San Andreas Fault Zone, and over the last 23 million years, the two halves of the volcano have moved about 195 miles apart.

The correlation of the two portions, now called the Pinnacles and Neenach volcanic formations, is significant; this correlation has become a “classic example” of plate tectonics for the scientific community. Ten rock types with nearly identical field, petrographic, and chemical characteristics are present in each formation in essentially the same stratigraphic order. This provides ample evidence for the correlation and interpreted movement along the San Andreas Fault.