Palisades Landslide Shuts PCH : Geology: Rain-soaked bluff collapses, dumping 30-foot-deep pile of debris onto highway. Traffic is expected to be disrupted until tonight.

A massive landslide in geologically unstable Pacific Palisades buried a section of Pacific Coast Highway under up to 30 feet of rain-soaked earth, rock and debris Monday afternoon, and officials said it probably will take until tonight to reopen the heavily traveled thoroughfare.

Despite the suddenness of the bluff’s collapse, no one was believed trapped beneath the slide. Nonetheless, high-tech sonar and infrared searching equipment was brought in to probe the fallen earth.

Wilton Miller, an MTA bus driver, said he had been heading north on Pacific Coast Highway in his empty bus about 2:30 p.m. when the traffic light at Chautauqua Boulevard turned red. Just as the bus started to move again, “a cloud of dust, a big tree, came tumbling down” ahead, Miller said. “I thought it was an earthquake at first.”

The bus driver said that as he watched in awe, the entire hillside in front of him collapsed, tumbling across the highway with an immense roar, scattering four-ton concrete barriers erected earlier in a futile effort to stop such landslides before they reached the highway.

Several large eucalyptus trees and some fencing that had once topped the bluff crashed down with the sliding earth, ripping away power lines.

“It sounded like an auto accident, like an explosion,” said Daniel Powell, a building contractor who was working on an apartment building at Chautauqua and PCH.

“If I hadn’t stopped for that light at Chautauqua, I would have been under there,” Miller said later.

Miller and another witness, who was not immediately identified, said they thought the coast highway was clear of vehicles and pedestrians when the slide occurred. However, a third witness, who drove off before officials could question him, reportedly said he might have seen a car in the slide’s path.

As a precaution, fire officials brought in some of their most sophisticated search equipment.

A sonar unit probed the earth with sound waves, looking for shapes that might be a car or a motor vehicle. Infrared equipment, penetrating the soil like a giant X-ray machine, searched for signs of warmth that could come from a human body.

The officials found nothing, but they vowed to continue their search until they were certain no one was buried in the slide.

Robert Schuster, a civil engineer with the U.S. Coast and Geodetic Survey offices in Denver, said the slide was the product of the unusual geology in the area and this winter’s unusually heavy rains, which weakened the coastal bluffs while adding to their weight.

“You have steep slopes there, (composed of) rocks so soft they are almost soils, especially susceptible to water,” he said. “You get a hell of a lot of rain, it gets unstable and the whole thing comes down.”

It had not rained in the area since Thursday, but Schuster said landslides frequently occur days, or even weeks, after the rains that cause them.

“It happens all the time there,” he said. “It sometimes takes quite a while for the water to seep into the soil and weaken it. There’s a lag time.”

A 300-foot section of the Palisades gave way in Monday’s slide, leaving a ragged scar across the bluffs that tower about 80 feet above the highway. The bluffs are topped with expensive homes, perched on real estate that has become increasingly precious.