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Natural History of Angel Island

Angel Island is truly one of the Bay Area's most precious natural gems. The beautiful natural scenery and abundant wildlife make it a prime destination for bikers, campers and hikers.

General Description of the Island:

Angel Island is the largest island in San Francisco Bay, roughly "triangular" in shape, the island covers and area of approximately one square mile . Situated in the northern part of the bay, a half-mile channel named "Raccoon Strait," separates the island from the mainland. The deepest natural part of the bay, Raccoon Strait is second in depth only to the channel to the south, dredged deep to allow large ships to enter the bay. A coast guard lighthouse stands on Point Blunt, which extends out of the island roughly to the south, pointing directly to Treasure Island. Small coves and inlets pockmark the coast of the island, the largest of which, Ayala Cove, provides safe protected anchorage where boaters may stay overnight. Mount Caroline Livermore, named after the conservationist who led the fight to save the island from development, rises 781 feet above see level, making it the highest point on the island; the summit offers a full panoramic view of the bay. Two large ridges radiate from the central peek, forming a rough semicircle around Ayala Cove. These two ridges form the "backbone" of the island. Many trails crisscross the island, providing many great hiking opportunities, and majestic views of the Bay Area. Ten campsites provide opportunities for overnight excursions as well a picnic tables and eating areas for day visitors. In addition to the many trails, a five-mile road encircles the island, perfect for biking or easier walking, the road also offers many more spectacular views. (Angel Island 1-2)


The Geology of the Island:

Angel Island is essentially a large chunk of sedimentary sandstone. Pockets of sandstone are open all around the island, especially at Quarry Point, where large blocks of sandstone are unsullied by layers of shale. This sandstone was extensively quarried to provide building material for San Francisco. The island also contains traces of other rocks, igneous and metamorphic, the most common of which is "fourchite" found on the slopes of Mount Livermore. Many other rocks, including serpentine, appear in small outcropping, but a solid core of sandstone forms the foundation for the island (Angel Island 1-4).



The environment of Angel Island is similar to that of Marin County. The island is covered with perennially growing native grasses, as well as with European grasses (which are mostly annuals) that aggressively took root in the nineteenth century. Due to fires started by early Native Americans and wood chopping later, these grasslands extended over much of the island until there were hardly any trees left. But thanks to conservationist efforts, the natural forest and brush lands (including oak, bay manzanita, toyon, elderberry, chamise, sagebrush, coyote brush, many colorful varieties of wildflowers and as your guide might tell you, poison oak is everwhere) have largely recovered. Foreign varieties of trees and shrubs such as eucalyptus, Monterey pine, douglas fir, Monterey cypress, black locust, Australian tea trees, Portuguese cork oaks, palm trees and others recently introduced also thrive alongside native varieties (www.angel island.org).





Click this image to watch
an audio slideshow about the 2008 wildfire.
Click this image to watch
an audio slideshow about how Angel Island has recovered from the fire.

Click this image to watch
a movie about Angel Island's unique flora and fauna.


Wildlife is just as abundant and varied as the grassland, trees and shrubs. Deer and raccoons populate the interior of the island while seals and sea lions live right off the coast. Indeed, the seals are so numerous that if you spend time on the beach you are likely to see them popping their heads up.

The island is also a hub for bird life, including hummingbirds, flickers, hawks, owls, sea gulls, ducks, egrets, grebes, scoters, blue herons and kingfishers. Both brown and white pelican are abundant. These birds feed off salmon, striped bass and other fish that migrate to the ocean through Raccoon Strait (www.angel island.org).

And if you're as lucky as we are, you might even see a whale on the ferry ride over.


Conservationist Movement:

California residents have long valued Angel Island as a precious natural gem, but the effort to make it into a public park did not begin until the late 1940's when the importance of the immigration station declined. The conservatonist movement began to make headway when the government declared the island surplus property in 1947. In 1954, the California State Park Commission acquired almost 40 acres in the area near Ayala Cove. Four years later, the government set aside additional acreage in the same area, including the mountain, which was actually re-named Mount Caroline Livermore to honor a leader of the conservationist movement. Local groups continued to petition to increase the amount of the island set aside for park use, but they encountered serious setbacks when Angel Island was chosen as the site for a Nike missile base and radar control station in?. In 1963, the base was deactivated, and the island was no longer useful for military purposes. By the end of the same year, the government gave the entire island (with the exception of two coast guard stations on Point Blunt and Point Stuart) to the California State Park Commission (www.angelisland.org website).

Seth and Nilly

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Angel Island State Parks: www.cal-parks.ca.gov/travel/regions/bayarea/ai231/ai231_01.html


Angel Island Association. Angel Island. Tiburon: Angel Island Association, 1999