Tomales Bay begins where the San Andreas Fault descends below
the sea just 40 miles north of San Francisco Bay. Tomales
Bay ends where wave action from the open ocean wraps around
Tomales Point and forms Sand Point at the mouth of the bay,
near Lawson's Landing. The mouth of the bay is thus one of
its narrowest points, making the waters of the bay semi-enclosed.
The bay is a meeting place of freshwater and salt water. Freshwater
flows into Tomales Bay from Olema, Lagunitas, and Walker Creek.
Collectively, these creeeks drain 219 square miles of land.
Tidal influence brings saline waters into the Tomales Bay
from Bodega Bay and the open ocean. Tomales Bay is thus an
estuarine environment, one of fluctuating salinities.
 Numerous
coastal wetlands lie along the bay's variable shoreline. Rocky
along much of its northwestern reach and sandy along its northeastern
reach, the shore becomes mud-rich at the southern end of the
bay. There, Olema and Lagunitas Creeks drain into Tomales
Bay, bringing sediments in from the surrounding hills.
In addition to the extensive intertidal
areas where organisms are exposed to air and direct sunlight,
the bay reaches depths of 17 meters, creating subtidal habitats
that receive very little light penetration. The effects of
tidal flow and variations in salinity further complicate the
physical structure of the bay's habitats.
 This
structural diversity of the bay provides conditions suitable
to a great diversity of life forms. Archaic worms live
in the deep, lightless mud. Abundant plankton drift throughout
its waters, providing food for over 150 species of fishes.
Over 200 species of algae can be found along bay shores
and 163 species of birds make the bay their home or resting
place on migration.
Tomales Bay provides significant habitat
for endangered Coho Salmon, is an important area of oyster
and clam aquaculture, and hosts recreational fishing and kayaking.
Not only is the bay the meeting place of tectonic plates moving
against one another along the San Andreas fault - it is a
dynamic environment where all major forms of life interact
in living communities.
Click
here for more information on visiting Tomales Bay and
surrounding areas.
Click
here for a list of facts on Tomales Bay's watershed.
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