Frozen Illinois, 1.8 Million Years Ago
From 1.8 million to 12,000 years ago, massive sheets of ice advanced across North America many times. This period is known as the Pleistocene. Glaciers originating in eastern and central Canada extended into parts of Illinois during long cold periods. They melted back during shorter warm phases of interglacial climate. The Earth was about 4.6 billion years old. Geologically speaking, the Pleistocene was just a moment ago, and a map of the continents is like today's map.