Miocene: Rifting and rotation, volcanism, crustal upwelling and deposition in marine basins

B.2. Miocene: Rifting and rotation, volcanism, crustal upwelling and deposition in marine basins

Drawn and animated by Tanya Atwater using Photoshop and Morph.

When the Pacific Plate began scraping against North America, the Transverse Ranges block broke off and twirled around. The stretching thinned the crust, drawing lavas and lower crustal rocks up to fill the gap. The Santa Monica mountains and parts of the offshore Channel Islands are made of the lavas from these volcanoes. Conejo Mountain, near Oxnard is the throat of an old volcano. The stretching broke the continental shelf into many marine basins, very rich living places for marine life. These basins formed excellent habitats for microscopic floating plants called diatoms,.and the diatoms were food for swarms of tiny shrimp, and these, in turn, were scooped up by whales The pastey looking rocks that form many of our sea cliffs started out as a pile of microscopic skeletons from these diatoms. The organic parts of the diatoms slowly decayed to form natural gas, oil and tar. Fossil whale bones form the stones on some of our beaches.

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