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FORT WASHINGTON, Md. (WUSA9) -- The dense soil layer that may have caused the earth to slip in Ft. Washington was deposited around 55 million years ago, when much of the land where we sit was a shallow sea.

But should you be worried about Marlboro Clay?

On a geologist's one to four ranking of soils most likely to cause landslides, Marlboro clay is a four.

Some building codes require you to excavate and replace it if it's on the surface.

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