Eighteen thousand years ago, a huge ice sheet thousands of feet thick covered present day Canada and the northern United States. This is an account of the recolonisation and transformation of this Arctic landscape as the ice melted and receded over the next milennia. The author shows how the soil and vegetation developed, followed by an increase in the diversity of animal life, right up to the colonization of the land by early human settlers. In addition, she also reveals how scientists can reconstruct the past from fossil and geological evidence.