California, San Mateo County, Daly City
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Here at Thornton Beach, the ground is not as solid as it seems. The ground itself is made up of a semi-consolidate sedimentary rock from here to Mussel Rock. It doesn't hold together well, which makes the coastline very unstable.
Constant pounding of the surf along Daly City coast undercuts the cliffs. Rain scours and penetrates the soil loosening the rock structure. Gravity pulls the weakened slopes down in slumps and slides. If that weren't enough, the San Andreas Fault runs 1/4 mile from this spot. Ground shaking from earthquakes causes landslides too. Geologists believe the shelf below you, between this elevation and the shore, is a mighty rotational slump triggered by the 1906 earthquake.
This Daly City beach was once accessible by road. In 1982 heavy rains and unusually large tidal action undercut the cliffs from Thornton Beach south to Mussel Rock, causing a massive landslide. Concern over safety keeps the 56-acre property and beach inaccessible.
(Natural Features) Includes location, directions, 3 photos, GPS coordinates, map.
Here at Thornton Beach, the ground is not as solid as it seems. The ground itself is made up of a semi-consolidate sedimentary rock from here to Mussel Rock. It doesn't hold together well, which makes the coastline very unstable.Constant pounding of the surf along Daly City coast undercuts the cliffs. Rain scours and penetrates the soil loosening the rock structure. Gravity pulls the weakened slopes down in slumps and slides. If that weren't enough, the San Andreas Fault runs 1/4 mile from this spot. Ground shaking from earthquakes causes landslides too. Geologists believe the shelf below you, between this elevation and the shore, is a mighty rotational slump triggered by the 1906 earthquake.
This Daly City beach was once accessible by road. In 1982 heavy rains and unusually large tidal action undercut the cliffs from Thornton Beach south to Mussel Rock, causing a massive landslide. Concern over safety keeps the 56-acre property and beach inaccessible.
(Natural Features) Includes location, directions, 3 photos, GPS coordinates, map.