As the earth started warming up the ice started to melt. The last ice age left traces that it was there. It left GLACIERS!!! Sheets of ice covered valleys and rivers. Ice spread to different parts of the world. Scientists called it the ice age. It kept melting, then froze again. This went on for about a million years. About 10,000 years ago the earth started to warm up. Sheets of ice started to melt. As the ice melted it left lakes and broad valleys with a mixture of rocks and soil. The only ice left was up high in the mountains. The glaciers that you see now are what is left over from the ice age.