Bedrock at 1900 feet - that's some mighty unstable soil come earthquake time if sand is involved. It would certainly be interesting to get a better picture of the underlying rock layer; this factoid would lend itself to the theory of a wide valley of soil overlaying a bedrock canyon of enormous size...
A question - will this soil "liquify" during an earthquake event? If so, St. Louis and any effected cities are in for a world of hurt.
The discovery channel ran a show about the New Madrid earthquakes a while back. They were showing spots where sand had risen to the surface in sand boils or blows. There were some pretty drastic changes to the landscpe not to mention changing the course of the Mississippi in a matter of minutes.
Last time I looked, the Mississippi "rift" was something like 17 miles deep, filled with dirt washed in from the Appalachians over the ages.
It's dangerous to live next to a 17 mile deep hole anywhere!
"A question - will this soil "liquify" during an earthquake event? If so, St. Louis and any effected cities are in for a world of hurt."
Have you ever read an account of the 1811 New Madrid earthquake? There are accounts online where they talk about sand spouts hundreds of feets high. They say Memphis will be toast (sunken toast) if they have another.