Devil’s Punchbowl is a sinkhole formed by a collapsed sea cave over 70 feet (21 m) deep and 100 feet (30 m) in diameter in Russian Gulch State Park, about 8 miles (13 km) south of Fort Bragg and 1.6 miles (2.6 km) north-northwest of Mendocino, California. Devil’s Punchbowl is connected to the ocean by a tunnel and at high tide seawater fills the bottom of the pit.

The littoral zone is the nearshore part of a sea, lake, or river. In coastal environments, the littoral zone extends from the high watermark, which is rarely inundated, to depths that are always submerged. The littoral zone always includes the intertidal zone, and the terms are often used interchangeably. A collapsed sea cave is also known as a littoral sinkhole, and the driving force in the development of a littoral sinkhole is wave action that causes erosion. Erosion is ongoing anywhere that waves batter rocky coasts, but rock is removed at a greater rate where sea cliffs contain zones of weakness. Adding to the hydraulic power of the waves is the abrasive force of suspended sand and pebbles, and the oscillating motion of cobbles and boulders. Most sea cave walls are irregular, reflecting an erosional process where the rock is fractured piece by piece. However, some caves have walls that are rounded and smoothed, typically floored with cobbles, and result from the swirling motion of these cobbles in the surf zone. Sea caves have been documented in all four states on the Pacific coast. The largest concentration of sea caves is found in the Channel Islands of southern California, where over 9 miles (15 km) have been surveyed in 380 caves, but large caves are also known from the central California coast.

Russian Gulch State Park is part of the Russian Gulch Marine Conservation Area. One goal of the conservation area is the restoration of kelp forests. Kelp forests are a vital feature of California’s coastal seascape and form the foundation of a rich community of fish, invertebrates, and marine mammals. A small marine protected area has existed at Russian Gulch since 1970 as part of the state park, but in 1999 the Marine Life Protection Act directed the state to redesign its existing marine protected areas into a more comprehensive network. The new Russian Gulch State Marine Conservation Area was established in 2012, along with 19 other north coast marine protected areas. Read more here and here. Explore more of Devil’s Punchbowl here: