We spent the evening a few towns over, in Crockett, eating dinner on a stone patio a hundred feet above the Carquinez Strait.
The Strait is a narrow channel, only a mile or so wide, where the waters of the Sacramento and San Joaquin rivers drain through the Coast Ranges on their way to the Golden Gate. The great Pleistocene Sacramento River flowed through the strait before the ending Ice Age pushed the coast east of what are now the Farallones, filling the broad, grassy valley we know as the Bay.
A couple years ago sitting on the porch of a cabin outside Flagstaff, I watched the slopes of the San Francisco Peaks, mentally filling in the obvious gap at the summit where an ancient explosion tore off several thousand feet of mountain. A little geological knowledge is a dangerous thing. Tonight I sat, nursing a draft, and imagined that was fresh water below, sabertooth cats and shovel-tuskers stalking the shores.