The Quaternary it is the last geological time period of those that make up the Cenozoic Era. It began about 2.5 million years ago and continues to the present. This is the most recent period and in it the human being has developed, so it has been studied in greater detail.
Likewise, in the Quaternary, geological activity, so active in previous periods, seems to have slowed down enormously. The movement of the continents has slowed down, as have the orogenic processes of mountain formation, a product of the collision of tectonic plates..
Most of the species, both plants and animals that inhabit the planet today, have developed during the Quaternary. However, a significant increase in species extinction has also been observed here..
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The Quaternary period began approximately 2.59 million years ago and continues to the present.
During the Quaternary period, the planet appears to have entered a period of calm, from a geological point of view. Here no great movements of the earth's crust or collisions between the different tectonic plates that exist were observed. Of course, the continental drift process has continued, but at a much slower rate than during the separation from Pangea, for example.
The Quaternary period was characterized by the decrease in environmental temperatures, which on several occasions gave rise to the so-called glaciations. During these, temperatures dropped significantly, glaciers were formed and even a large part of the continents were covered by thick layers of ice.
Ice ages were observed at the beginning of the period. Already during the Holocene there has been no significant ice age.
The Quaternary has been one of the most studied periods in the geological history of the planet, since it was in it where the first ancestors of modern man appeared.
Throughout the Quaternary it is possible to identify and recognize the different stages of human evolution, from the Australopithecus until the present Homo sapiens. Beyond the biological development of the human being, in the Quaternary it has also been possible to study the development of social skills, that is, the ability to form personal relationships and societies..
The Quaternary has also been the scene of a process of mass extinction that has been taking place in a systematic way, especially after the appearance of human beings..
At the end of the Pleistocene, most of the members of the so-called megafauna became extinct and in more recent years a large number of species of all existing phyla have disappeared from the planet..
Specialists consider that human activity is the main cause of this extinction, since human beings use different animals to obtain benefits, such as food, clothing, tool making, among others..
What has most alarmed those who have dedicated themselves to studying this phenomenon is that the species have become extinct in very short periods of time and that, at present, the list of species in danger of extinction is expanding more and more.
At a geological level, the Quaternary was a period in which there was no great activity. Continental drift, which had been a constant in previous times, seems to have lost strength.
It is true that the continental masses have continued to move, as this is a process that never ends. However, during the Quaternary the movement of the continents became slower, and they have moved only 100 km.
From this it can be correctly deduced that the position occupied by the continental masses in those times are very similar to those of today. Of course there were some variations; for example, there were some fragments of land on the earth's surface, which today are submerged and covered by the sea.
What did experience frequent changes was the sea level, because it is closely related to the presence of glaciers and melting ice. In this sense, during the Quaternary there was a lot of activity, since it was characterized by the presence of glaciations, with the consequent formation of glaciers and ice sheets on the continents..
In the first period of the Quaternary, known as the Pleistocene, there were four glaciations that affected the entire planet. During each glaciation, a large number of glaciers were formed, which greatly decreased the level of the oceans.
Between each glaciation there were periods known as interglaciers, in which part of the glaciers melted, causing a slight increase in sea level.
However, at the time when a significant rise in sea level was observed, it was during the Holocene. Here, the temperatures of the planet were increasing. Due to this, the glaciers that had formed during the Pleistocene, as well as the thick layers of ice that came to cover large areas of the continents, began to melt..
This resulted in the sea level rising considerably, even permanently covering fragments of land that, until then, had served as bridges between continents. Such is the case of the geographical area known as the Bering Strait or the English Channel, among others..
Similarly, the periods of ice ages also affected the internal bodies of water on the continents, such as the Black Sea, causing them to become bodies of fresh water during these periods. Once the glaciations were over, the sea level increased and they were again filled with brackish water.
Likewise, there were large continental areas that were covered by thick layers of ice (several kilometers thick). The great mountain ranges such as the Himalayas, the Andes and Atlas saw their high peaks covered with ice.
The geographic areas that were most frequently covered by ice were Antarctica, Canada, Greenland, part of Russia, and much of northern Europe..
Today, the rate at which sea level rises has increased, averaging 3mm per year. This has been due to the environmental phenomenon known as the greenhouse effect. This has caused the planet's environmental temperatures to increase, causing the melting of some glaciers with the consequent increase in the ocean level..
The greenhouse effect has meant a major environmental problem, since it has put the survival of habitats and species of flora and fauna at risk..
Taking into account that the distribution of the continental masses of the planet were in a position similar to the one they occupy today, it is correct to affirm that both the oceans and the seas that existed at the beginning of the period have remained until the day of today.
The Pacific Ocean has been the largest on the planet since it formed. It was only surpassed by the great Panthalasa ocean that existed during much older periods. The Pacific is located in the space between the west coast of the American continent and the east coast of Asia and Oceania. Likewise, it was and still is the deepest ocean on the planet..
Similarly, the Atlantic Ocean already existed in all its fullness. With its characteristic low temperatures, which were the result of the formation of the Isthmus of Panama during the Pliocene in the previous period.
In the southern hemisphere of the planet were the Indian and Antarctic oceans, the latter completely surrounding Antarctica.
Finally, at the northernmost tip of the planet, the Arctic Ocean, the coldest in the world, bathes the coasts of Canada, Greenland and the northwestern part of Europe..
The climate during the early Quaternary period was a continuation of the previous period, the Neogene. During this, the temperatures of the planet were decreasing notably.
