In Seattle, there's a lot of potentially dangerous places where the soil could give way any moment. This is especially true in neighborhoods with good views.
The City of Seattle publishes a landslide map that makes this abundantly clear. On the map, landslide-prone areas are marked in red. And, boy, is there a lot of red! http://stream.publicbroadcasting.net/production/mp3/kplu/local-kplu-943288.mp3
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The map also has numerous black dots showing where a landslide occurred. The graphic is published as part of a larger study on landslides within the city limits.
Seattle-area Real Estate Appraiser Richard Hagar says for those looking to buy a house near a creek or on a bluff - or beneath a bluff, for that matter - it pays to know as much as you can about the soil it's on, next to, or even below (think house at the bottom of a clay bluff). Otherwise, you may end up with a lot of mud in your mud room!