when a world froze

By Fabrcio Caxito

From Bahia to Mato Grosso, operating system records about a glacial period over635 millions over years ago


Images of hominids crossing a strait over Bering between Asia electronics and America, gigantic mammoths electronic stretches on ice that went carry out North Pole from New York often come to mind when we hear about the carry out ice age. This moment, however, only part perform glacial period in which the planet is living last, started they would about 2.6 million over years yes, we continue in an ice perform period, t that we are in one over its interglacial periods. However, in its 4.5 billion years of history, the Earth has gone through much more extreme climate change situations. In at least some of these episodes, the polar caps spread almost to the equator, freezing the planet almost completely. These therefore moments called Terra Bola de Neve.

The best characterized Earth Bola sobre Neve occurred they would have approximately millions over years, during the glaciation Marinoana, marco perform fim perform Cryogenian period that received its name (Greek perform kros, cold) due to the abundance of glacial deposits found around the world. The study of these rocks provides very important clues to understand the climatic evolution of the planet.

How to recognize operating system records about an ancient glacial period? When traversing operating system continents, glaciers, capable of moving at speeds of up to a kilometer per year, tear off chunks of rock. Such fragments, wrapped in ice, detach from the primary mass, transforming themselves into icebergs that, in turn, move away thousands of kilometers from the mainland. In the ocean, as operating system icebergs melt, operating system pieces of rock embedded in the ice (electronic collected on land) break free. One of these easier ways to identify ancient glacial events is to look for these dropstones, or clasts dripping from exotic fragments, different from everything around them, stuck in the thin mud over deposits on the bottom perform the sea.

Interestingly, this type on rock of the same age can be seen in several perform regions in Brazil, such as in Chapada Diamantina baiana, in Serra perform Espinhao mineira electronic in the mountain region perform Mato Grosso. Most interestingly, however, therefore operating system deposits found logo design above diesels marine rocks containing dropstones: these are carbonates, typical of hot climates, present today only in the seas close to the equator, as in the Bahamas diesel bank. How is it possible the existence of rocks under hot climate directly in contact with rocks under glacial climate?

The theory of an Earth Ball over Snow, which gained zero strength last performance with a work 2 american scientists Joseph Kirchvink electronic Paul Hoffman, electronic from a team led by the latter. One of his hypotheses is that, during the period of glaciation, the entire planet, including the surface of the 2 seas, was covered by an ice cap. Under normal conditions, operating system gases generated inside the Earth electronic are expelled by the electronic consumed therefore volcanoes and reabsorbed by the ocean. In a Snowball-type perform situation, however, the exchange of gases is practically interrupted due to the layer of ice interposed between the electronic operating system atmosphere and the oceans. The atmosphere is increasingly concentrated in gases expelled by volcanoes, among which the CO2 electronic and the methane operating system, which cause the greenhouse effect.

Terra Bola de Neve brings, therefore, in itself , the seed of its ruin, as the accumulation of gases in the atmosphere leads to a period of extreme greenhouse effect that melts the ice layers and causes the carbonate rocks in a warm climate to deposit on the glacial rocks.

The study of old Snowball episodes can tell us a lot about periods of intense climatic variation (both for the cold and for the hot) that our planet has gone through, and may pass again in the future.


Fabrcio Caxito professor of geology and philosophy student at UFMG.

This text is a continuation of the article When the serto was sea, by the same author.

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