Snowball Earth essay

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Summary and Analysis of Paul Hoffman and Daniel Schrag 's The Snowball Earth

Paul Hoff man and Daniel Schrag 's , The Snowball Earth generally explores the theory that the world was during the Cryogenian period , which gave birth to the name snowball In addition , the also expounds on certain evidence that suggests that the Earth goes through a cycle of intense warmth and massive cooling , which implies that in the next hundred thousand years or so the planet would

once again be blanketed by ice and repeat the cycle Although Hoffman and Schrage did not actually provide any new , they explained in detail the various discoveries and studies that prove that the Earth was once exactly identical to a snowball

In their , Hoffman and Schrag explained that the main evidences which prove that the Earth was covered by ice are the presence of glacial deposits at the world 's lower latitudes , paleomagnetism , the activity of carbon and its isotopes , cap dolostones or carbonate rocks and the discovery of banded iron formations . The authors first noted Brian Harland 's observation about glacial deposits on tropical latitudes or on or near the equator , which is the warmest part of the Earth . One theory that they believe explains this wonder is paleomagnetism , which enabled these glacial sediments to exist on the equator after drifting apart from other ice-covered contitentes . They further explained that this is due to the Earth 's activity to reflect radiation , which is measured by surface albedo

Furthermore , Mikhail Budyko theorized that this albedo would cause a positive feedback that would drive the ice to the equator , causing the Earth 's surface to cool , which is believed to be the first sign that the planet was once covered in ice . Although Budyko 's model was criticized because it allegedly failed to show how the Earth recovered , Joe Kirschvink proposed that it was plate tectonics along with activity of carbon dioxide in the atmosphere that solved this problem . According to Kirschvink , even though the planet was covered in ice , plate tectonics still allowed the activity of oceanic volcanoes which caused carbon dioxide to build up to massive levels in the atmosphere . The huge amount of carbon dioxide in the atmosphere would reverse the albedo-induced ice and warm the planet

Furthermore , Hoffman and Schrag noted that another evidence of particular interest was the large concentrations of sulfides and iron oxides in glacial deposits found in the tropical latitude . Kirschvink explained that during the years that the Earth was covered in ice gas-exchange between the atmosphere and the ocean was significantly reduced , causing the deep ocean to lose oxygen . This enabled the iron to build up in significantly high concentrations and once the glaciations end , it would precipitate within the glacial deposits

Iron din . BIF associated with glacial deposits . Reduced oxygen atmosphere interaction meant iron build up in high concentrations Glacial deposits with BIF . In addition , George Williams added to...