PLEISTOCENE: CHARACTERISTICS, SUBDIVISIONS, FLORA AND FAUNA - GEOGRAFÍA - 2024

The Pleistocene is the first geological division of the Quaternary period. It was characterized by the low temperatures that covered the planet and by the appearance of large mammals, such as the mammoth. Likewise, this time is an obligatory reference when studying the evolution of the human species, since it was during the Pleistocene when the ancestors of modern man appeared.

The Pleistocene is one of the most studied geological divisions and with the most fossil records, in such a way that the information available is quite extensive and reliable.

Typical Pleistocene landscape. Source: Mauricio Antón

General characteristics

Duration

The Pleistocene began approximately 2.6 million years ago and ended at the end of the last ice age in approximately 10,000 BC.

Little displacement of the continents

During this time, continental drift was very little and has remained that way ever since. By that time, the continents occupied the positions they currently have, in such a way that the distribution of the Earth did not undergo major modifications.

Low temperatures prevail

The Pleistocene climate was a succession of glacial cycles, which means that there were periods of glaciations, followed by others in which temperatures increased, known as interglacial periods. This was the case throughout the Pleistocene, until the end of the last ice age, known as Würn.

Much of the planet was covered in ice

According to the information gathered by specialists, approximately 30% of the planet was perennially covered with ice during this time. The areas that remained this way were mainly the poles.

At the South Pole, Antarctica was completely covered in ice, just as it is today, and at the North Pole, the lands of the Arctic Circle were also covered.

Megafauna

During the Pleistocene epoch, the great mammals such as the mammoth, the mastodons and the megatherium lived their maximum splendor, which practically dominated the landscapes of the planet. Its main feature was its large size.

Human development

In the Pleistocene, the ancestors of modern man (Homo sapiens), such as Homo erectus, Homo habilis and Homo neanderthalensis, developed.

geology

During the Pleistocene epoch there was not much activity from the geological point of view. Continental drift appears to have slowed down compared to earlier times. According to specialists, the tectonic plates on which the continents sit have not moved more than 100Km from each other.

The continents were practically already in the positions they occupy today. Even areas that are now submerged under the sea were on the surface, forming bridges between continents.

Such is the case of the area that today is known as the Bering Strait. Today it is a water channel that connects the Pacific Ocean with the Arctic Ocean. However, during the Pleistocene it was a strip of land that communicated the westernmost tip of North America with the easternmost tip of Asia.

The Pleistocene was also characterized by the abundance of the phenomenon known as glaciations, through which the planet's temperature decreased notably and a large part of the territories of the continents were covered with ice.

Specialists have verified that during this time Antarctica was completely covered by a polar cap, as is the case today.

Vision of the Earth during an ice age. Source: Ittiz

Likewise, it is known that the ice layer that formed on certain areas of the continents could reach a thickness of several kilometers, between 3 and 4 km.

Geological effects of glaciations

As a result of the many glaciations that the planet experienced during this time, the surface of the continents was affected by an erosive process. Likewise, the existing bodies of water in the interior of the continents were modified, even emerging new ones with the end of each ice age.

Decrease in sea level

In the Pleistocene, the sea level dropped dramatically (approximately 100 meters). The main cause of this was the formation of glaciers.

It is important to mention that during this time, there were a lot of glaciations, so the formation of glaciers was quite common. These glaciers caused this decrease in sea level, which would be reversed during interglacial periods.

As you might expect, when there was an ice age, the sea level dropped. When this remitted and it was in the presence of an interglacial period, the sea level increased.

This resulted in the formation of structures called by specialists as marine terraces, which have the appearance of steps on the coasts.

The study of these marine terraces has been of great importance within the field of geology, since it has allowed specialists to deduce, among other things, the amount of glaciations that have occurred.

Bodies of water during the Pleistocene

The configuration of planet Earth was very similar to what it has today. In such a way that the oceans and seas were practically the same.

