Caves form where wave erosion hollows out a cavity in a headland or sea cliff. If the opposite side of the headland is open, then continued erosion may eventually form an arch.
Images
Sea Cave, Arch and Stacks Burchfield, B. Clark; Foster, Robert; Keller, Edward; Melhorn, Wilton; Brookins, Douglas; Mintz, Leigh; Thurman, Harold.
Physical Geology.
Charles E. Merrill Publishing Co., 1982.
