Workers digging the new fourth bore of the Caldecott Tunnel are getting a once-in-a-lifetime view of one of the defining features of the East Bay: the range of hills that runs from San Pablo Bay south to Fremont. By visiting just a few accessible sites aboveground, you can find clues that tell the story of how these hills rose from their humble origins as deep ocean sediments and volcanic flows to the iconic fault-riddled hillsides of today.
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