Monday, March 22, 2010

Dreamstones at Pescadero

images from Pescadero State Beach, CA, February 2010

There are sandy beaches at Pescadero, especially when the tide's out. But the whole southern stretch of shoreline is gravel, rock, and boulder beach. When I visited this favorite place of mine, the surf was high and the tide was in. I went down to the shore where the heavy boulders rise all the way to the cliffside. The waves come in, and the boulders rattle together like a room of bowling balls as the waves slide out.

This is how you make a dreamstone. The conditions of surf, tide, and materials have to be just right. At surf's edge, especially during high tide or in a storm, the waves make the boulders and smaller stones smash together. Chips fly off, and cracks appear. Perhaps a bit of sand gets lodged in a pit or crack, and the moving water swirls it around. This is the same way potholes get made in river and waterfall areas: a grinding stone in a pit or crack gets swirling around by the waters, gradually making a smooth crater.

Here by the shore, if the crater gets worn all the way through the rock, you get a dreamstone.

Depending on the hardness of the stone, the strength of the tides and waves, and time, you can get a smoothly polished stone, or one still rough-textured. Some more fragile stone weathers much faster, but then crumbles apart. Here at Pescadero, ophiolitic seafloor high-density rock is overlayered by much softer siltstones, sandstones, and conglomerates. It's very easy to see here, how seafloor spreading offshore made island arcs that slammed into the coastline, assembling California. The seafloor rocks make smooth and polished dreamstones, and take longer to carve; the siltstone fragments carve quickly and easily, but once you pluck them from the shoreline, they might crumble in your hand.

I didn't find very many new dreamstones this visit. Since the tide was in, the best place to find them, right at the surfline, was hidden by the hard-rushing waters. I mostly stumbled along the boulder field near the cliffs, still getting splashed with spray. After the previous night's fog and cold, the morning sunlight felt good on my face.

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