Page 43 - Super Earth Encyclopedia
P. 43
CREEPING CRUST
SAN ANDREAS FAULT
Earth’s rocky shell is full of fractures called faults.
Many of these are small, local features, but the
San Andreas Fault in California is a huge rip in the planet’s
crust that marks a sliding boundary between two of
Earth’s biggest tectonic plates. The Pacific Plate to the
west is creeping north past the North American Plate,
taking coastal California with it. In some places, small,
frequent movements cause minor tremors, but other
sections of the fault lock together, building up tension
as the plates keep moving. Eventually, the rock gives
way, and the shock causes a big earthquake such as the
one that devastated the city of San Francisco in 1906.
AT A GLANCE
• LOCATION California
• EXTENT More than 800 miles (1,300 km)
long and over 10 miles (16 km) deep
• TYPE OF FORMATION Transform fault
in which two tectonic plates slide past
each other
• EARTHQUAKE RISK High
41 FORMIDABLE FORMATIONS
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