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Geologic Trips, San
Francisco Cliff House The Cliff House (right)
is built on thick
sandstone beds of the San Bruno Mountain terrane, shown in this photo. The sand in these
rocks was derived from weathering of granitic rocks in the ancestral Sierra Nevada. The sand was carried from the ancestral Sierra
Nevada by ancient rivers and then deposited in a deep oceanic trough that had formed along the Franciscan subduction zone during late Cretaceous time. These sandstones appear somewhat
similar to the Alcatraz
terrane, but the Alcatraz sandstones are older and were formed during an earlier
stage of subduction Exterior Website Golden Gate NP Conservancy: _____ |