Berkeley, California - Geology

Geology

Most of Berkeley lies on a rolling sedimentary plain that rises gently from sea level to the base of the Berkeley Hills. From there, the land rises dramatically. The highest peak along the ridge line above Berkeley is Grizzly Peak, elevation 1,754 feet (535 m). A number of small creeks run from the hills to the Bay through Berkeley: Cerrito, Codornices, Schoolhouse and Strawberry Creeks are the principal streams. Most of these are largely culverted once they reach the plain west of the hills.

The Berkeley Hills are part of the Pacific Coast Ranges, and run in a northwest–southeast alignment. In Berkeley, the hills consist mainly of a soft, crumbly rock with outcroppings of harder material of old (and extinct) volcanic origin. These rhyolite formations can be seen in several city parks and in the yards of a number of private residences. Indian Rock Park in the northeastern part of Berkeley near the Arlington/Marin Circle features a large example.

Berkeley is traversed by the Hayward Fault, a major branch of the San Andreas Fault to the west. No large earthquake has occurred on the Hayward Fault near Berkeley in historic times (except possibly in 1836), but seismologists warn about the geologic record of large temblors several times in the deeper past, and their current assessment is that a quake of 6.5 or greater is imminent, sometime within the next 30 years.

The 1868 Hayward earthquake did occur on the southern segment of the Hayward Fault in the vicinity of today's city of Hayward (hence, how the fault got its name). This quake destroyed the county seat of Alameda County then located in San Leandro and it subsequently moved to Oakland. It was strongly felt in San Francisco, causing major damage, and experienced by Samuel Clemens (Mark Twain). It was regarded as the "Great San Francisco Quake" prior to 1906. The quake produced a furrow in the ground along the fault line in Berkeley, across the grounds of the new State Asylum for the Deaf, Dumb and Blind then under construction, which was noted by one early University of California professor. Though no significant damage was reported to most of the few Berkeley buildings of the time, the 1868 quake did destroy the vulnerable adobe home of Domingo Peralta in north Berkeley.

Today, evidence of the Hayward Fault's "creeping" is visible at various locations in Berkeley. Cracked roadways, sharp jogs in streams, and springs mark the fault's path. However, since it cuts across the base of the hills, the creep is often concealed by or confused with slide activity. Some of the slide activity itself, however, results from movement on the Hayward Fault.

A notorious segment of the Hayward Fault runs lengthwise down the middle of Memorial Stadium at the mouth of Strawberry Canyon on the University of California campus. Photos and measurements show the movement of the fault through the stadium.