|Drake's Beach, with outcrops of Purisima Formation that reminded early sailors of Dover.|
For many millions of years, oceanic crust and exotic terranes were carried eastward towards the continent, only to be forced beneath the edge of North America (subducted). Eventually the source of oceanic crust, the East Pacific spreading center, made contact with the convergent margin and subduction ended. Because of the relative motion of the two plate edges, a new fault system developed, the San Andreas, and a portion of Southern California began to move northwestward along the new fault. Such zones that divide crustal plates from one another are called transform boundaries. Granitic rock that had formed as part of the Sierra Nevada Batholith was sliced off from the south end of the province and was carried north several hundred miles (see below). The displaced granitic rocks are referred to as the Salinian Block.
Drake's Estero is an interesting feature. The branching arms of the bay suggest that it is a submerged river valley. The shallow water has proven to be a good spot for oyster farming, and the 80 year old business is embroiled in a battle with the park service over land-use issues.
|Source: USGS (http://pubs.usgs.gov/of/2005/1127/)|
around 140 days a year. Winds are nasty (highest recorded was 133 mph), and the temperature generally hovers between 50 and 60 degrees Fahrenheit all year.
|Steps leading to the Point Reyes Lighthouse|
|Point Reyes Lighthouse, constructed in 1870|