Geography and landscapes California
California, 3rd State by area after Alaska and Texas, covers 424 km². It is bordered to the north by Oregon, to the west by the Pacific Ocean (over 000 km), to the east by Nevada and to the south by Mexico.
Coastal chains from the West, ridges, small valleys and rivers outline its landscape. Over a length of 800 km and a width ranging from 80 to 120 km, the coastal chains (rich in silver, non-ferrous metals, oil and hydroelectric potential) divide to make way for the San Francisco Bay. The rivers of the western Sierra Nevada ("snowy chain" in Spanish) and the plains of the Central Valley thread their way through to join the Pacific.
La Central Valley, which stretches from the coastal ranges in the west to the Sierra Nevada in the east, is bounded on the north by the Sacramento River and on the south by the San Joaquin River. This immense valley is one of the richest and most varied agricultural areas in the country.
East of the Central Valley, the Sierra Nevada offers magnificent canyons formed by erosion. While walking in the national parks of Yosemite, Sequoia and Canyon Kings, we take advantage of these granite landscapes.
Further south is Mexico, with the United Forests (86 m below sea level). Finally, culminating at more than 1 m of altitude, the Mojave desert is the most irrigated and the highest.
Waiting for the Big One
California is a unstable tectonic region ; seismic phenomena are numerous there. The main culprit is the San Andreas fault, a fracture in the earth's crust, which crosses the Pacific Ocean and crisscrosses under the state, between the Gulf of California and northern San Francisco. This city holds the sad record for earthquakes.
The most dramatically famous remains that of 1906: the fire triggered by the earthquake destroyed 4 / 5ths of the city. In 1989, a new earthquake (7,1 on the Richter scale) this time caused the collapse of the Bay Bridge but ultimately caused few victims in the city thanks to the effectiveness of the new anti-seismic standards.
In 2019, southern California was hit by a magnitude 7,1 earthquake, the largest since 1999. While it did little damage in this sparsely populated region, it rekindled fears of the Big One. This cataclysmic earthquake (specialists speak of an intensity of 8,5 on the Richter scale) is expected to shake the region within 40 years and cause significant devastation.
Until now, we only talked about the San Andreas fault, which causes one or two tremors of magnitude 2 every day and which, according to specialists, will be at the origin of the disaster. But for some time, scientists have been interested in another fault, named Hayward, near Berkeley and San Jose. It crosses Oakland, a very populated region that is poorly prepared for earthquake risks.
Every evening, on TV, the earthquake report details the tremors of the day.
And every year, in October, a big dress rehearsal is organized in schools, buildings and businesses in the region: The Great Shake Out. It must be said that the region records no less than 17 tremors per year ...