Landslide Expert: Geology, Wet Weather Make Coastside Cliffs Hazardous

SAN FRANCISCO (KPIX) -- A combination of factors led to the disastrous cliff collapse that buried two women, killing one of them, on Friday afternoon at San Francisco's Fort Funston.

Not least among them is the recent spate of wet winter storms.

"When we have these big rains they saturate the ground and that weakens the soil and rocks and clearly what happened today was directly in response to this rainfall," Dr. Roland Burgmann, a landslide expert at UC Berkeley, told KPIX.

Then there's the substance of the coastside cliffs. Signs warning of unstable cliffs are numerous at Fort Funston and regular visitors are well-aware of the impermanent nature of the stunning coastline.

"(All of the cliffs) up and down the coast from Pacifica to Daly City is made up of the Merced (formation) foundation, the cliffs are made up of this young rock, and it's very susceptible to failure and landsliding, so this is a known problem," Dr. Burgmann explained.

Dr. Burgmann says limiting access to the beach while the cliffs stabilize would be wise.

"These failures, they don't happen that often, but they do happen on a regular basis. Given that we just had this huge event, it makes sense to me personally to keep the area off-limits for a while and certainly not let people walk up to the cliffside."