This is how the Pacific Ocean was and continues to be the largest body of water on the planet, occupying the space between the American continent and Asia and Oceania. The Atlantic Ocean was the second largest ocean, located between America and the African and European continents.

Towards the south pole is the Antarctic Ocean and at the north pole the Arctic Ocean. In both the temperatures are very low and are also characterized by the presence of glaciers and icebergs.

The Indian Ocean is located in the space between the east coast of Africa and the Malay peninsula and Australia. To the south it connects with the Antarctic Ocean.

The bodies of water that did undergo certain modifications during the Pleistocene were those that were found in the interior of the continents, since, thanks to glaciations and the melting of the ice sheets that covered certain areas of the continents, lakes and rivers could be seriously modified. All this according to the evidence collected by specialists on the subject.

Weather

The Pleistocene was a geological time that, for some specialists, must be known as the Ice Age. For others, this denomination is erroneous, since in the Pleistocene a series of glaciations occurred, between which there were periods in which the ambient temperatures rose, known as interglacials.

In this sense, the climate and environmental temperatures were fluctuating throughout the time, although temperatures did not rise as much as in other periods of Earth's geological history.

The climatic conditions observed in the Pleistocene are a continuation of the climate of the previous time, the Pliocene, at the end of which the temperatures of the planet dropped considerably.

In this sense, the main characteristic of the Pleistocene climate were the glaciations that occurred, as well as the formation of thick layers of ice on the surface of the continents.

The latter was observed mainly in the strips of land closest to the poles. Antarctica was covered with ice for almost all of the time, while the northern extremes of the American and European continents were covered with ice during the glaciations.

During the Pleistocene there were four glaciations, separated from each other by interglacial periods. Glaciations are called differently on the European continent and on the American continent. These were the following:

• Günz: known by this name in Europe, in America it is known as the Nebraska glaciation. It was the first glaciation that was recorded in the Pleistocene. It ended 600,000 years ago.
• Mindel: known in the American continent as the Kansas glaciation. It happened after an interglacial period of 20,000 years. It lasted for 190,000 years.
• Riss: third glaciation of this time. It is known in America as the Illinois glaciation. It had its end 140,000 years ago.
• Würm: it is known as the Ice Age. In the American continent it is called the Wisconsin glaciation. It began 110,000 years ago and ended in approximately 10,000 BC.

At the end of the last ice age, a post-glacial period began that has lasted to the present day. Many scientists believe that the planet is currently in an interglacial period and that another ice age is likely to break out in a few million years.

Flora

Life during this time was quite diverse, despite the climatic limitations that were observed with the glaciations.

During the Pleistocene on the planet there were several types of biomes, restricted to certain areas. In such a way that the plants that were developed were those of each biome. It is important to note that many of these plant species have survived to the present day.

Towards the northern hemisphere of the planet, within the Arctic Circle, the tundra biome developed, characterized by the fact that the plants that grow in it are small. There are no big, leafy trees. A characteristic type of vegetation of this type of biome are lichens.

Another biome that was observed in the Pleistocene and that still persists is the taiga, whose predominant plant form is coniferous trees, which sometimes reach great heights. According to fossil records, the presence of lichens, mosses and some ferns was also appreciated.

Likewise, the temperate grasslands biome appeared, in which plants such as grasses were observed.

In the interior of the continents, in places where temperatures were not so low, plant forms such as large trees thrived, which later formed large forests.

It is worth noting the emergence of thermophilic plants. These are nothing more than plants that have the necessary adaptations to withstand extreme levels of temperature. As you might expect, the temperatures to which they had to adapt was cold, well below zero.

In the same vein, deciduous trees also emerged during this time, which lost their leaves in certain periods of time, especially during the coldest times.

It is important to highlight that with each glaciation that occurred, the landscape changed a little and during the interglacial periods new plant forms emerged.

