As news spread throughout Homer last week of a massive uplift on the Diamond Creek beach below Bluff Point, scientists examined the bizarre geological event to figure out what caused the tidelands to rise up 20 feet. Their conclusion?

Think a huge landslide off Bluff Point cliff that hit the bench below like a giant piledriver. The force of tons of rock and dirt hitting the land in turn probably caused a zone of weakness from an ancient landslide to give way, said Bretwood Higman, a Seldovia geologist. That caused land at least 100,000-square-feet in area to rotate and slump, with the sea edge tilting up and the inland edge falling down.

Last Saturday, Higman and Dick Reger, a retired geologist with the Alaska Division of Geological and Geophysical Surveys, visited the Diamond Creek uplift. They weren't alone as dozens of beachgoers made the trek down the Diamond Creek beach and about 1.3 miles east of the creek toward the uplift. The uplift appeared to have happened sometime late July 2 or early July 3.

Before visiting the uplift, Higman had speculated that if there had been a rotational slump, there should be a corresponding subsidence inland of the uplift.

Last Saturday, he found that.

"It's very dramatic. There are big fissures that jutted up. At one spot was a 10-foot wall poking up," he said.

Higman also noticed a fresh scar on Bluff Point where a chunk fell away.

"It more peeled out and slid down. It almost looks like it dropped straight down," he said. "It looks like that shifted out, pushed down, then triggered the whole shelf shifting down, and that's what drove the beach up," Higman added.

Visitors described clay walls 10 to 15-feet high extending along the inland side of the slump. Photos Bluff Point residents Ron and Marilyn Hess took show the subsidence taller than an adult man.

"As soon as I hit the bluff face it was clear the whole shelf had dropped," Higman said. "It's not subtle at all. It's very dramatic."

The whole beach appears to have been moved, he said. Boulders on the beach had resettled, leaving behind depressions in the cobble beach. From the ground it's hard to fathom, and even looking down from Bluff Road -- a narrow, rough road at the top -- it's hard to take in the spread of the slump and uplift. Even at high tide, the uplift still poked above the waves.

The cliff remains unstable, with small rocks and slides continuing. The top of the 800-foot cliff -- the same cliff where Wanda Darling fell to her death in 1997 -- overhangs the edge and is dangerous to be near.

In geologic time, an uplift like this is not all that rare, although one happening so near a populated town is unusual. The size and scale of it makes it a geologist's treasure, though.

"It would be a really good master's level project," Higman said. "This is big. It's plenty big. You could depict what's happening very clearly."

Rod Combellick, a DGGS geologist in Fairbanks, said the state does not plan to study the uplift. If the city or borough wanted to assess any geologic hazards -- the Bluff Point landslide crosses city limits -- he said officials could hire a consultant to do a study.

"It's good to have a reminder the earth is alive," Higman said "On the grand scheme of things, this is very normal. Now that we have a lot of information about this uplift event, it's not mysterious."

Michael Armstrong can be reached at michael.armstrong.@homernews.com.