Pittsburgh is prone to landslides. We sit on a 40' bed of clay and shale and when it becomes supersaturated, as it has this year, it becomes very slippy.
Add to that our topography of steep valleys between high ridges, and builders who bulldoze the tops of these ridges in order to have enough flat space for the houses they build and you have an invitation to earth movement.

This house used to perch up above the neighborhood of Hays, in the city's south side. It stopped short of it's goal of Hays proper, but is no longer habitable.

Most Pittsburgh landslides are "back yard slides" where the backyard of a suburban family slides down to the street below. Baldwin is particularly susceptible to back yard slides. We had one the first year we moved here; lost 3' off our driveway as the slope below it began moving. I remember walking around the slope in the rain, weeping at each new crack I spotted. Luckily there is quite a distance between our yard and the street below and our lump stopped moving well short of its goal. We planted trees with deep roots -- poplars, sycamore, and then black walnut and buckeye. After 30 years, our slope is now stable and we have a lovely woods to look out on.

There is a second, darker side to the clay we build on. When there is a draught, it contracts and foundations move and crack. The slab we poured for a carport is now 4" below it's original level.

This is information that newcomers to the area should know about when they purchase a home with a view!