From SOTT:

San Francisco — A new explanation for colliding faults could help explain mysterious fault lines that have mystified geologists for decades. The new explanation could explain everything from the quake-prone faults of Southern California to dynamic crust beneath the snow-capped peak of K2 in the Himalayas.

The theory is deceptively simple: When two faults collide, instead of one breaking past another, they may just merge, like a zipper zipping up, said John Platt, a geologist at the University of Southern California in Los Angeles, here at the annual meeting of the American Geophysical Union. [Photo Journal: The Gorgeous San Andreas Fault]

“It may solve some long-standing and intractable problems concerning the timing and displacement on faults,” Platt said in the presentation.

Strange rocks

Platt and his colleague Cees Passchier, a technophysicist at the University of Mainz in Germany, were looking at a strange rock formation called Cap de Creus in Spain. To a geologist’s eyes, the rocks make no sense, with rocks on one side of the fault showing signs of shear in one direction and those on the other side having the opposite shear orientation. Normally, the direction of motion revealed in the rocks should be the same on either side of the fault. (At Cap de Creus, the textural lines in the rocks make a “V” shape around the fault, while normally that texture would look more like diagonal lines that cross the fault.)

Passchier “showed it to me in the field; it just blew my mind. I thought ‘There’s just no…

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