Ocean waves have eroded the perimeter of the island, creating steep sea cliffs towering hundreds of feet in height and exposing the volcanic origins of air pockets, lava tubes, and sea caves. At the east end of Anacapa a natural bridge has formed in the ocean. Forty-foot high Arch Rock is a trademark of Anacapa and Channel Islands National Park.
Waves and currents aided by weathering agents undermine rock cliffs, cutting out coves, causing rockfalls and landslides, grinding up rock debris to make sand for beaches, and transporting sand along the shore.
Here at Cape Breton Island, Nova Scotia, wave action has eroded the headland leaving these more resistant rocks still exposed. Although not classical sea stacks due to their slanted structure, the process is the same.
Pacific waves pound a resistant headland of rocks of the Western Franciscan Complex and break on a small beach of sand supplied by the wave action, longshore currents, and the stream bridged by California Route 1.