CENOZOIC ERA: CHARACTERISTICS, PERIODS, GEOLOGY, FLORA - GEOGRAFÍA - 2025

The Cenozoic Era, known as the Tertiary until a few decades ago, is the last era into which the history of the Earth has been divided since its appearance. It began about 65 million years ago and continues to the present day. The name comes from the Greek and means life or new animal.

This stage, which falls within the Phanerozoic eon, began with a planetary catastrophe that caused the extinction of up to 75% of the animal species of the time, including dinosaurs. The most widespread theory is that the cause was the fall of a large meteorite.

Source: By Heinrich Harder (1858-1935), via Wikimedia Commons

After the winter caused by this meteorite, the remaining animals took the place left by the previous ones. Mammals benefited from this event, and they became the dominant ones on the planet.

It was also during this Era that the continents acquired the shape they have today. The oceans expanded and new mountains appeared.

However, from the human perspective, the most important event that occurred has been the appearance of the first hominids, which evolved into Homo sapiens, the current human being.

characteristics

The first to use the term Cenozoic was John Phillips, a British geologist. The word, which means "new life" in Greek, came to replace the previous Tertiary Era designation to describe the last part of the planet's history.

The Cenozoic Era began approximately 65 million years ago and continues today. In it, the terrestrial surface finished being ordered as it is today. Likewise, it was when the human being appeared on the planet along with most of the current animals.

The previous era, the Cretaceous Period, ended with a great extinction event. Dinosaurs that were not birds and many other species disappeared from the face of the Earth.

Era of changes

Scientists regard the change between the Cretaceous and Cenozoic as a time of global change. It all started with the event that caused the aforementioned extinction. Although the cause is not known with certainty, the hypothesis that has the most followers is the impact of a meteorite against Earth.

That fact caused the Cenozoic to be totally different from previous periods, without there being a continuous evolutionary line. Instead, there is a big jump from one time to another that affects fauna, flora and even climate.

For their part, the continents that had broken off from the primeval Pangea continued to disperse. Some land masses collided, forming, for example, the Alps.

Weather

This era is characterized by being a period of slow cooling, over the millennia. In its beginning, the particles launched into the air by the meteorite that caused the great extension completely blocked the solar radiation. This caused winter years, without the heat reaching the surface in conditions.

Later, due to geological events that led to the appearance of the Antarctic Circumpolar Current, it caused the ocean to radically cool.

This drop in temperatures had a small stop during the Miocene. However, the union of South America with North America caused the Arctic region to cool down due to its effect on sea currents. Then the last glacial maximum occurred.

Neogene

The cooling continued during the Neogene, the second substage into which the Cenozoic Era is divided. It was especially important in the Northern Hemisphere, which saw its vegetation change to adapt to the climate.

Throughout the Neogene, the planet's inhabitants had to evolve to survive low temperatures. Large hairy animals appeared, such as the mammoth or the woolly rhinoceros.

At this stage, the land orography also underwent several changes. The collision of the continental plates caused great mountain ranges to appear. Thus, Spain and France were united, forming the Pyrenees during the process. Italy joined the rest of the continent, while India continued to float to Asia.

Already in the Quaternary, the current Cenozoic stage, the ice has remained at the Poles, although the climate has gradually warmed up. This melted part of the previously existing ice, creating a connection between North and South America.

The age of mammals

One of the nicknames by which the Cenozoic is known is the Age of Mammals. During the previous stage, only a few species existed. The extinction caused by the meteorite and other circumstances caused the number of mammals to increase enormously.

Fish and birds also evolved in this Age. In fact, all the species that exist today appeared in it, not counting a few descendants of the ancient dinosaurs mainly.

In terms of flora, the most widespread plant formation during much of the Cenozoic was the shrubby savanna.

Tectonics

As explained before, it was during the Cenozoic era that the continents reached their current positions and shapes.

India, which was floating at high speed, ended up colliding with Asia. The brutality of the crash caused the highest mountains on Earth to appear, in the Himalayas.

Antarctica veered toward the south pole, while South America slowly joined with North America. This smoothness avoided the creation of mountains and, instead, the appearance of the Isthmus of Panama.

