Evidence of Ice Sheet Evolution
			q This figures shows a North Atlantic Ocean sediment core holds a 3 Myr d18O record of ice volume and deep-water temperature changes. q There were no major ice sheets before 2.75 Myr ago. q After that, small ice sheets grew and melted at cycles of 41,000 and 23,000 years until 0.9 Myr ago. q After 0.9 Myr ago, large ice sheet grew and melted at a cycle of 100,000 years.