Molly Tominack's home is built on soil that she thinks would be better employed as an artist's material or a children's toy than as the base under her house's foundation.

On a recent afternoon, Tominack picked up a chunk of the clay mixture that lies inches below the surface of her yard in North Indian Head Estates in western Charles County and tossed the clay into the water of her bird feeder. Wet, the material became slimy and malleable.

"It's amazing!" Tominack exclaimed, pushing the clay around with her fingers. "It goes absolutely plastic, like modeling clay."

Of course, no one would build a home on modeling clay, and Tominack is wondering if her house ever belonged on the land where it sits. The soils that geologists call highly "plastic" in Tominack's neighborhood apparently have been shifting in the last year or so, leaving dramatic scars on at least a dozen houses in the area -- cracked foundations, broken bricks, dislocated cement blocks and ruined patios. Pieces of several foundations actually have shifted to the side like tectonic plates moving in an earthquake.

Charles County commissioners said this week that they will consider whether to require developers to conduct geotechnical surveys and modify their building plans to take such local ground conditions into account. Some counties already have such laws.

Repairing the damage to houses in Tominack's neighborhood will cost thousands of dollars, and it's not just residents who express dismay. County officials are concerned that the problem could spread, since similar plastic soils lie in other areas of the county. Some recent development sites -- and others still in the planning process -- may be at risk, residents suggest.

Commissioners heard this week from consultants hired in January to find out what was suddenly causing damage to Tominack's 35-year-old house and others on Dakota Court and Dakota Street. An engineering firm concluded that the various clays in the soil -- combined with recent weather conditions -- were the culprit.

So-called expansive and highly plastic soils expand and contract as moisture levels fluctuate, the engineers explained.

"The expansive soils in the ground in this area -- when they get wet they swell, and as they dry they shrink," said Allen May, one of the consulting engineers. "This can cause heaving and settling and thereby cause cracks in a house's foundation."

Charles County's wet weather in the first half of 1998 followed by near-drought conditions later in the year set the stage for dramatic shifts in the clay mixture.

The consultants recommended that the county require geotechnical testing for new development. Board of Commissioners President Murray D. Levy (D-At Large) said the county would consider possible regulations.

Other jurisdictions, such as Prince George's County to the north and Fairfax County across the Potomac, already have laws dealing with unstable soils.

Prince George's has mapped out areas of the county where the soil includes expansive clay. When developers want to build in these areas, they are required to perform a geotechnical study.

"We want to ensure that there won't be a loss of property due to unsafe lands," said Nick Motta, chief of the natural resources division of the Prince George's County Planning Department.

"The developers can engineer their way past a lot of the problems, but there's a point when it becomes un-economical."

Charles County has reason to worry about several development sites, said Elmer Biles, an Indian Head resident and environmental activist. Biles pointed to a landslide susceptibility map showing several areas of Marlboro clay in the county. Marlboro clay is an expansive soil known to cause landslides, and it is one of several clays in the ground at Dakota Court. The map shows similar soils where new houses are being built at Strawberry Hills and Montrose Farms, Biles said, as well as the proposed developments at Falcon Ridge and Hunters Brooke.

Just a few streets from Dakota Court lies the South Hampton development, where new houses still are being built. Several two- and three-year-old houses there are showing cracked foundations, driveways and porches -- damage that may be caused by unstable soils.

The county plans to determine the cost of fixing the foundations of the Dakota Court houses. Some homeowners may have to extend their foundations' footings into the ground. Engineers also suggested a simpler remedy -- removing vegetation from around the house. Trees and other plantings, May said, can suck water out of the ground and thus alter the soil's moisture level.

Residents said they are hoping for state or federal disaster relief to help pay for repairs, an idea commissioners said they will examine. Many of the homeowners are retirees living on a fixed income.

Juliane Prebble, 67, who survives on her monthly $667 Social Security check, seems overwhelmed by the fault lines spreading along her walls. She blockades her front door at night because the walls are so warped that the lock does not work properly.

"I don't know what to do," Prebble said. "I can't even afford payments on a low interest loan. My kids tell me to sell the house, but if I had to rent an apartment I wouldn't be eating. It's a sad thing."