Periods in the earth's history when significant, extended cooling of the atmosphere and oceans took place are called Ice Ages. The earth last entered such an ice age about 2.5 million years ago, or the beginning of the Quaternary Period. Ice ages occur about every 150 million years, and last a few million. Scientists believe the Quaternary Period ice age we are in at the present time is not over yet.
Causes of the ice ages are a subject of controversy. The most widely accepted theory is that the earth and the whole solar sytem are located within one of the limbs of the Milky Way galaxy, which completes one revolution about every 300 million years. It seems that every 150 million years a slight change takes place in the galactic system, and might alter the earth's climate. In addition, earth based processes are involved causing climatic changes associated with continental drift.
Encompassing all ice ages are fluctuations known as glacial and interglacials: cold and warm periods that correspond to a cycle of about 100,000 years.
The longest of the ice ages was probably at the beginning of the Carboniferous Period, which began about 300 million years ago. But earlier, nearly 435 million years ago, another ice sheet extended from Brazil into North Africa, and on into Saudi Arabia.
Ice never "visited" Smith County, but did enter extreme northeastern Kansas. Generally, the west line of entry is about the Wamego area. Rocks of various sizes are deposited in the Wamego landscape where the leading edge of the ice left them set when the ice retreated.
This is a "glacial ice" deposited rock, it was left setting in the ditch of a rural road southwest of Tecumseh, Nebraska.
Pictured with the rock is Jim McDowell of Red Cloud, Nebraska. Jim is over 6 feet tall, so you can see the rock is nearly 10 feet high. The edge of the roadbed is nearly at Jim's feet, so the road almost had to detour around the rock. The movement of this boulder demonstrates the uncanny power of the encroaching ice.