Tuesday, April 23, 2019

Guthrie Creek Geology Part II - Russ Fault Zone

I penetrated deeper towards ground zero of the Russ Fault, which is positioned south of Guthrie Creek and north of Cape Mendocino. Unfortunately, I reached a point along the beach where cliffs rise straight out of the surf zone--the surf was too rough to walk around this point, so I will have to come back during the summer when the sea is flat and the tide is low if I want to reach the true location of the fault. Nevertheless, the geology on display became progressively more extreme the farther south I hiked along the beach. Massive--as in hundreds of feet massive--blocks of hardened clayish stone have been thrusted high above the beach. These giant blocks of earth are likely being steeply thrusted upwards in response to their close proximity to the Cascadia Subduction Zone, Mendocino Fault Zone, and San Andreas Fault. This area usually experiences an earthquake, on the order of magnitude 4 or 5, every one to three months. Like anyone else, I enjoy a good earthquake from time to time. However, I was climbing over pieces of crust that clearly had been thrusted up out of the ground during the recent geological past. Thus, fearing that the 30 year return interval for a M6.0-M7.0 might verify that second, I believe I was probably muttering under my breath "not now, not now, not now."...definitely an eerie feeling knowing that I could be knocked up into the air any second if the Earth decided to move.

See the pictures below for some extreme examples of anticline folding and steeply angled blocks of earth, all of which dip toward the north.

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