From Colossal Art & Design:
"... In 1967 the North Coast Water Quality Board closed the area completely and initiated a series of cleanups to slowly reverse decades of pollution and environmental damage. But there was one thing too costly (or perhaps impossible) to tackle: the millions of tiny glass shards churning in the surf. Over time the unrelenting ocean waves have, in a sense, cleansed the beach, turning the sand into a sparkling, multicolored bed of smooth glass stones now known as Glass Beach. ..."
More at Wikipedia: [Link]
And even more at Fort Bragg.com: [Link]
There is a very nice collection of macrophotography at the site.