Snowball Earth is a term in geological history. It means that the surface of the earth is completely frozen from the poles to the equator, and the earth is covered with snow and ice, turning into a big snowball. There have been two snowball earth events in the history of the earth. One is that about 800 million to 550 million years ago, the earth's surface was completely frozen from the poles to the equator, leaving only a small amount of liquid water on the seabed. Another time appeared when life just appeared on the earth.
It is reported that the glaciers on the earth are in the stage of rapid melting, but some scientists believe that in ancient times, the earth once fell into a deep frozen state called "snowball earth", when the ice sheet almost completely covered the whole earth. However, the number and scope of deep freezing on the earth and the speed at which the earth becomes a snowball have always been unsolved. At present, scientists' analysis of the newly discovered rock sequence in Ethiopia is helpful to explain the "Snowball Earth" event about 765,438+07 million years ago. The results show that the "snowball earth" was formed only for thousands of years, which is equivalent to a cold current in geology.
Carol Dreulle, a geologist at Utah State University, said that the latest research based on the earth's rock records means that the snowball earth hypothesis exists, which is a major event that affects the earth's geological changes.
Geologists have suspected that the earth experienced rapid freezing in ancient times since at least the 1990s. However, although computer simulation supports this view, no substantial evidence has been found from the rock records of the earth. That's why Scott Maclennan, a Ph.D. student in geology at Princeton University, and his advisers are very excited. They got a small rock sample from Robert Bousette, a geologist at the Technical University in Berlin, Germany, which is believed to have been formed during the Snowball Earth period.
McLennan and his colleagues came to the Ethiopian town of Samre, where they met a kind of rock, which can be traced back to 765,438+0.7 million years ago and was formed by glaciers. These rocks are called "mixed rocks", which are formed by the long-distance movement of huge pebbles under the action of glaciers. Maclennan explained that under these ice age rocks are older carbonate rocks. When the ancient Romanian supercontinent was splitting, these rocks gradually formed in shallow water with the help of marine microorganisms, which indicated that the temperature in the same place was slightly higher in a longer history.
Maclennan pointed out in the June issue of Geology that, on the whole, these rock formations indicate that the ancient climate changed rapidly from a tropical paradise to a frozen wasteland. Because of the smooth transition from carbonate rocks to ice age rocks, there is no fault zone during this period, which means that there is no long-term transition between warm climate and cold climate, but it is difficult to accurately determine the completion of the ice age. He explained that the latest research shows that the "Snowball Earth" period with cold climate was formed between 1000- 100000.
Many scientists believe that such rapid ice expansion is caused by the feedback loop of ice reflectivity. During this cycle, the incident sunlight reflected by the ice sheet is reflected into space, thus lowering the atmospheric temperature. Conversely, low temperature leads to more ice layers, and as more ice layers are formed, more solar energy escapes into space. This process is like a snowball, which eventually freezes the earth completely. Droulle pointed out that there may be some changes that you can't imagine during the ancient earth period.
This discovery supports the theoretical model of snowball glacier, which shows that once the ice layer extends to 30 degrees latitude of the earth, rapid glaciation will occur around the world. At the same time, it also supports another known discovery-Stewart glacier rock in northwest Canada, and puts forward that the "snowball earth" was formed 765,438+07 million years ago. Maclennan said, considering the variability of the earth's climate history, it is not surprising that there is a "snowball earth", but the empirical test of this hypothesis theory is unexpected.
Hundreds of millions of years ago, bacteria once dominated the global ecosystem, but to some extent, a major transformation led to the evolution of complex multicellular life. According to MacDonald, during the Snowball Earth period, some species survived and evolved into new species. Snowball Earth has a shelter in the open water, or at least a shelter in the crack of ice. For example, there is life under the Antarctic ice, which makes the life of the earth continue in the ice