Introduction
The Ohio River, PA Route 65, and a wooded site of a former state hospital marks the location of a major landslide created when a developer tried to build a shopping plaza on a hillside in Kilbuck Township in suburban Pittsburgh. This photo was taken prior to the development. Clck the image for the full map. Read the full story here. Let’s face it, in central and northern Indiana you are not very concerned with being buried in a snow avalanche or your house falling down a hill in a landslide. Many of these problems impact many other regions of the U.S., especially the western United States. However, some of these issues directly affect Indiana, such as sinkholes and subsidence, and in southern Indiana, landslides and rock falls do cause problems.
Many landslide hazards occur when property value outweighs concerns over the environment or long term geologic stability of a property or it susceptibility to natural hazards. Our history shows us that, in many cases, a developer or politician is only interested in the here and now (primarily money), and has little concern (or consequences) for a problem that will develop decades later when they are no longer involved.
For example, between 2004-2007 Wal-mart (and a developer hired by Wal-mart) attempted to build a store at a former state hospital in Pittsburgh on a steep bluff that overlooked the Ohio river. Rather than accommodating the store to the landscape, the development company blasted away the hillside (as shown in FIgure 9.15) to accommodate the Wal-mart. The end result was a massive landslide (article) that wiped out a major roadway into Pittsburgh. (Incidentally, the roadway itself also promoted the landslide, as it was built into the hillside too!) Wal-mart gave up on the site, agreeing to spend millions of dollars to return it to its former natural condition. (In 2008, Wal-mart filed suit against the developer, construction company, and explosives company.) Critics of the development warned that the store site would create landslides in the short and long-term even before construction began. (The links in this paragraph are not required readings.)
In this section we will study surficial processes, which include landslides, rock falls, flows, sinkholes, and subsidence. The lecture will more closely follow the textbook in this section, providing additional examples relevant to Indiana and your life. Additionally, I’ll emphasize several of the key factors in surficial processes. One topic I will build on outside of the textbook is caves! Since southern Indiana is blessed with numerous caves, we’ll take a look at how caves and sinkholes form. We’ll learn why these processes happen, and how humans can increase or decrease their risk to these events.