The Big Bend This map shows the geometry of the plate boundary between North America and the Pacific

The Big BendThis map shows the geometry of the plate boundary between North America and the Pacific Plate. These 2 plates are grinding past each other, with about 90% of the motion represented as strike-slip displacement from the Pacific Plate heading North relative to the North American Plate.The San Andreas Fault is the southern boundary between these two plates. A large strike slip fault, the San Andreas takes up about 80% of the motion between the two plates, with the rest distributed on smaller faults throughout the two plates.Just northeast of Los Angeles, the San Andreas does something rather odd. It bends sharply to the left, before heading back to the northwest on its path towards San Francisco. This division in the fault is nicknamed the “Big Bend”, for obvious reasons as you see here.Faults can be represented as lines on a map, but in reality they are complex structures penetrating the entire crust. At the northern tip of the Big Bend, the San Andreas intersects another strike-slip fault, the Garlock Fault, that runs out into the Mojave Desert and disappears into heavily damaged rocks in Death Valley that are described as a “mélange” zone. Motion on the Garlock Fault, combined with other deformation in the Mojave Desert, has helped set the current course of the San Andreas.Scientists have worked hard to understand how these faults link together and how they link to the surrounding topography. Just south of the bend in the San Andreas you will find a number of mountain ranges including the San Gabriel Mountains and the San Bernardino mountains. Both of these ranges have shot upwards in the last few million years as the San Andreas system integrated.When faults step to the side, as we see in the Big Bend, they can create either openings filled with normal faults or mountains. In this case, the rocks riding northwards along the San Andreas basically run into a brick wall – they slam into the bend in the fault, creating compressive forces as they are forced to the side. This compression is shoving up the mountain ranges that surround the Los Angeles basin and has created faults and the Tranverse Mountain Ranges to the west as material is pushed to the side.-JBBImage source:https://commons.wikimedia.org/…/File:Sa…References:http://bit.ly/2zwua5jhttp://bit.ly/2hZEOu3http://scedc.caltech.edu/…/sec1pg27.html -- source link

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