SNOWBALL EARTH 1
Global glaciations occurred due to the long periods of isolation andextreme environments on a snowball earth (Hoffman & Schrag,2000). The plate tectonics viewpoint explains how the planet’sthin, rocky skin was broken into giant pieces. Subsequently, thelatter segments moved atop a distinct mass of hotter rock below.During a global glaciation, shifting tectonic plates wouldcontinually build volcanoes and release carbon dioxide into theatmosphere (Hoffman & Schrag, 2000). Furthermore, some physicaland chemical mechanisms would drive the earth into a deep-freeze. Forexample, liquid water required to erode sedimentary rocks and burythe carbon would be trapped within the mass of ice (Hoffman &Schrag, 2000). Consequently, the carbon dioxide would accumulate tohigh levels. Contrariwise, a low concentration of carbon dioxide wassufficient to cause a deep-freeze on the earth.
On the other hand, the earth could have reversed the deep-freeze andentered a global hothouse state. In this regard, extreme greenhouseconditions would have led to the development of thick sequences ofcarbonate rocks. Such hot and humid conditions would be particular tothe transient aftermath of a snowball earth (Hoffman & Schrag,2000). An ultrahigh level of carbon dioxide would be needed in theatmosphere to raise temperatures if the earth froze over. Notably,the temperatures had to match the melting point at the equator. Theonset of melting was accompanied by the replacing of high-albedo icewith low-albedo seawater (Hoffman & Schrag, 2000). Consequently,the runway freeze would be reversed. Similarly, resumed evaporationwarms the atmosphere because water vapor acts as a powerfulgreenhouse gas (Hoffman & Schrag, 2000). Subsequently, a massivereservoir of atmospheric moisture could create and enhanced watercycle. Torrential rainfall would also eliminate some of theatmospheric carbon dioxide in the form of carbonic acid (Hoffman &Schrag, 2000). Therefore, the snowball earth could enter into aglobal hothouse state.
Hoffman, P. F., &Schrag, D. P. (2000). Snowball earth. Scientific American,282(1), 68-75.