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Smithsonian National Museum of Natural History


Meta Conglomerate
Photo by Penland. Click to zoom.
Catalog Number NMNH 116655-6
Locality California, United States

From the exhibit

Two Way Street at the Continent’s Edge

California grew when dinosaurs roamed the Earth. How? The forces that buried rocks in an ancient subduction zone returned them to the surface at the continent’s edge.

  • What went down? A slab of oceanic lithosphere, topped with sea-floor and trench sediments.
  • What came up? Some of these same rocks, now metamorphosed at high pressures and relatively low temperatures.

San Francisco’s Golden Gate Bridge is rooted in rock formed during subduction.


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