In the Pleistocene, the first epoch of the Quaternary, the climate fluctuated between periods of extreme cold, known as glaciations, and others in which the temperature rose a little, called interglacial periods..
During the glaciations, the planet's temperatures dropped so much that much of the continents were covered with ice and glaciers formed in the oceans. These low temperatures notably affected the planet's biodiversity, especially in the regions most affected by ice..
In the interglacial intervals, temperatures rose a little, but not so significantly as to warm the entire planet. However, they did manage to melt the ice sheets on the continents, as well as the glaciers..
Later, towards the end of the Pleistocene and the beginning of the Holocene, the ambient temperatures were stabilizing..
During the Holocene, temperatures have not been that low. Many specialists consider the Holocene as an interglacial epoch, since, as a result of all the information they have gathered about the geological history of the planet, they affirm that a new glaciation will occur within a few million years..
At this time, ambient temperatures have turned out to be a bit warmer. However, there have been periods of time when they have dropped considerably. Such is the case of the 500 years between the fourteenth and nineteenth centuries, in which much of the planet's northern hemisphere was the victim of low temperatures. So much so that this period became known as the "Little Ice Age".
At the end of the 19th century, temperatures began to rise and stabilize and it has remained that way to this day. Of course there are areas of the planet that have maintained low temperatures, such as Antarctica and the Arctic Circle region, as well as others that have maintained a dry and arid climate, such as the center of the African continent..
During this period, life has diversified to a great extent, both at the level of plants and animals. However, one of the most important milestones has been the emergence and development of the human species.
Likewise, biodiversity has largely depended on the climate, which is why animals have developed certain characteristics to be able to adapt to a certain ecosystem..
At the beginning of the Quaternary, the fossil records show the presence of thermophilic plants, which had the ability to adapt to extreme temperature conditions. In this case, mainly to the very cold.
During the Quaternary, the appearance and development of different biomes has become evident, which have their own climatic characteristics, which largely determine the plants that will grow in them..
In this sense, the first thing that must be established is that, at present, the type of plants that are found in the greatest quantity on the planet are angiosperms, that is, those that have a protected seed.
Depending on the type of biome, there are going to be different types of plants. For example, in the biomes further north, small plants, which are highly resistant to cold, are evident, as well as lichens..
Similarly, coniferous-type plants are abundant that can also resist low temperatures..
As time progressed and the Holocene epoch began, forests and jungles began to appear, mainly at the level of the tropics. Here the specialization of plants continues to adapt to different environments. This is how plants that have the capacity to store water are observed in deserts, to counteract the lack of rainfall..
The fauna of the Quaternary period has not changed much from its beginnings to the present. Animals that have been observed since the beginning of the period and have managed to survive environmental variations have been maintained to this day. However, it is worth mentioning some important aspects.
As the period began, it became clear that mammals have been a dominant species on the planet. During the first Quaternary epoch, a group of large mammals appeared that together were called megafauna.
Among the members of this megafauna were very famous and recognized mammals, such as the mammoth, the megatherium and the saber-toothed tiger. All these had in common that his body was covered by a thick fur, to survive the cold.
Mammoths had large pointed tusks that curved upward. On the other hand, the saber-toothed tiger also had large fangs that protruded from its upper jaw and descended toward the ground..
The curious thing about this megafauna is that the vast majority of the animals that were part of it are related to current animals. For example, the mammoth is with elephants, the saber-toothed tiger with current cats, and the megatherium with current sloths..
Similarly, in the Quaternary, specifically during the Holocene, the extinction of animals has increased, mainly due to human action. Specialists argue that humans have been responsible for the systematic extinction of a great variety of animals. Globally, man has been the cause of one of the most massive extinctions ever seen in the history of the planet.
Among the emblematic animals that are extinct we can mention the dodos, the mammoths and the Tasmanian wolf, among others. At present there are many species belonging to different phyla, whose permanence on the planet is seriously threatened by human action..
Of all the groups, amphibians are the most threatened, since 30% of their species could disappear in the coming years.
One of the most relevant aspects of the Quaternary period is that it was in it that the human species emerged and evolved. From their hominid ancestors, like the Australopithecus, until the present Homo sapiens.
The Australopithecus It existed in the early Pleistocene and it is believed that it was already able to walk on two limbs. However, it was very primitive. Later the first member of the genre emerged Homo; Homo habilis, which according to the fossil records was able to manufacture and use rudimentary tools, made of stone or some metal.
Behind the Homo habilis appeared the Homo erectus, which had as its main characteristic that he could walk upright on two limbs, which allowed him to have a wide vision of the environment that surrounded him. He also knew fire and undertook migrations to other continents other than African.
The Homo neanderthalensis It was quite peculiar, since his body was adapted to the low temperatures prevailing. Likewise, with the help of the fur of hunted animals, clothing was made that protected them from the cold and the inclemencies of the environment. Almost all of the fossils of this species have been found on the European continent..
Finally modern man made his appearance, the Homo sapiens, which is established in companies that maintain a marked social hierarchy. In these, each member fulfills a specific role. His brain is fully developed, which enables him to analyze various topics and aspects and thus face complex situations.
Likewise, he was able to develop an articulated language, thanks to the development of his speech apparatus. This has allowed him to establish effective communication with his peers.
The Quaternary period is divided into two very well known and studied epochs: the Pleistocene and the Holocene..
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