81.   To some scientists, this raises the possibility that inland ice sheets might behave likewise, causing sea level to rise more rapidly than scientists have anticipated.

82.   When the ice sheet retreats, land that has been compressed by the massive ice sheet rises up and large amounts of previously submerged sea life dies off.

83.   When the tilt angle is low, less sunlight hits the high latitudes of the Northern Hemisphere in summer, less ice melts and ice sheets expand.

84.   When less sunlight falls there, less snow melts in summer and over time is compressed to form growing continental ice sheets.

85.   When the great ice sheets advanced and retreated, the ranges of countless creatures, not to mention entire forest and grassland ecosystems, moved with them.

86.   Whether the ice sheet will forever stay that way no longer seems such a bed-rock certainty.

87.   While the research does not show how all that ice was distributed, it does indicate that the ice sheets reached some level of equilibrium and stability.

88.   With the bigger ice sheet, the European players turned it into a game of passing and skating.

89.   All World Cup games will be played on the smaller ice sheet.

90.   As it retreated toward the poles, the ice sheet left in its wake at least two lakes containing more water than the Great Lakes combined.