Most avid birders might be more interested in the incredible diversity of avian species which visit and inhabit the Bay Area than in the rocks beneath. But the two are part of the same story: geologic diversity typically underlies ecologically diverse areas, and the bedrock beneath our beautiful lush areas governs unseen, determining crucial life conditions like how water moves through an area, how the composition of soils can support or restrict plant growth in an area and the elevation and slope at which vegetation grows. The uniqueness of the geologic setting beneath Marin makes for some pretty interesting conditions for life, which supports some very rare endemic species of plants and animals.  Serpentine is very erodible and as it weathers, it becomes a thin, rocky soil layer, rich only in nickel, chromium, and cobalt, heavy metals which choke plant growth and inhibit organic matter build up in the soil.…