Contra Costa County, California
Contra Costa County, California
Map
Location in the state of California
California’s location in the U.S.
Statistics
Founded
1850
Seat
Martinez
Largest city
Concord
Area
- Total
- Land
- Water
802 sq mi (2,077 km²)
720 sq mi (1,865 km²)
73 sq mi (189 km²),
Population
- (2000)
- Density
1,024,319
1,228/sq mi (474/km²)
Time zone
Pacific: UTC-8/-7
Website: www.co.contra-costa.ca.us
Contra Costa County (Spanish for "opposite
coast".[1]) is a primarily suburban county in
the San Francisco Bay Area of the U.S. state
of California. As of the 2006, the US Census
Bureau estimated it had a population of
1,024,319.[2] The county seat is Martinez.[3]
History
Pre-human
In prehistoric times, particularly the Miocene
epoch, portions of the landforms now in the
area (then marshy and grassy savanna) were
populated by a wide range of now extinct
mammals, known in modern times by the
fossil remains excavated in the southern part
of the county. These included pigs the size of
the modern rhinoceros and rhinoceri the size
of modern pigs. In the northern part of the
county, significant coal and sand deposits
were formed in even earlier geologic eras.
Other areas of the county have ridges expos-
ing ancient but intact (not fossilized) sea-
shells, embedded in sandstone layers altern-
ating with limestone. Layers of volcanic ash
ejected from geologically recent but now ex-
tinct volcanos, compacted and now tilted by
compressive forces, may be seen at the site
of some road excavations. This county is an
agglomeration of several distinct geologic
terranes, as is most of the greater San Fran-
cisco Bay Area, which is one of the most geo-
logically complex regions in the world. The
great local mountain Mount Diablo has been
formed and continues to be elevated by com-
pressive forces resulting from the action of
plate tectonics and at its upper reaches
presents ancient seabed shale rock scraped
from distant sedimentation locations and ac-
cumulated and lifted by these great forces.
Younger deposits at middle al