Information AboutSeal Rock |
| CATEGORIES ABOUT SEAL ROCK | |
| geology of california | |
| landmarks in san francisco | |
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Seal Rock is a large and prominent rock found offshore at the North end of the Ocean Beach in San Francisco . It is named for the population of Steller's Sea Lion s (Eumetopias jubatus) who sun themselves on the rock, and are often colloquially called "seals". GEOLOGY AND HISTORY OF THE AREA Near the end of the last Ice Age , this part of the coastline was thought to be between eight and twenty five miles westward of its current position - around five thousand years ago, with the melting of the ice, the sea level rose to its current level. The coastal features found here today were formed by the actions of waves, wind, and the movement of sand. The geology of this part of the coastline of San Francisco consists of steep rocky cliffs which are punctuated by narrow sandy pocket beaches found at the north end of the city and long sandy stretches at Ocean Beach and Fort Funston to the south. The local features, and indeed the entire San Francisco Peninsula , come from the northern aspect of the Santa Cruz Mountains . Before the urban development seen today the area landward of Ocean Beach consisted of barren sand fields inland to Twin Peaks . The first known map of the area, dating from 1852, was made by the U.S. Coast And Geodetic Survey and describes the coastline here as being entirely unaltered by humans. The geologic layers beneath Ocean Beach, starting from the top (i.e. the youngest) are:
The Colma and Merced Formations consist generally of poorly-sorted sandy deposits and were probably deposited during some earlier period of greater sea levels. The Colma Formation is found under the dune sands and also extends inland. SEE ALSO 49-Mile Scenic Drive EXTERNAL LINKS
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