ice age on the earth

 hello, today is also a good day! don' t you think so? if NO, just hope tomrrow will be a better day!

  do you see the movies<Ice Age>?
  I like snow, but I can't image that the earth became a ice ball. can you?  So I think the earth in the ice age is the same in those movies, but not so many lovely animals.
   The Ice Age, which began about 2 million years ago, was very complex period characterized by a number of advances and with drawals of glacial ice. Most of the major glacial episodes occured during a division of the geologic time scale called  the pleistocene epoch. Perhaps the most convincing evidence for the occurrence of several glacial avdances during the Ice Age is the widespread existence of multiple layers of drift and un uniterrupted record of climate cycles perserved in seafloor sediments.
   Any theory that attempts to explain the cause of glacial ages must answer two basic questions:(1) What cause the onset of glacial condition? and (2) What cause the alternating glacial and interglacial stages that have been documented for the pleistocene epoch? Two of the many hypotheses for the cause of glacial ages involve (1) plate tectonics and (2) variation in Earth's orbit. Other factors that related to climate change during glacial ages include: change in atmospheric composition, variation in the amount of snnlight reflected by Earth's surface, and changes ocean circulation.
    Therefor, I will inrtoduce the glacier.
   
   
    A glacier is a thick mass of ice originating on land as a result of the compaction and recrystallization of snow, and it shows evidence of past and present flow. Today, vally or alpine glacier are found in mountain areas where they usually follow vallys that were originally accupied by steams. Ice sheets exist on a much larger scale, covering most of Greenland and America. In addition, covering some upland and plateaus are masses of glacial ice called ice caps. they occur in many places, including Iceland, and several of the large island in the Artic Ocean. Piedmont glacier occupy broad lowland at the bases of steep mountains and form when one or more alpine glaciers merge from the confining walls of mountain valleys.
   The average velocity of glacial movement is generally quite slow but varies considerably from one glacier to another. The advance of some glacier is characterized by periods of extremly rapid movement called surges.
   Any sediment of glacial origin is called drift. The two distinct types of glacial drift are (1)till, which is unsorted sediment deposyed directly by the ice; and (2) stratified drift, which is relatively well-sorted sediment laid down by the glacial meltwater. Also, landforms made of sratified drift.

   In addition to massive erosional and depositional work, other effects of Ice Age glacier include the forced migration of organism, changes in steam courses, formation of large proglacial lakes, adjustment of the crust by rebounding after the remorval of the immense load of ice, and climate changes caused by the existence of glaciers themselves. In the sea, the most far-reaching effect of the Ice Age was the worldwide change in the sea level that accompained each advance and retreat of the ice sheets.
    Today glaciers cover nearly 10 percent of Earth'land surface; however, in the recent geologic past, ice sheets were three times more extensive, covering vast areas with ice thousands of meters thick. So what make them disappeared? The global warming, or the pollutions, or some other thing? how do you think about it?
    we should know everything that on the earth to make our life better and live longer.