lanes, prompted President Theodore Roosevelt to sign Executive Order No. 1043 in 1909, creating the Farallon Reservation to protect the chain's northern islands. This was expanded to the other islands in 1969 when it became a national wildlife refuge. In 1981, Congress designated the Gulf of the Farallones National Marine Sanctuary, which spanned 1,279 square miles (3,313 square kilometers; 966 square nautical miles) of water surrounding the islands. This sanctuary protected open ocean, nearshore tidal flats, rocky intertidal areas, estuarine wetlands, subtidal reefs, and coastal beaches within its boundaries. In 2015, the sanctuary was enlarged north and west of the original boundary, partially surrounding Cordell Bank National Marine Sanctuary, to encompass 3,295 square miles (8,534 square kilometers; 2,488 square nautical miles), and the name was changed to Greater Farallones National Marine Sanctuary. The sanctuary is contiguous with both the Cordell Bank sanctuary and another sanctuary to the south, Monterey Bay National Marine Sanctuary. The islands are managed by the United States Fish and Wildlife Service, in conjunction with the Marin-based Point Blue Conservation Science (formerly Point Reyes Bird Observatory). The islands are currently the subject of long term ecological research. The Farallones are closed to the public, although birders and wildlife enthusiasts can approach them on whale watching boats and the sail-training vessel Seaward out of Sausalito. Geology The Farallon Islands are outcroppings of the Salinian Block, a vast geologic province of granitic continental crust sharing its origins with the core of the Sierra Nevada Mountains. The block was rifted off far to the south of its present position and moved north with the Pacific Plate on which the islands rest. Other nearby examples of the Salinian Block include the Point Reyes Peninsula and Bodega Head. The San Andreas Fault, marking a boundary zone between the Pacific and North American Plates, passes a few miles east of the islands. The ancient Farallon Plate is named after the islands. Geography Overview The islands string northwestward from Southeast Farallon Island for . Their total land area is . The islands were initially exploited for bird eggs and fur seal skins, then used as a lighthouse station and a radio station. They have been protected in the Farallon Islands National Wildlife Refuge, first established in 1909 with the Southeast Farallons added in 1969, and contain the largest seabird colony in the U.S. outside of Alaska and Hawaii. The islands are part of the