Scientists study the movement of sand on the ocean floor

Waves of sand, like dunes, are sweeping across the ocean floor, reports the County Times.  The sand winds up in Monterey Canyon.  And never heard from again.

The Monterey Canyon is the deepest underwater canyon in North America. Much of the sand that ends up in it washes from beaches in Santa Cruz, Capitola, Half Moon Bay and other parts of the Central Coast, said geologist Douglas Smith, an associate professor of science and environmental policy at California State University, Monterey Bay.

Smith and his colleagues have calculated that roughly 300,000 cubic meters of sand a year wash into the canyon — most of it coming from the north — never to be seen again. "That sand is gone forever in our time. It comes back to the surface in geologic time, but not in our time," he said.

To put that figure in perspective, it’s "enough to fill about 30,000 dump trucks a year," said marine geologist Gary Griggs, director of Long Marine Laboratory at the University of California, Santa Cruz. "That’s a lot of sand. That’s a dump truck full every 17 minutes."

Partly as a result, he said, the Monterey Bay shoreline erodes 6 to 12 inches a year on average.

The sand is naturally replenished from cliffs and rivers, but seawalls and dams have diminished these sources.