Glacial theory and glacial period

* In the 20th century, geologists determined that a complex glacial process had occurred on Earth. Studies of ocean floor sediments determined that glacial/interglacial cycles had occurred approximately every 100,000 years.

* The glacial period, began about 2 million years ago, was in the period of the Earth known as the Pleistocene (although studies show that the Antarctic ice cap is 14 million years old). It was a very complex period characterized by advances and retreats of the glacial ice. At this time ice covered 30% of the Earth's surface.

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THE EFFECTS OF THE ICE AGE WERE:

·          / The volume of glacial ice increased to 70 million km3, 45 million more than today.

·          /  Huge erosion and deposition.

·          /  Migration and forced adaptation of living beings: many animals and plants had to adapt, migrate or became extinct.

·       / Changes in the watercourses: the current routes have nothing to do with the pre-glacial ones.

·        / Readjustment of the earth's crust: one effect produced by the ice was the lifting of the earth's crust because the weight of the cap glaciers caused the crust to bulge downwards. Once this icy mass disappeared, the Earth's crust readjusted by gradually lifting.

·        / Climate change on the planet: the glacial period modified the climate and thus many arid or semi-arid zones. This colder and more humid climate generated pluvial lakes with large areas and great depth. As the ice age wore off, these great lakes dried up.

·          / Change in the level of the planet's sea: during the glacial period there was a great drop in sea level, up to 100 meters below the current level. As this period ended, a rise in sea level took place.

CAUSES OF ICE AGES: There is no generally accepted theory to explain the causes. There are two hypotheses:

1.- TECTONIC PLATES: Today's continents were united into a single supercontinent called Pangea. This land mass separated and created the current continents. All these plate movements were responsible for climatic changes. Changes were generated in the oceanic circulation, which altered the planetary climate and this gave rise to various glaciations on the planet. This cannot explain the alternation of interglacial and glacial climate that occurred in the Pleistocene, since the movement of plates is very slow (a few centimeters/year).

2.- VARIATIONS OF THE EARTH'S ORBIT: The variation of the orbit produces a variation of the solar radiation and this generates changes in the terrestrial climate. A decrease in the solar radiation received by the planet produces changes in the terrestrial seasons. Thus there would be longer winters, with higher total snowfall, and milder summers, with reduced snow melt. Researchers have shown that the glacial periods of the Quaternary coincide with changes in the Earth's orbit. This hypothesis would explain the glacial/interglacial changes of the Pleistocene.This hypothesis was developed and defended by the Serbian scientist Milankovitch. Below we can see a video about this.