Every time we are in Mendocino we find ourselves at Glass Beach. It's just up the road in Fort Bragg and is the most interesting State Beach Park I've been to. We happened upon it accidentally many years ago and now the kids beg to spend every waking minute of our vacation time there.
Starting in 1949 garbage was dumped into the ocean in and around the Glass Beach area. We're talking old cars, miscellaneous household items and lots and lots of glass. This went on until 1967 when it was finally realized that dumping trash into the ocean may not be a good idea. However, by then so much refuse had been dumped, it just became kind of an aquatic graveyard.
Amazingly, mother nature took over. After years and years of grinding and pounding in the waves of the rocky coast, Glass Beach was born. These rocks and millions and millions of pieces of glass sit on top of the sand. No spot is left uncovered. There is enough sea glass to fill millions of wheelbarrows and there would still be some left over.