853. Beach Sand Cycles

MOSS: One of the things that make Asilomar's dunes unique is the sand. NARRATOR: State Park Senior Environmental Scientist Tom Moss. MOSS: The sand is derived entirely from the breakdown of the offshore rocks and the decomposition of the shoreline. The offshore rocks are granitic and the material that forms from that is- very clean, it's almost pure quartz and feldspar. It's very, very clean sand. NARRATOR: When you’re on the beach, you might notice a squeaking sound when you rub your feet across the white sand. This is because the sand is made from pure rock, without clay or other organic material. As Tom Moss says, this sand is, MOSS: …squeaky clean… NARRATOR: You may not see it, but this beach sand is hiding an army. Marine organisms, like worms, crabs and tiny invertebrates populate the first six to eight inches below the sand’s surface. Some of these organisms are so small; they can live between the grains of sand! The waves provide a free lunch. When seawater washes over the sand, it percolates down, carrying plankton and dissolved oxygen to nourish the creatures below. The beach changes shape throughout the year. Waves and wind shape the beach with the seasons. Huge winter waves pull beach sand into the ocean to form offshore sandbars. You may see waves breaking far from the shoreline. Spring brings smaller waves that deposit sand back on shore. Late spring winds blow the sand inland to the first series of dune ridges, or “foredunes”. There, it’s caught by plants, and the dunes grow taller. Park staff re-vegetate the foredunes as needed to keep the balance between erosion and build up of sand.