How many separate episodes of glaciation have occurred during Earth's history?
What will be an ideal response?
There have been at least six episodes of extensive glaciation: the mid-Archean at 2.9 b.y. ago, the Huronian at 2.3 b.y. ago, the Snowball Earth episodes of the Neoproterozoic at 750 m.y. ago and at 600 m.y. ago, the Late Ordovician glaciation about 440 m.y. ago, the Permo-Carboniferous glaciations about 280 m.y. ago, and the Pleistocene glaciation, which has lasted for the past 15-30 m.y.
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Trees that keep their leaves through the winter and a ground covered with shed needlelike leaves characterize
A. chaparral. B. tropical forests. C. coniferous forests. D. temperate forests.
Landslides due to the melting of permafrost ____
a. ?are shallow and only affect a few meters as the thawed layer slides off the remaining permafrost b. ?create rotational slumps as deeper thawed areas loosen the connection of permafrost to the supporting layers c. ?are extensive and damaging, where lakes and streams warm the ground d. ?create large translational slumps as unthawed permafrost slides over subsurface meltwater e. ?can be avoided if vegetation maintains a deep snow cover
Island A is one square mile in area and has 100 species. Following the theory of island biogeography, how many species do you expect to find on the neighboring Island B that is ten square miles in area?
a. 200 b. 100 c. 50 d. 1000
Judge the following sentence according to the criteria given below: Most marine organisms are affected by the high pressure at depth BECAUSE they have large internal air pockets that can be compressed
A) The assertion and the reason are both correct, and the reason is valid. B) The assertion and the reason are both correct, but the reason is invalid. C) The assertion is correct, but the reason is incorrect. D) The assertion is incorrect, but the reason is correct. E) Both the assertion and the reason are incorrect.