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Concept
Île Anacapa
Résumé
Anacapa Island (Chumash: Anyapax, meaning "mirage, illusion") is a small volcanic island located about off the coast of Port Hueneme, California, in Ventura County. The island is composed of a series of narrow islets long, oriented generally east–west and east of Santa Cruz Island. The three main islets, East, Middle and West Anacapa, are collectively known as The Anacapas by some authors. All three islets have precipitous cliffs, dropping off steeply into the sea.
Anacapa is the smallest of the northern islands of the Channel Islands archipelago, and is within the Channel Islands National Park. It is across the Santa Barbara Channel from the nearest point on the mainland. It lies southwest of the city of Ventura.
Along with Santa Barbara Island, Anacapa was formed by volcanic eruptions between 19 and 15 million years ago. These eruptions are believed to have been caused by thinning of ocean crust as the block containing the northern Channel Islands and Santa Monica mountains was rotated clockwise by the transverse motion of the Pacific and North American plates. Lava from these eruptions can be found across the region, and in depths of up to . The rocks that make up Anacapa are composed of lava, breccias, volcanic ash and cinders.
Erosion has heavily weathered the lava formations of Anacapa, and wave action caused the island to split into three islets in recent prehistoric times. The islets display a wide variety of erosional features including sea arches, sea caves, stacks, wave-cut platforms, surge channels and blowholes.
West Anacapa is the largest and highest islet, rising to an altitude of at Vela Peak, also known as Summit Peak 2. East and Middle Anacapa have fairly level areas at their tops. Middle Island reaches an altitude of and East Island is at its highest point. All three islands total , or about .
East Island's most notable natural feature is Arch Rock, a -high natural bridge.
As recently as the end of the last ice age (about 10,000 years ago), sea levels as much as lower meant that the four northern Channel Islands were part of a single large island (dubbed "Santa Rosae") that lay about off the California coast.
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