glacial deposits to fill in the topography. And second, the nature of the bedrock, called Borden siltstone, which is easily eroded by the natural forces into steep valleys and ridges. The northern part of central Brown County has glacial material from the pre-Wisconsin or older era. Limited glacial material is found along the edges of some deeper valleys of the streams that flow to the west into Monroe County.
Weed Patch Hill in the Brown County State Park is one of the highest elevations in Indiana at 1,058 feet above sea level. It is also the highest point along a serpentine land form called the Knobstone Escarpment that wiggles from northern Brown County southward to the Ohio River. The Knobstone Escarpment marks a transition from erodible shale to more resistant siltstone bedrock, which may have acted as a barrier to the glaciers along the Eastern edge of Brown County. Made up of steep-sided hills and valleys, these rocks of the Mississippian age form the eastern boundary of what is called the Norman Upland composed of bedrock known as the Borden Group. These
erosion-resistent, silica-rich siltstone rocks were once part of a vast delta system.
This year the country is preparing for a massive spring thaw and melt-off after the spate of extreme freezes. In geologic time, the active glaciations and the strength and force of running water acted together to erode and shape soil and rock beneath the landscape. Brown County’ s beautiful scenery is a result of that activity.
No other environmental factors since the extinction of the dinosaurs sixty-five million years ago can compare to the Ice Age in regards to the profound affect it had on our landscape and the natural world that lives on it. Ground water for 90 % of the state’ s population today, and nearly all the major aquifers this water comes from, are a direct result of glaciation. The melting ice sheets yielded the major rivers that formed the valleys where humans settled.
This past winter we have learned that climate can be local and personal. The extra school days missed or delayed because of the snow and ice will be keenly felt by Brown County students as they make up for lost time. People will talk about this winter for years to come. •
Inset of an Indiana Geological Survey map provided by Brian Keith, Indiana University. Henry H. Gray 2001
March / April 2014 • Our Brown County 23