Anacapa Island is the second smallest of the islands making up Channel Islands National Park off the California coast. Anacapa is actually composed of three individual islets referred to as East, Middle and West Anacapa. The three islets are separated by narrow channels that have been cut into the volcanic rock by erosional forces.
Anacapa sits at the western end of the island chain it forms with Santa Cruz, Santa Rosa, and San Miguel Islands. Looking at a relief map of the California coast in this area, you will notice that a gently curving line can be drawn from the westernmost tip of San Miguel Island to the eastern tip of Griffith Park near downtown Los Angeles. The Santa Monica Mountains are the geological feature beneath this line from where it crosses the coastline, until the end in Griffith Park. The line also signifies that the east/west trending chain of the northern Channel Islands is simply an extension of the Santa Monica Mountains out into the ocean. If you look closely at today’s photo, you may notice a dark shape beyond the island, which may appear to be a fog or cloud bank, but is in fact the bulk of the Santa Monica Mountains rising to the east of Anacapa in the direction of the rising sun.
The Santa Monica Mountains and their extension into the Channel Islands are a bit of a geological oddity in California. If you look at a wider scale relief map of California, notice the location of the mountain ranges within the state. You may notice that most of these ranges run largely north to south down the length of the state, but if you look closely at the area around Los Angeles, you may notice several mountain ranges that run east to west, instead of north to south, and these include the Santa Monica Mountains, and their extension into the northern Channel Islands.
How is it that the mountains in this part of California run at an almost 90 degree angle to the rest of the mountains in the state? As with so much of the geology of the Earth, plate tectonics is the answer. Up until about 20 million years ago, the North American plate on which California and the rest of the continent of North America rides was moving westward, while an oceanic plate was moving eastward and diving under it. Then the northwesterly moving Pacific plate, which today lies beneath most of the northern Pacific Ocean, came up along the coast and caught hold of a small tip of the North American plate. As the Pacific plate continued on its way, it took a chunk of what is now southern California with it, twisting in a clockwise direction. Everything on that chunk of the North American plate got twisted right along with it, including the mountains. As a result, once the two plate disentangled, we had a chunk of the future California sitting at about a 90 degree angle from where it had been originally. The results we see today are the mountain ranges known as the Transverse Ranges in southern California.
Eighteen different ranges are included in southern California’s Transverse Ranges; among them are the Santa Ynez, San Rafael, Topatopa, Tehachapi, San Gabriel, San Bernardino, Santa Monica, and Santa Susana Mountains.
You can find an animation of the creation of the Transverse Ranges at: http://emvc.geol.ucsb.edu/1_DownloadPage/Download_Page.html#TransverseRanges
This photo was taken with a Canon EF28-135 mm f/3.5-5.6 lens zoomed to 75 mm on a Canon EOS 10D. The exposure was set to 1/100 sec at f/8.0 and ISO 400.