Earth was a slushball

An extraordinary episode of global cooling hundreds of millions of years ago that some experts say caused Earth to completely freeze over has been miscalculated, a new study says. Instead of "Snowball Earth," the planet really became "Slushball Earth," its authors suggest. The great chill - the longest and deepest ice age in Earth's known history happened during the late Neoproterozoic era, 850 to 542 million years ago. The evidence for the Snowball thesis comes from deep sediments in the ocean. Scientists look through these layers to measure levels of the isotope carbon 13 (C13), deposited in plants through photosynthesis, as a telltale of Earth's climate.

Above and below the Cryogenian layer is an abundance of C13. But the Cryogenian layer has negligible levels of this isotope. The explanation is that Earth froze over completely and glaciers crept down into the tropics, possibly even reaching the equator. The brilliant white shell reflected back the Sun's rays, and thus its heat, so well that the Snowball persisted for nearly 200 million years. Eventually the greenhouse gas carbon dioxide (CO2), welling up from volcanoes, escaped into the air and thankfully set the planet onto a warming trend, and so the icy blanket was melted.

Image and Article source: Deccan Chronicle