Last week I wrote about how geological changes along the California coast may have resulted in the odd distribution of Torrey Pines into two disjunct populations separated by about 175 miles of open ocean. The movement of the Torrey Pines on Santa Rosa Island was part of the movement of a larger block of the Earth's crust that was part of the North American tectonic plate.
As the Pacific plate came into contact with North America, it eventually caused what is now Baja California to break away from the North American plate and be transferred onto the Pacific Plate. Once this happened, the future Baja California began moving northwestward on the Paciic Plate. This movement opened what is now the Gulf of California between Baja California and mainland Mexico, and it radically altered the layout of much of southern California between modern day San Diego and Santa Barbara, and eastward into California.
Prior to this geological upheaval, millions of years of geological activity between the North American plate and a different oceanic plate had created a series of north-south running mountain ranges along the western edge of North America. These mountain ranges were separated by valleys that also trended north and south. But when the northern end of the newly capture Baja California block crashed into a chunk of it's former plate that was deeply rooted in the continental plate, the northern end of this chunk got stuck against North America, and this resulted in a clockwise rotation of this chunk through an arc of somewhere between 90 and 110 degrees from its original position. This chunk, along with other portions of the westernmost edge of North America, was torn away and transferred onto the Pacific Plate.
The rotated chunk, now know as the Transverse Ranges, became a series for roughly east-west running mountain chains slicing through what is now southern California. It happens that the northern Channel Islands of San Miguel, Santa Rosa, Santa Cruz, and Anacapa are the westernmost extension of the Santa Monica Mountains, one of the transverse ranges formed from this violent rotation of enormous chunks of the Earth's crust.
Once lodged in it's new position, the Transverse Range block began to be squeezed from north to south by the continuing movements of the Pacific Plate along the San Andreas fault. This squeezing has resulted in the uplift of the mountain ranges in the Transverse Range block, and for those parts of the block located underwater, that means the creation of marine terraces in the northern Channel Islands. As the block is squeezed, the islands are pushed higher above sea level. The ocean then erodes the coastline into vertical cliffs that form a step-like structure around the coast. Such terraces can be seen at many locations around the northern Channel Islands, and at places along the mainland coast where the uplift continues.
Today's photo was taken from above one of the Torrey pine groves on Santa Rosa Island. The coast of the island curves around Bechers Bay, as the omnipresent fog bank attempts to roll in over Carrington Point.
This photo was taken with a Canon EF 17-40 mm f/4L USM lens zoomed to 32 mm on a Canon EOS 5D Mk III. The exposure was set to 1/125 sec at f/16 and ISO 400.
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