(Answer to question 1 ) According to the Milankovitch theory, there is a 100,000-year cycle of eccentricity (departure from a
perfect circle) of Earth's orbit in three areas: the precession of equinoxes, changes in axial tilt, and
orbital eccentricity. This affects the amount of solar radiation coming in at different latitudes,
sometimes resulting in cooling.
(Answer to question 2 ) Varves are laminated silts and clays that are deposited in glacial lakes and marine waters beneath
regions of fluctuating sea ice cover. The darker layers are deposited at the end of the summer season
when the summer's life dies and becomes incorporated in the accumulating sediment. The lighter- and
finer-grained layers are deposited during the winter when the water is still, lacking abundant life, and
receiving little sediment. Thus, each light and dark pair represents one year's accumulation.
(Answer to question 3 ) Kettles are circular to oval depressions, sometimes containing small lakes, found on outwash plains,
valley trains, or end moraines. They form when a block of ice, left by a retreating glacier, is partly or
wholly buried, and then melts, leaving a depression.
(Answer to question 4 ) Moraines are landforms composed of till. End moraines are deposited by a glacier that has been in one
position for some years. It is all the till that accumulates at the glacier's terminus at the time of its
farthest advance. Ground moraines are the till that is left on the ground as the ice front recedes.
Recessional moraines are like end moraines, but they are from locations where the ice stabilized for a
time back from its farthest advance location. Lateral moraines form along the margin of a glacier.
Medial moraines develop by the coalescence of two lateral moraines when two glaciers merge
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