What is a Sinkhole?

Sinkholes you might have heard pop up or sink down which is visually the case in surprising places, but they're predictable if you are a geologist and are aware of the soil and rocks underneath a given terrain. In Pennsylvania, for instance, where I grew up there are sinkholes that are visible because of the underlying rock in the Appalachian Mountains. Limestone, you see, which is prevalent in the entire range of the Appalachian Mountains is subject to erosion because the rock is so soft--it easily dissolves into solution which means water and is carried away and in the process it carries away the floor under your feet. It literally erodes the support under your feet which is what happens when a sinkhole appears. Where I lived in Lock Haven, Pennsylvania which has limestone caves all over the place we had an instance of limestone sinkholes appearing in our driveway and my Dad--who as a matter of fact was a geologist--explained the logic of the sinkhole and we found ourselves needing a new driveway because of what he understood the problem to be. Limestone rock is used as filler for road projects and to flatten out road and driveway surfaces for paving. It turns out that limestone filler can become degraded if water infiltrates and is able to take away the calcium which provides a lot of the bulk of the filler. Caves in the Appalachian Mountains are carved from limestone rock so you can see how limestone is subject to erosion. If you're a fan of Hogan's Heroes you might remember that they were constantly digging tunnels. It appeared as if someone was digging a tunnel under our house since the depressions in our yard appeared in a line which was consistent with a tunnel...so if you have sinkholes in your yard maybe someone is digging a tunnel into your basement. In my case our basement was partially a dirt floor. It was a great joke to consider that our neighbor was digging into our basement. CJ Snare of Firehouse was my next, next door neighbor when he moved into our neighborhood when I was about nine years old. Maybe he was digging through to find a place to play his music. Maybe my German neighbors were digging through to spy on my post-war reaction to the world of sixties politics. The principal--by profession--on the East side of my house was a suspicious character by his impeccably upright roots. His son probably wasn't digging into my house because the direction of the path was wrong. I considered the possible source of the possible tunnel into my basement and decided it was either the Germans on my West which means it was spy activity or CJ Snare which means it was most likely a rock n roll stage in my basement he was digging for. Rock n rollers are serious so ask CJ about it. Maybe he found a German spy tunnel when he was digging and he took it over. Maybe there was a fight for control of the tunnel underneath my house. Could there be bodies there still? Let's investigate!