Fauna

During the Pleistocene, mammals continued to be the dominant group, thus maintaining the hegemony begun in earlier times. One of the highlights of the fauna in the Pleistocene was the emergence of the so-called megafauna. These were nothing more than large animals, which were also able to withstand the low temperatures prevailing at this time.

Likewise, other groups that continued their diversification during this time were birds, amphibians and reptiles, many of which have remained until today. However, as described above, mammals were the kings of this age.

Megafauna

It was made up of large animals. Among the best known representatives of this group we can mention the mammoth, the megatherium, the smilodon and the elasmotherium, among others.

Mammut

They belonged to the genus Mammuthus. In appearance they were very similar to the elephants that exist today. As it belongs to the Proboscidea order, its most representative characteristic was the great nasal extension, which is colloquially called the proboscis, whose proper name is proboscis. Likewise, mammoths had long sharp tusks that had a characteristic curvature that oriented them upwards.

Depending on whether they were near or far from the areas with the lowest temperatures, their bodies were covered with thick fur. Their eating habits were herbivorous.

The mammoths became extinct in the following epoch, the Holocene. However, the abundant fossil records have allowed us to know a lot about this species.

Megatherium

Belonging to the order Pilosa, the Megatherium was related to the current sloths.

It was one of the largest animals that populated the earth. They had an average weight of 2.5 - 3 tons and were approximately 6 meters long. The fossils collected allow us to affirm that their bones were quite robust.

Like modern sloths, they had very long claws, with which they could dig for food. They were herbivores and are believed to have solitary habits.

Example of the megafauna. Source: DiBgd

His body was covered by thick fur that protected him from the intense cold. She lived in South America.

Smilodon

They belonged to the Felidae family, so it is considered that they were relatives of the current felines. Its most outstanding feature, apart from its large size, were the two long fangs that descended from its upper jaw. Thanks to these, the smilodon has been known worldwide as "saber-toothed tiger".

According to the collected fossils, it is believed that the males of this species could reach up to 300Kg in weight. Regarding their habitat, they lived mainly in North and South America. The site where the largest amount of smilodon fossils has been recovered is at Rancho La Brea in California, United States.

Elasmotherium

It was a large mammal, belonging to the Rhinocerotidae family, related to today's rhinos. Its characteristic element was a large horn that protruded from its skull and that sometimes could measure up to more than 2 meters.

It was herbivorous and fed mainly on grass. Like the other mammals of the time, its enormous body was covered by thick fur. It inhabited the area of ​​Central Asia and the Russian steppes.

Human evolution

During the Pleistocene the human species began to develop into modern man. The direct ancestors of the human being were Homo habilis, Homo erectus and Homo neanderthalensis.

Homo habilis was characterized by beginning to manufacture and use simple tools, probably made of stone and metal. Likewise, he built cabins and formed settlements. Their habits were sedentary.

Later, Homo erectus emerged. This had a wider distribution than that of Homo habilis. Fossils have been found not only in Africa, but also in Europe, Oceania, and Asia. They were the first to develop some sense of social coexistence. They established groups to live in society.

Homo neanderthalensis had a brain slightly larger than that of today's human being. His body developed certain adaptations to the cold. However, he resorted to his ingenuity to protect himself, making suits with animal skins. According to what is known, Homo neanderthalensis presented a certain social organization, as well as rudimentary verbal communication.

Finally, modern man, Homo sapiens, made his appearance. Its main characteristic is the extensive development that its brain reached. This has allowed him to develop activities such as painting and sculpture. Likewise, he established a society in which there is a marked social hierarchy.

Divisions

The Pleistocene is divided into four ages:

• Gelasian: began 2.5 million years ago and culminated 1.8 million years ago.
• Calabrian: it started 1.8 million years ago until 0.7 million years ago.
• Ionian: starting 0.7 million years ago to 0.12 million years ago.
• Tarantian: started 0.12 years ago and lasted until 10,000 BC

References

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