Beachcombing: Southern California's geologic history, as told by the sand on our beaches

[petronius]

If you’ve walked on a southern California beach, you’ve made direct contact with the region’s ancient geology.

“I suppose I take it for granted,” says UCLA geography professor Tony Orme. He’s spent 40 years studying the way this coast has been shaped. Over millennia, sediment on beaches came down to the coast through mountain watersheds, and eroded off of coastal cliffs.

The sand on beaches between Point Dume and Redondo Beach comes in part from the San Gabriel Mountains: silvery mica, milky quartz, whitish-gray granite with flecks.

“Sediment that’s derived from granite type watersheds is generally comprised of a lot of quartz,” says Orme. “It tends to be light in color.”

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http://www.scpr.org/news/2013/07/15/38176/southern-california-s-geologic-history-as-told-by/

A short piece, but interesting: I've never really thought about sand color and texture with regard to its geologic history and watershed, and how much sand varies along the coast. Have to start paying attention at my regular beaches...

[pinto]

1. +1. Neat article & observations.

Thanks for the snag.

[JayhawkSD]

2. Many beaches have been "replenished" with foreign sand

California has restored a great many of its beaches by trucking and/or shipping in sand. Sometimes it is dumped directly onto the beach, other times offshore and allowed to wash onto the beach. Often the sand is brought from hundreds of miles away from the beach on which it is placed. That means it may not be representative of mineral that washed down from local watershed.