Monday, November 26, 2007

Earth Changes Ice Age

Back to our History Lessons; Cycle of Ice

When have Ice Ages occurred?

Many glacial advances and retreats have occurred during the last billion years of Earth history. These glaciations are not randomly distributed in time.Instead, they are concentrated into four time intervals. Large, important glaciations occurred during the late Proterozoic (between about800 and 600 million years ago), during the Pennsylvanian and Permian (between about 350 and 250 million years ago), and the late Neogene toQuaternary (the last 4 million years). Somewhat less extensive glaciations occurred during portions of the Ordovician and Silurian (between about 460 and 430 million years ago).

During each of these intervals, many glacial advances and retreatsoccurred. For example, over 60 glacial advances and retreats have occurred during the last 2 million years.

If "ice age" is used to refer to long, generally cool, intervals during which glaciers advance and retreat, we are still in one today. Our modern climate represents a very short, warm period between glacial advances.

Mars is being hit by rapid climate change and it is happening so fast that the red planet could lose its southern ice cap, writes Jonathan Leake.

Scientists from Nasa say that Mars has warmed by about 0.5C since the 1970s. This is similar to the warming experienced on Earth over approximately the same period.

Since there is no known life on Mars it suggests rapid changes in planetary climates could be natural phenomena................

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