Geologists believe that the west boundary of this ancient seaway was the uplifted rocks of the Franciscan Assemblage that today make up the Coast Ranges, and the east boundary was a chain of ancient volcanoes located where the Sierra Nevada is today.
The west boundary of this ancient seaway was the uplifted rocks of the Franciscan Assemblage that today make up the Coast Ranges. This is what geologists believe. The east boundary was a chain of ancient volcanoes. These ancient volcanoes were located. The Sierra Nevada is today.