Thanks to the Ice Age
~ by Julia Pearson
At the time of this writing ice and snow is melting into rivulets from the rooftop gutters and is rushing down sidewalks and roads. The polar vortex that slammed into our nighttime weather left inches of ice on everything. Snow was shoveled into white mounds that stubbornly clung to the ground, despite temperatures that bounced intermittently above freezing.
It’ s been a winter of bitter, frightening cold. The kind of cold that shuns the seasonal Currier and Ives scenes of sleigh rides, snow men, and fields of animal tracks and the imprint of children’ s snow angels. Wildlife settled down into secret places. State and local leaders urged everyone off the roads. Skin and lungs both were damaged by the air that was almost metallic in its severe power to hurt.
Swapping stories of past episodes of mad temperature drops became part of the community conversation.
Some Hoosiers recalled signs placed on the roadside by the highway department around 1937 that pictured an outline of the state and marking“ Glacial Boundary.”
Those signs no longer exist, but they marked the evidence of nature’ s impact on our landscape.
Indiana’ s geologic history is reconstructed through core sediment analysis, geophysics, and stratigraphy. The first ice sheet entered Indiana sometime before 700,000 years ago directly from what is now Michigan. In general, geologists divide the Ice Age into three great stages, and the glacial deposits they left behind: the Wisconsin Stage, which began about 50,000 years ago and covered nearly two-thirds of Indiana; the Illinoian Stage, which took place from 300,000 to 140,000 years ago; and the pre-Illinoian Stage, which is much less clearly understood. Based on the information provided by the Indiana Geological Survey it is clear that Brown County’ s magnificent hills exist because the multiple periods of glaciations in Indiana’ s geological history stopped at the northern edge of the county.
Brian Keith, Senior Scientist with the Indiana Geological Survey at Indiana University says the rugged topography of Brown County today is related to two factors. First, there were no extensive
22 Our Brown County • March / April 2014