Jeremy McCreary
Bought it anyway
- Region
- USA
- City
- Carlsbad, CA
You're not the only one. Most of the cobble beaches here are protected from rock rustling, but there's a steady migration of these multicolored cobbles to local gardens. Including ours.
These "Poway cobbles" are found on beaches from northern Mexico to SoCal's Channel Islands. Turns out, they aren't just pretty rocks. They played a pivotal role in the history of modern geology.
The theory of plate tectonics got a firm footing first in the oceans in the late 1960s, because that's where compelling evidence was first discovered. Had to operate on the continents as well, but the first unequivocal evidence of that had to wait for Tanya Atwater, a young grad student at the Scripps Oceanographic Institution in nearby La Jolla.
Atwater traced all these Poway cobbles back to a single source — an eroded volcanic field in north central Mexico, 150-250 mi from their present locations. Then she used their distribution in SoCal to prove that the passing Pacific plate had sheared off and captured a good-sized slice of the SW margin of the North American continent.
That would be the slice I live and ride on now.
She presented the paper to a room full of the biggest big wigs in geology at a 1970 conference, got a standing ovation, became an instant superstar, and changed continental geology forever. And Tanya Atwater was just getting started.
Pretty cool for a bunch of beach rocks, huh?
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