At temperatures of around 2,000°C, sand turns into glass. Sometimes, in the event of a lightning strike (or, even rarer, a meteor hit) the resulting heat can fuse the grains together and produce glass entirely naturally. This is not what happened at California’s Glass Beach.
Enjoy the Wonder of Ft. Bragg's Glass Beach While You Still Can
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Glass Beach – Fort Bragg, California - Atlas Obscura
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