Geology Term of the Day: Terrane

Terrane, not Terrain. More specifically a tectonostratigraphic terrane

In geology terrane is a block of the Earth’s crust from one tectonic plate that get attaches (accretes) to another plate. A piece of the earth’s crust that differs from the surrounding material, and is separated from it by faults.

Where are they found?

All over California, dude. All over.

Example? Part of Ben Lomond Mountain in California is part of the Salinian Block that is found parts of Santa Cruz County, the Monterrey Peninsula, Bodega Head, Point Reyes and the Farallon Islands. The source of these rocks? The Sierra Nevada Mountains… at least 150 miles to the southeast of the Bodega Bay. How did they get there? After being sliced off the Sierra Nevadas they moved along the San Andreas Fault guided in part by the Big Pine and Nacimiento Faults.

Farallon Islands photo by NOAA

Why does this matter? Ben Lomond Mountain is an AVA which is located on this geological intrusion. Kinda makes the area different from the surrounding terrain, doesn’t it?

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