b) changes in the orbital parameters of the Earth
c) volcanic activity
d) all of the above
It this a school test question? The best answer is a) insulation but the possible answers are a bit muddled for a multiple choice test. It might be best to review your notes or reading material to really understand what the teacher is asking for.
Ice ages are started by reduced insulation, that now is pretty-much accepted. The best theory is that they are started when insulation at near the Arctic circle during summer is too low to thaw the winter ice and the ice plates begin to grow.
Changes in the orbital parameters of the earth have caused ice ages, but they do so buy changing insulation. So I guess one can argue that b causes a and it is a that causes ice ages.
Volcanic activity does cause the lower atmosphere to cool but that is only over a period of years or decades. There is some evidence that the "Little Ice" was caused by a series of volcanoes over 50 years, but that is far from causing a real ice age.
My concern with a) as an answer is not knowing for certain if an ice age in earth's early history could have been caused by prolonged volcanic activity whereas the last one was not. If so, then the answer would be d) all of the above.
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Nice spelling catch by Kano. I just picked up your spelling. If that is actual spelling from the test then the answer is b). Insulation does not cause ice ages but Insolation does. Check the spelling, that may be a trick question.
Ice Age Causes and Theories
In the Pleistocene Ice Age, ice sheets originated not at the poles, but in the lower continents. The Laurentide ice sheet originated in the Hudson Bay, the Cordilleran ice sheet formed in the Canadian Rockies, the Finoscandinavian ice sheet started in Scandinavia, and the Alpine ice sheet emanated from the Swiss Alps [source: Erickson]. Ice sheets already present in Antarctica and Greenland thickened. But how did these ice sheets start? Scientists aren't sure what causes ice ages, or what combination of events might trigger another one.
It's not necessarily a matter of the world suddenly getting really cold, though. It's more that it doesn't get warm enough in the summer. In the 1920s, a mathematician named Milutin Milankovitch worked out why summers would be cooler by looking at the factors that limit sunlight's reach to Earth. He identified three factors: the tilt in the Earth's axis, the way the Earth wobbles on its axis and how close the Earth gets to the sun. By combining these factors in a mathematical formula, he was able to predict that ice ages would occur every 22,000, 41,000 and 100,000 years . These rhythms became known as Milankovitch cycles.
It seems that once it's cold, then it's likely to stay cold. Ice has albedo, or reflectivity. A higher albedo results in less absorbed sunlight because it's reflected back. This causes temperatures to drop more, so that the growth of one glacier will likely trigger more glaciers [source: Gosnell]. With cooler summers, only a little snow in the winter would be needed to offset the minimal melting.
The movement of the Earth's plates, or plate tectonics, also appears to play a role. The position of a continent affects its climate. Landmasses at high altitudes and latitudes are more likely to be cold and provide the conditions for glaciers to form. The changes caused by plate tectonics also include uplift brought on by plate collision, mountain ranges formed by plates overriding each other and oceanic trenches created by plates moving away from each other [source: Skinner]. These slow movements change the Earth's composition and could bring on the climate conducive to an ice age.
Normal cycles of the Earth.
I think you mean insolation, which is solar radiation.
The facts are no one really knows, you could include all of the above as well as tectonics (movement of the continents) and ocean currents, all could contribute.
If this test is at middle school level the answer their expecting is probably B.
http://en.wikipedia.org/wiki/Milankovitc...
If its a high school test the correct answer MAY be d
a) changes in insulation
b) changes in the orbital parameters of the Earth
c) volcanic activity
d) all of the above
