Figure 19.8
Longshore current and longshore drift. (A) Wave swash moves up the beach at an angle, but gravity pulls the backwash straight down the slope of the beach. As a result, sand follows a zigzag path down the beach in the process of longshore drift. (B) Along the Chandeleur Islands, off the coast of Louisiana, longshore current and longshore drift result as incoming waves approach the beach at an angle. The resulting movement of sand gradually lengthens the island.(B. © Annie Griffiths/National Geographic/Getty Images)