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Stop 8, Active Folding in the Central Valley

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Stop 8 is at 38°32.857´N, 121°50.435´W across from a school east of Winters. (more below)
A gentle sign of tectonic energy
Photo (c) 2006 Andrew Alden, licensed to About.com (fair use policy)
Out in the flat Central Valley there are subtle signs like this of tectonic activity. The same thrust faulting that has upturned the rocks and raised the Coast Range extends into the western edge of the valley as well. The thrusts reflect a degree of compression across the San Andreas fault system in addition to the lateral, strike-slip motion that is carrying coastal California northward. The 1985 Coalinga earthquake, in the southern part of the Central Valley, was caused by just this sort of hidden thrusting.

The Central Valley is thought to lie so low because a slab of heavy oceanic lithosphere—the Great Valley ophiolite—is attached to the crust there. A recent hypothesis holds that splitting off (delamination) of that heavy layer is causing the recent, rapid uplift of the Sierra Nevada today.

Day 1, Coast Range: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

Day 2, Sierra Nevada: 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18

Day 3, Sierra Nevada: 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28

Day 4, Coast Range: 29 | 30 | 31 | 32 | 33

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