According to geologists, if there is any part of the Earth’s surface covered by ice, we are already living in an ice age. This is what happens today, with about 10% of the planet under glaciers and glaciers (at the height of a glaciation, however, this proportion reaches 30%). The evidence is that, during most of its existence, the planet had an average temperature of 8 to 15 degrees Celsius above the current one, enough heat for no area of the Earth to remain frozen. In the last billion years, however, the Earth has gone through five glacial periods. The current one would be the sixth, having started about two million years ago. But, within a glacial period, the temperature is not always the same. For every 100,000 years of very cold weather, we have about 10,000 years of cool weather. We are 8,000 years into one of those less icy periods. It is believed that between 2000 to 4000 years from now, a new expansion of the ice sheet will begin.
Science still hasn’t figured out what exactly causes the planet to enter an ice age. But there are some theories that try to explain the alternation between colder and warmer phases within a glaciation. The most accepted is based on the various changes that occur in Earth’s orbits. First, Earth’s axis of rotation does not form a perfect 90-degree angle with the equator: the planet is tilted slightly. The angle of this inclination undergoes changes due to the influence of the gravitational force of the other planets. This is one of the changes. Second, the axis of rotation also rotates around itself as if it were a top, due to the attraction of the Sun and Moon. Third, the movement around the Sun is not always the same, also due to the force of gravity of the planets. The set of these changes causes a variation in the amount of energy arriving from the Sun, causing cooling.
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– What is dry ice?
– How long did the last ice age last?
Expansion and retreat of glaciers on Earth The current glaciation of the planet reached its peak 20,000 years ago
Currently, about 10% of the Earth is covered in ice.
20,000 years ago, 30% of the planet was frozen
In the worst ice age ever – 800 million years ago – glaciers came close to the Equator
1. Human Aurora
Since the emergence of the first human beings – about two million years ago – the Earth has been going through an ice age.
2. Overseas Exodus
Around 12,000 years ago, man was able to migrate from Asia to America due to the freezing of the sea between the two continents, in the Behring Strait
3. Big game
Upon arriving in America, humans found large mammals, hitherto unknown – such as mammoths and saber-toothed tigers – living in savannas, south of the glaciers.
4. Total Extermination
It took approximately 2,000 years for hunting to lead to the disappearance of the giant mammals – with the extinction of 33 animal genera in all
The hunting of mammoths and saber-toothed tigers made both species extinct.