Towns and cities across the U.S. have been dealing this spring with fast-moving natural disasters, from tornadoes to flash floods.

In northern New York and Vermont, the disaster has developed slowly. Weeks of torrential rains have glutted Lake Champlain, flooding hundreds of miles of coastline.

Now, in the mountain village of Keene Valley, N.Y., all that water has triggered a massive landslide that is slowly destroying a neighborhood.

'Largest Landslide In State's History'

Town Supervisor Bill Ferebee walks along a gravel road, stepping over big fissures.

"This all, this area has just dropped," he says.

He's here to inspect one of the dozen houses perched on Little Porter Mountain. It looks like someone grabbed the entire structure and gave it a fierce twist.

"You can see here how the house has lifted," he says. "This has lifted in just the last three days. So the house is tipping forward."

The house is owned by Pam Machhold, who stands in her driveway, arms folded. A few weeks ago, she says, the property was appraised at more than $600,000.

"There's nothing we can do," she says. "It's condemned. The house has got to be taken apart because it'll collapse upon itself. The house is gone and the property is absolutely useless."

Nearby, a stream surges with water. New York's Adirondack Mountains saw heavy snow last winter. The spring melt combined with record-setting rain has literally broken loose the entire flank of the mountain.

New York state geologist Andrew Kozlowski says hundreds of thousands of tons of rock and earth have been destabilized.

"The area that's moving, that's impacted, is 82 acres," he says. "Eighty-two acres of land mass on the side of the mountain is physically moving. It's the largest landslide in the state's history."

More homes and businesses sit at the bottom of the slide. It's oozing slowly, Kozlowski says, no faster than three feet per day. But it's so big that scientists have been arriving from all over the country to study it.

"We still have very little in terms of subsurface information to understand the depth and the actual extent in the subsurface of how wide this event is," Kozlowski says.

Gathering good data has been tricky, in part because the terrain is incredibly treacherous, with trees toppling and boulders kicking loose.

"It definitely gets your attention when you hear the trunks cracking as a mass," Kozlowski says. "The boulders you hear a thumping, tumbling sound and you sort of look up and catch a glimpse and you hear them hitting tree trunks as they're moving downslope. And so you just try to get between a tree and where you think they're coming."

A Broken Heart

Just down the road, a truck is pulling away from another threatened home, salvaging furniture owned by Charity Marlatt. Her house is perched at the very top of the slide, its foundation half-exposed.

Marlatt says she was in the garden and first realized that something big was happening when she noticed something small.

"My planting table was tilting, and then we really started to look and at that point it was just a small crack in the lawn," she says.

Marlatt was forced to evacuate and now she and her husband are trying to find an engineer who can lift their home and pull it back from the brink.

But the slide keeps growing and Marlatt says the ground is still so saturated that they have to wait.

"If I weren't so emotionally involved, if my heart weren't so broken right now, this would be a fascinating situation," she says. "Because I've learned more about geology than I would probably care to."

Scientists say they haven't got a clue when Little Porter Mountain will stop moving or how much of the neighborhood will be swept away before this slow-motion disaster is over.