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Geo info
Geology and landforms
Multiple terrains
The area is well known worldwide for the complexity of its landforms, the region
being composed of at least six terrains (continental, seabed, or island arc
fragments with distinct characteristics) pushed together over millions of years
by the forces of plate tectonics. As a consequence, many types of rock and soil
are found in the region. Formations include the sedementry rocks of sandstone,
limestone, and shale in uplifted seabeds, metamorphic serpentine rock, coal
deposits, and igneous forms as the basalt flows and ash deposits of extinct
volcanos. Pleistocene-era fossils of mammals are abundantly present in some
locations.
Vertical relief
The region has considerable vertical relief in its landscapes that are not in
the alluvial plains leading to the bay or in inland valleys. In combination with
the extensive water regions this has forced the fragmented development of urban
and suburban regions and has led to extensive building on poor soils in the
limited flatland areas and considerable expense in connecting the various
subregions with roads, tunnels, and bridges.
Several mountains are associated with some of the many ridge and hill structures
created by compressive forces between the Pacific Plate and the North American
plate. These provide spectacular views (in appropriate weather) of large
portions of the Bay Area and include Marin County's Mount Tamalpais at 2,571
feet (784 metres). Contra Costa County's Mount Diablo at 3,849 feet (1,173
metres), Alameda County's Mission Peak at 2,517 feet (767 m), and Santa Clara
County's Mount Hamilton at 4,213 ft (1,284 m), the latter with significant
astronomical studies performed at its crowning Lick Observatory.
The three major ridge structures are all roughly parallel to the major
faultlines:
The Coast Range, which is the spine of the San Francisco Peninsula and Marin
County
The Oakland-Berkeley Hills and their southern ridgeline extension through
Mission Peak.
The Diablo Range, containing Mount Diablo and Mount Hamilton.
Rivers and bodies of water
San Francisco Bay
San Pablo Bay
Suisun Bay
Sacramento River
San Joaquin River
San Joaquin-Sacramento Delta
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