Читать книгу Geology For Dummies - Alecia M. Spooner - Страница 56

A hypothesis currently being debated proposes that at some point (between approximately 600 million and 1 billion years ago) the entire planet was covered with ice. This idea is called the snowball earth hypothesis.

Some of the evidence to support this hypothesis includes rock formations that are the result of massive layers of ice (glaciers, which I describe in Chapter 13) covering the continents near the equator (at that time). Some scientists argue that an earth covered in ice could not sustain life, and there is evidence of life in rocks from both before and after the suggested time of the snowball. Others want to know what caused the snow and ice to eventually melt. Another hypothesis based on the same evidence suggests that rather than a snowball, the earth was merely a “slushball” that could have, in some areas, still supported life during an extended, very cold period.

Will the snowball earth hypothesis fade into history as a fanciful idea? Or will it be revived, perhaps proven partially true by future studies and incorporated into an accepted geologic theory? Only time (and more research) will tell.