<human>:  When did the Ice Age start?
<bot>: The last Ice Age started about 20,000 years ago and ended about 10,000 years ago. The last Ice Age was caused by a decrease in the amount of sunlight reaching the Earth, which caused the Earth's temperature to drop. This caused the sea level to drop, which exposed land that had been covered by the sea. This exposed land was then covered by glaciers, which caused the ice to grow.