San Francisco, California - Geography

Geography

San Francisco is located on the West Coast of the United States at the north end of the San Francisco Peninsula and includes significant stretches of the Pacific Ocean and San Francisco Bay within its boundaries. Several islands—Alcatraz, Treasure Island and the adjacent Yerba Buena Island, and small portions of Alameda Island, Red Rock Island, and Angel Island—are part of the city. Also included are the uninhabited Farallon Islands, 27 miles (43 km) offshore in the Pacific Ocean. The mainland within the city limits roughly forms a "seven-by-seven-mile square," a common local colloquialism referring to the city's shape, though its total area, including water, is nearly 232 square miles (600 km2).

San Francisco is famous for its hills. There are more than 50 hills within city limits. Some neighborhoods are named after the hill on which they are situated, including Nob Hill, Potrero Hill, and Russian Hill. Near the geographic center of the city, southwest of the downtown area, are a series of less densely populated hills. Twin Peaks, a pair of hills forming one of the city's highest points, forms a popular overlook spot. San Francisco's tallest hill, Mount Davidson, is 925 feet (282 m) high and is capped with a 103-foot (31 m) tall cross built in 1934. Dominating this area is Sutro Tower, a large red and white radio and television transmission tower.

The nearby San Andreas and Hayward Faults are responsible for much earthquake activity, although neither physically passes through the city itself. The San Andreas Fault caused the earthquakes in 1906 and 1989. Minor earthquakes occur on a regular basis. The threat of major earthquakes plays a large role in the city's infrastructure development. The city constructed an auxiliary water supply system and has repeatedly upgraded its building codes, requiring retrofits for older buildings and higher engineering standards for new construction. However, there are still thousands of smaller buildings that remain vulnerable to quake damage.

San Francisco's shoreline has grown beyond its natural limits. Entire neighborhoods such as the Marina, Mission Bay, and Hunters Point, as well as large sections of the Embarcadero, sit on areas of landfill. Treasure Island was constructed from material dredged from the bay as well as material resulting from tunneling through Yerba Buena Island during the construction of the Bay Bridge. Such land tends to be unstable during earthquakes. The resulting liquefaction causes extensive damage to property built upon it, as was evidenced in the Marina district during the 1989 Loma Prieta earthquake. Most of the city's natural watercourses, such as Islais Creek and Mission Creek, have been culverted and built over, although the Public Utilities Commission is studying proposals to daylight or restore some creeks.