Quaternary Glaciation

Glaciers of the northern hemisphere during the Quaternary (Pleistocene) glaciation.

The Quaternary glaciation is a sequence of glaciations and interglacials of the Quaternary period, the current ice age that began about 2.58 million years ago as a part of the longer Late Cenozoic Ice Age. Among both professionals and amateurs, it is also known as simply "ice age", although in fact several other glaciations occurred in the history of the Earth. The last major glaciation (and its last phase known as the Younger Dryas) ended 11,700 years ago, and the ending of the Pleistocene epoch is associated with this event. However, the subsequent and ongoing Holocene epoch is considered an interglacial period, since the ice sheets remained in Greenland and Antarctica and their expansion may occur again in the future (but see text).

Periodization

The Quaternary glaciation is not continuous, but includes both glaciations and interglacials, which initially lasted 40,000 years, but later extended to 100,000 years. The average duration of glaciations was about 80,000 years, although the Last Glacial Period is thought to have lasted about 110,000 years. Depending on the region, different stages of glaciations are distinguished, since glaciers in different regions spreaded asynchronously. In Europe, the following recent ice ages are distinguished:

• Weichselian (115,000 to 11,700 years ago)
• Saale (400,000 to 130,000 years ago)
• Kansan (465,000 to 418,000 years ago)

Intensity

Ice age map of northern Germany and its northern neighbours. Red: maximum limit of Weichselian glacial; yellow: Saale glacial at maximum (Drenthe stage); blue: Elster glacial maximum glaciation.

Even during periods of glacial expansion, warming occurred from time to time. During periods of greatest warming, many species now living in the tropics and subtropics migrated to more northern regions. For example, hippopotamuses lived in Europe. During the Last Glacial Maximum (LGM), around 26,000 years ago, the average temperature was 6.1 °C lower than today. During the most intense glaciations, ice covers reached Newfoundland and the Netherlands. The glaciers carried with them rolled boulders. many such rocks now can be found in various places from western Europe to western Russia. During glacial periods, the large rivers were much wider than during interglacial periods, and carried more sand and gravel.

The climate was much drier than it is today, and most of the areas that are now forested were covered by savannas and steppes. The desert areas were also much larger. Because some of the ocean waters at that time were part of ice sheets, sea levels were approximately 125 m lower than today, and many of the present-day islands were part of continents. Sumatra, Kalimantan and the islands of Japan were connected to Eurasia, and between Chukotka and Alaska there was Beringia, along which the Eurasian fauna migrated to North America. Some modern coastal seas (for example, the Sea of ​​Japan) did not exist at all at that time, and the Black and Red seas had no connection with the ocean. However, some inland reservoirs increased in size as glaciers blocked rivers from accessing the Arctic Ocean. The northern part of the Caspian Sea was wider than it is today, and West Siberian Lake extended in the western part of Siberia before the LGM.

In the Holocene, there was no significant expansion of glaciers, but as a result of massive volcanic eruptions, climate cooling occurred at least twice. The first time this happened was in 536 AD, the second time (the Little Ice Age) around the 16th century.

Life during the Quaternary glaciation

The freezing of the ocean led to changes in sea currents and changes in the composition of plankton. Not all animals was able to adapt to such events. The onset of glaciation is associated with a reduction in the number of cartilaginous fish, which previously dominated ecosystems. Many whales and sirens acquired a warming subcutaneous fat layer and were able to populate even the polar regions. Blue whale, probably tha lergest animal of all time, evolved during this glaciation.

The woolly mammoth

On land, some species moved to low latitudes, while others acquired thick fur and spread to the northern territories. During the Quaternary glaciation, the Pleistocene megafauna came and extinct. Depending on the continent, this megafauna include mammoths, mastodons, woolly rhinoceroses, big cats, giant sloths and giant marsupials. Many of these species existed for hundreds of thousands of years, but became extinct in Greenlandian-Northgrippian ages of the Holocene epoch. The most likely reason for their extinction was hunting by people who appeared during the Quaternary glaciation or shortly before it. At the time of the 21st century, there is a tendency for some species to migrate to higher latitudes as global warming, also associated with human activity, intensifies.

Future

The Holocene epoch is considered an interglacial interval and, according to some forecasts, in 50,000 years the great glaciation will begin again in the northern hemisphere, as a result of which Niagara Falls will freeze and the territories of northern Eurasia and almost all of North America will be covered with ice. However, given global warming caused by human activity during the industrial era, some researchers suggest that the next phase of glaciation may begin much later (after 100,000 years), or not begin at all. The second forecast suggests that we are currently close to the end of the Quaternary glaciation, when the last glaciers in Greenland and then, probably, in Antarctica will melt completely. A more optimistic forecast suggests that the next stage of glaciation will occur, but will be weakened by current global warming.

If the current glaciation ends, the planet will experience climatic conditions that were observed in the Pliocene. It is also possible that minor ice ages (similar to the Little Ice Age of the 16th-19th centuries) caused by volcanic eruptions will occur from time to time.

In popular culture

As the most famous glaciation, the Quaternary glaciation is often featured in works of popular culture, including films and games.

• Walking with Beasts. In the last episode, events take place 30,000 years ago, when the land area in western Europe was much larger than today, since some of the sea water was in the north in the form of ice. Woolly mammoths and other Pleistocene mammals migrate south when winter comes. According to the narrator, at the time of the events almost fifty ice ages had already passed. Probably, only short glaciations of the Quaternary period are meant.
• In the Ice Age series, the main events take place 20,000 years ago, among the glaciers of Northern Hemisphere. In the first film, the main characters (Manfred "Manny", a woolly mammoth; Sid, a ground sloth; and Diego, a Smilodon), along with people and other animals, migrate south to escape the onset of cold weather. In the second film, events take place during global warming.
• 10,000 BC (2008). Part of the events of this film take place in the snowy plains of northern continents, where ancient people hunt mammoths.
• Alpha (2018). Events take place in Europe 20,000 years ago. The main character of this film tries to survive after falling from a cliff and encounters a variety of animals of the time, including bison and a saber-toothed cat.