What are men compared to rocks and mountains?

 The shape of Santa Cruz Island is reminiscent of a wingless goose flying east with its tail pointing west and its fat body thinning into a gracefully curved neck topped with a bird head looking up. The island is approximately 26 miles from goose tail to beak and 6 miles wide at the fattest part of the goose’s belly, which totals around 96 square miles. This land mass was possibly once attached to the mainland way back when in the San Diego area. The Island has since “broken away” and rotated clockwise to its goose-flying-east position.  The geology of the island is, like all geology, complex. Now, I used to be a geology major at Whitman but it has been three years since then and geology can be like a foreign language sometimes, so I will try to break it down for you (and for my own sake, as well…I really need to brush up).

wikipedia.org

The Santa Cruz Island Fault trends east-west right through the middle of the island, causing the geology on the north side to be vastly different from the south side. The northern portion is comprised of “Miocene volcanic rocks overlain by the Monterey Formation” (Gordon et al. 2001). This means there are layers of marine sediments like shale and chert deposited on top of volcanic rocks that are between 23 and 5.3 million years old. They have been folded, warped, and pushed around for many millions on years since. The southern portion of the island mainly consists of schist—very old metamorphic rock—overlain by sandstone and other marine sediments and intruded by granitic plutons (magma that cooled underground into one big solid swath of rock that is then pushed up from below when faults move. A well-known example of an exposed pluton is Half-Dome in Yosemite). The granite on the Island is exposed in small chunks—every now and then you will stumble over a car-sized moss- or lichen-covered granite lump, or find a cool granite cave or waterfall.

One of my favorite geologic landmarks on the island is what we call the “Red-White Divide” (that has a nice ring to it, doesn’t it?). On the drive to Coches, the dirt road is reddish-orange—volcanic. At one point, the color of the road turns white. Now you are driving on ocean sediments, mostly shale and calcareous rocks. It is literally a line that divides the two, as if a child actually followed a color-by-number drawing (that never really happens, right?). The road exposes a perfect fault, where the two different geologic formations have been pushing against or along side each other for centuries.

The Red-White Divide

It’s been awhile since I took a Geology class. I was registered to take Geology of the Southern Appalachians at Warren Wilson this spring, but then I was offered this job…I’ll have to learn about North Carolina geology another time, or in bits and pieces as I hike around in the upcoming fall. I like being able to look out over a landscape and have an inkling of an idea of what could have formed it millions of years ago. 

Note: I need to cite my source above, but the document is up and the cabins, so I will try to edit the post later with that in it.