ABSTRACT
BACKGROUND: THE PLEISTOCENE IN NORTH AMERICA By the onset of the Quaternary Period the continents were close to their present positions, although the mid-Atlantic ridge was continuously spreading. At this time, 2.5 million years ago (Bowen, 1999), there was a dramatic deterioration in the climate which over much of North America and northern Europe and Asia remained cold to glacial during the whole of the Quaternary, with temperate to warm intervals of short duration. This is the period of Earth’s history known as the ‘Great Ice Age’, when the climate was the dominant geological force. Icebergs began to appear in northern oceans and vast continental ice-sheets covered much of the northern continents. The North American ice cap covered 13 million square km (5 million square miles) of the continent; it carved the landscape of northern Canada, with meltwaters carrying the debris south as far as the Great Lakes.
