San Gabriel Mountains 130 miles to
the northwest. These mountains, lying on opposite sides of the San Andreas
Fault, provide part of the convincing evidence indicating a lateral land
movement along the fault of over 130 miles.
Aigodones Dunes: Also known
as the Imperial Sand Dunes, this large area of sand, averaging 5 miles in width
and 45 miles in length, is located east of El Centro. Source of the sand is
believed to be from the shores of ancient Lake Cahuilla.
Lake
Cahuilla: Several times during the past 2,300 years, the Colorado River
changed course between the Gulf of California (into which it empties today) and
the Salton Sink. Each time the river emptied into the Salton Sink, an inland
freshwater lake (known today as Lake Cahuilla) formed before the rising silt
and debris reversed the rivers course back to the Gulf. The most recent Lake
Cahuilla covered much of the Imperial and Coachella Valleys as late as
1500.
Salton Sea: The current lake was created between 1905-1907
when the Colorado River broke through an irrigation canal system. The lake
level is maintained today by water brought in for agriculture.
DESERT
GEOLOGIC FEATURES
Sand Dunes: Sand dunes are not widespread
in the CDCA but many areas have one or more groups of dunes. They have
developed where wind patterns have a source of sand which is transported and
then accumulated. Much of the sand accumulated by wind in the CDCA was created
by lakes and streams which existed during the last glacial times (2 million to
10,000 years ago).
Alluvial Fans: These delta-shaped deposits of
sediment radiate out from canyon mouths throughout the CDCA. Occurring in an
arid climate where there is insufficient water flow to completely remove rock
sediment, the rock debris accumulates around the bases of mountain
ranges.
Alluvial fans attain their greatest size in the Basin and Range
Province where ongoing uplifting is creating higher mountain masses than in the
rest of the CDCA. Good examples of large fans can be seen in Panamint Valley
where they extend completely along the base of the Panamint and Argus Ranges.
These fans often merge with one another and form a broad, sloping plain called
a bajada (meaning lower slope). These bajadas are less steep than the
mountains, and make up a common landform in the desert.
Desert
Pavement: These areas of flat, rock mosaics occur throughout the CDCA. They
typically occur on flat-topped divides between desert washes. They attain their
greatest extent in the Colorado Desert Province of the CDCA where in recent
geologic history the land has been more stable with less uplifting to interrupt
the process of desert pavement formation.
Desert Varnish: In many
areas of the CDCA, rock out-crops have a dark brown-black color. Called desert
varnish, it forms in stable rock areas where the rocks have time (1,000 plus
years) to form a natural coating of clay, iron, and manganese oxides. This
darkened appearance of rock surfaces can form on individual rocks and on large
bedrock exposures.
Relicted Features: Throughout the CDCA are
geologic features which were produced under former climatic conditions. Most of
these features were created when the |
climate in the CDCA was much cooler
and wetter than today during the last glacial period. Some of the more common
fossil landform features which can be observed in the CDCA include: fossil
falls, lake shorelines, stream deltas, saline deposits. stream channels, sand
bars, and terraces.
MINING IN THE CDCA
The first miners in
the desert were Indians, followed by Spanish explorers and American
frontiersmen. Since the 19th century, over 18 different metallic and 27
nonmetallic minerals have been mined in the CDCA. These minerals include: gold,
iron, lead, mercury, silver, tungsten, uranium, zinc, boron, gemstones, gypsum,
limestone, mica, potash, pumice, salts, sand and gravel, marble, and talc. Many
mining operations, large and small, have and are occurring in the CDCA. Today,
there is estimated to be in excess of 5,000 mines currently in operation. There
are many famous mines which have operated in the CDCA.
Cerro
Gordo: Located high on the crest of the Inyo Mountains east of Lone Pine,
this area is accessible on a county-maintained road starting at Keeler. First
operated in 1860, it was California's largest silver producing
mine.
Panamint City: A famous silver camp in the Panamint Range,
40 miles north of Trona, the camp can be reached by traveling up steep and
rugged Surprise Canyon. Major production was from 1873-1876 and a
sixty-foot-high smelter smokestack still remains. Additional silver production
is still occurring today.
Vulcan Iron Mine: In the southern
Providence Mountains, iron ores were mined from 1942-1947. Today, a large open
pit remains.
Yellow Aster: This famous California gold mine was
in operation between 1896 and 1918. Other ores mined in this area along Highway
395 at Red Mountain were silver and tungsten.
Calico: From 1881
until 1896, silver was produced from this mine in the Calico Mountains,
northeast of Barstow.
Picacho Mine: During 1904-1910, over $2
million worth of gold was reportedly extracted from this mine, when gold sold
for an average of $35 per ounce. First mined in the 1880's, Picacho Mine was
shutdown in the 1930's due to the low price of gold ($22 per ounce). Most of
these mines were never reopened after the war effort halted gold production.
The Picacho Mill was built along the Colorado River to process the gold ore
produced from the Picacho Mine.
U.S. Gypsum Mine: Located in the
Fish Creek Mountains adjacent to Anza-Borrego Desert State Park, the gypsum
mine was worked in 1922 by various operators. The mine was bought by U.S.
Gypsum Company in 1945 and is still in production.
Eagle
Mountain: Small gold mining claims were worked in this area of the
southeastern Eagle Mountains at the turn of the century until bought out by
Kaiser Steel Corporation. Since then, the Eagle Mountain Mine has become the
largest mine on the west coast.
Midland Gypsum Mining District:
Mines in this area of the Little Maria Mountains were very active in the
1940's. However, the mines became idle and the old town of Midland was closed
in the late 1950's due to lack of water. |