Pub. date: 2008 | Online Pub. Date: April 25, 2008 | DOI: 10.4135/9781412963893 | Print ISBN: 9781412958783 | Online ISBN: 9781412963893| Publisher:SAGE Publications, Inc.About this encyclopedia
IN THE EARLY 1960s, Brian Harland, a geologist at Cambridge University, observed that rocks on several continents, dating from the Neoproterozoic era (approximately 800–680 million years ago), contain glacial debris. Some of the glacial debris included carbonate rocks, which are known to form in the tropics (e.g., in the present-day Bahama Banks). This conclusion later gained additional support from paleo-magnetic data. One potential explanation is that the Earth entire Earth was covered by ice and snow during the Neoproterozoic. This has come to be known as the “Snowball Earth” hypothesis. One early problem was understanding how a global ice age could have commenced. During the 1960s, the Russian climate scientist Mikhail Budyko used a computer simulation to establish that a runaway ice-albedo feedback effect could lead to global glaciation. The term albedo refers to the amount of the sun's energy that is reflected by the Earths surface. As glaciers grow ...