Geologists have found glacier-scraped rocks over much of the planet, indicative of repeated ice ages throughout our geologic history. Dating the glaciation events is relatively easy, but determining their extent has proved more difficult because plate tectonics have shifted the continental land masses around. Recently, however, geologists from Caltech and South Africa have found a new technique to overcome this difficulty, and the results are surprising.
Using the new "paleomagnetic" technique, their studies reveal that on two occasions, 700 million and 2.2 billion years ago, ice fields stretched to within about ten degrees of the equator.
The big question such discoveries raise is this: How could Earth have escaped the runaway freezeup brought on by such extensive glaciation? Even a slight expansion of icy surface-area on Earth presents a serious problem. (Typical ice ages do not greatly extend surface ice but rather move it from one place to another, usually from the Arctic Ocean to the northern continents.) Because ice reflects solar radiation much better than does rock, vegetation, or dirt, expansion of the ice-covered region lowers global temperatures, which in turn leads to more ice production, which lowers global temperatures further, leading to still more ice production. Earth’s life forms should have been wiped out for good by the encroachment of ice into tropical latitudes.
Obviously, Earth did not freeze up and life was not eradicated. It was rescued. However, nothing less than a truly monumental heat-inducing event could have prevented this chilling seenario. Scientists see four possibilities: 1) impact by a gigantic comet or asteroid, 2) an enormous surge of volcanic eruption/s, 3) sudden and huge release of subterranean methane hydrates, or 4) some combination of these three.
In the case of the older glaciation event, evidence suggests that timely and extensive lava flows warmed the planet. Such extreme volcanic activity could have pumped enough carbon dioxide into the atmosphere to enhance the greenhouse effect, a further assist in the ice melt. Researchers continue to look for the probable cause/s of the more recent cold spell.
Whatever they discover, one message is clear: at least two times in Earth’s history, extreme-heat "calamities" occurred at just the right moment to reverse extreme-cold calamities. Both types of calamities could have destroyed life, and each might have done so had their timing been slightly different. Coincidence or plan—what seems a more reasonable conclusion?
But if these icy near-disasters were part of a divine plan, why? How could such a plan be good? Surely we cannot know the total answer, but we can see some of it. Here are some ways Earth benefits from glaciation: 1) glaciers concentrate and expose underlying mineral deposits, 2) glaciers carve out regions of fertile soil, 3) glaciers create excellent harbors (fjords) and wide, well-watered valleys, and 4) glacial movement produces some of the most beautiful scenery in the world (e.g., Yosemite Valley). Nearly global ice ages helped distribute these benefits widely.
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Facts & Faith, Second Quarter 1997 Issue