Bowling Ball Beach, Schooner Gulch State Park, California, USA.

Bowling Ball Beach, Schooner Gulch State Park, south of Point Arena, Mendocino County, California, USA. Pacific Ocean waves have weathered coastal bluffs (steeply tilted beds of Miocene Galloway Formation, Cenozoic Era mudstone) to expose spherical sandstone concretions resting on bowling lanes. Concretions form because minerals of like composition tend to precipitate around a common center.