Hiker killed when cliff collapses at California's Point Reyes National Seashore
View of the rocks and cliffs of the Point Reyes coastline. California (Shutterstock)

One hiker was killed and another injured when a seaside cliff collapsed at a park in California and sent giant boulders and earth plunging onto the beach below, officials have said.

A photograph taken from a sheriff's office helicopter showed the devastation following Saturday's collapse of part of the Arch Rock overlook at the Point Reyes National Seashore, about 40 miles northwest of San Francisco.

The National Park Service said the area had been closed to the public for safety reasons since Thursday when large fissures appeared at the top of Arch Rock, weakening the cliff.

In a statement, it said the land might still be unstable and that further collapse or erosion could take place.

The park service said bluffs on California's coast are inherently unstable and prone to crumbling. It warned hikers not to climb or walk on their edges and to be aware of falling rocks if walking near the base of a rock face.

(Reporting by Daniel Wallis in Denver; Editing by Bill Trott)