This sea arch at Goat Rock Beach south of Jenner, California, is unusual in that it sits offshore. The usual method of forming a sea arch is that a headland focuses incoming waves around its point and onto its flanks. The waves erode sea caves into the headland that eventually meet in the middle. Soon enough, maybe in a few centuries at most, the sea arch collapses and we have a sea stack or a tombolo
, like the one just north of this spot. Other natural arches
form inland by much gentler means.