Arctic Impressions丨Legendary Arctic Episode 5

People call the Earth the "blue planet" because the ocean accounts for a high proportion of the Earth's surface. More than 70% of the Earth's surface is covered by blue sea water. If you look at the Earth from outer space, it will appear to be a blue planet, which is very beautiful, so the Earth is called the "blue planet."

Geologists have now proposed the "Snowball Earth" theory. According to the "Snowball Earth" hypothesis, the Earth we live on has been completely covered by ice three times in its 4.6 billion years of history. At that time, the Earth was not the familiar blue "water planet", but a snowy white "ice planet". You may think this is just a magnificent and bizarre science fiction story, right? Scientists have enough evidence to show that such an unimaginable event may have really happened in the real world. So, how did this amazing hypothesis come about?

The "Water Planet" evolved from the "Ice Planet"

The first global freeze occurred during the Huronian Ice Age (2.3 billion to 2.22 billion years ago). Few strata were preserved during that period, so research was extremely difficult. So some scholars proposed that the birth of a photosynthetic algae called "cyanobacteria" had a lot to do with the reduction of greenhouse gases at that time. When the earth was first formed, there was almost no oxygen in the atmosphere. About 2.7 billion years ago, cyanobacteria appeared on the earth, large-scale photosynthesis began, and oxygen gradually appeared in the atmosphere. Oxygen can decompose methane (a type of greenhouse gas) in the atmosphere to form the same amount of carbon dioxide. However, the greenhouse effect of carbon dioxide is only about 1/24 of that of methane, so the earth began to gradually cool.

The second global freeze occurred 1 billion years after the first, and the second Sturtian Ice Age (720 million to 663 million years ago, known as the Chang'an Ice Age and the Gucheng Ice Age in China) lasted about 57 million years.
The third Marinoan glaciation (639-637 million years ago, known as the Nantuo glaciation in China) occurred almost immediately after the end of the second global freeze, but lasted for a shorter period of time.

The second and third ice ages are collectively referred to as the Neoproterozoic Glacial Age. The difference between the two ice ages and the reason why the Earth entered a global freeze again in a short period of time have not yet been explored.

A global freeze is likely to have a very important significance for the increase in oxygen concentration in the atmosphere and even for the evolution of life.
Textbooks now say that there have been at least three major ice ages around the world. The most recognized ones are the late Precambrian, the Carboniferous to Permian, and the Quaternary. There were many small-scale ice ages. The Quaternary Ice Age caused the extinction of many organisms. Organisms were mainly concentrated in vast tropical areas covered by ice and snow. Many species such as saber-toothed elephants and giant hymens disappeared. Some species such as giant pandas and metasequoia survived only in very few areas. The ice age did not cover the entire world with ice.

Some people may ask, is it possible for the Earth to freeze globally again? Scholars generally believe that this is unlikely, at least the Earth is more difficult to freeze than in the past. The Earth's temperature depends largely on the amount of solar radiation it receives, and the energy that can reach the Earth from solar radiation today is 6% higher than during the global freeze period 600 million years ago. In other words, the solar radiation reaching the Earth has increased compared to the past, so the Earth is more difficult to freeze than in the past. The poles we mentioned today may be the "fetal tracks" left by the "Ice Planet" during the global freeze period.

Author: Yu Chun

Graduated from Tsinghua University with a major in automatic control, and studied modern literature at the Graduate School of Sun Yat-sen University. He was the editor-in-chief, editor, colonel, and fourth-level professional and technical personnel of the "Navy Equipment" magazine; a director of the Third China Periodical Association, a member of the Guangdong Writers Association, a visiting professor at the Naval Command College, a naval flight safety management expert, a weapons and equipment management expert, and a senior editor.

He has been committed to literary creation, writing scientific and technological articles, holding special lectures, and engaging in the development and research of weapons and equipment, especially in the field of risk management research of high-tech equipment. His published works cover multiple fields of literature and science and technology. He has won more than 20 literary creation awards and military science and technology progress awards inside and outside the military, and has been named an advanced publishing worker of the Navy three times, and has been awarded the third-class merit three times.