The Atlantic Ocean expanded in size as Europe and America continued to separate. Finally, Arabia collided with Eurasia, also softly.

Periods (subdivisions)

The Cenozoic Era is usually divided into three different periods: the Paleogene, the Neogene, and the Quaternary. Formerly, it was called the Tertiary Period, as part of the already abandoned scientific nomenclature of dividing the history of planet Earth into four periods.

Paleogene period

It began 65 million years ago and lasted until 23 million years ago. It is divided in turn into the Paleocene, Eocene and Oligocene eras.

During the 42 million years of the Paleogene, the great evolution suffered by mammals from small and unimportant previous species stood out. Part of the changes affected the size of the species, which grew considerably.

The specialists consider this period like one of transition in terrestrial history. The planet got quite cold, especially in the polar regions. Large mountain ranges appeared, such as the Rockies in North America or the Alps, the Pyrenees or the Cantabrian Mountains in Europe.

Some animals that emerged and diversified in the Paleogene were equids, ancestors of today's horses. The existence of monkeys also stands out. In the ocean, for its part, species such as angiosperms or taxa, still existing, were maintained.

Neogene

The second subdivision of the Cenozoic was the Neogene. Researchers distinguish two stages in this period: the Miocene, which began 23 million years ago, and the Pliocene, which began 5 million years ago.

Birds and mammals continued their development, approaching the species that exist today. Other animals, on the other hand, were quite stable.

There were fewer plate movements than during the previous period, although this does not mean that they stopped completely. The climate continued to cool down, a process that would culminate later in the ice ages.

As an important point, in the Neogene the first hominids ancestors of the human being appeared.

Quaternary Period

It is the period in which the Earth is currently. It began 2.59 million years ago and the most prominent element was the appearance of Homo sapiens on the planet.

Some large species became extinct, both in the animal and plant kingdoms. Definitely, mammals and birds became the dominant animals on Earth.

The flora and fauna was almost the same as it is today and large migratory movements of many species, including humans, took place.

geology

During the Cenozoic, there were many changes in the earth's crust that would end up giving the planet the geography it presents today.

Among the most notable events are the expansion of the Atlantic Ocean and the great collision of India with Asia, which would eventually give rise to the Himalayas.

Likewise, the African tectonic plate continued its advance towards Europe until it formed the Alps. The same cause, the collision of plates, caused the North American Rocky Mountains to emerge.

Cenozoic rocks

Cenozoic rocks developed extensively on all continents. They were especially numerous in the plains located in the lower lands, such as the Gulf.

These types of rocks have not reached the consolidation that the older ones present, although the high pressure caused by deep burial and the high temperatures may have hardened them. This phenomenon is called metamorphism.

During the Cenozoic it appears in predominance of the sedimentary rocks. In this type of stone, more than half of the planet's oil reserves have been formed.

On the other hand, igneous rocks are represented by flood basalts. Also by the volcanoes located in the Circle of Fire (Pacific Ocean) and in the oceanic islands, such as Hawaii.

Deglaciation on the continent

In the Cenozoic there has been a phenomenon that has changed the orientation of the poles. On the one hand, Antarctica remained centered on the South Pole, but the northern continental masses were converging towards that same cardinal point.

The Antarctic continent has been undergoing a deglaciation that began about 35 million years ago, while the same phenomenon began in the northern hemisphere only 3 million years ago.

The remains of this process can be seen in moraine glaciers, for example. Also at the bottom of the ocean there are traces of this warming.

Flora

The main characteristic of the flora during the Cenozoic Era was the development of frond trees and phanerogamic plants. In addition, there was the appearance of a great variety of plant species with characteristics that allowed rapid adaptation to the environment.

The hominids took advantage of the existence of fruit trees, palms and legumes, which offered them food that was easy to obtain.

Increased diversity

As with the fauna, the Cenozoic represented a great change in the varieties of flora with respect to the previous Mesozoic. Many of the plants were angiosperms, with flowers, which allowed for much greater expansion.

One aspect that marked the flora of that period was the climate. This began to differentiate by areas of the planet, making the same happen with trees and plants. Thus the local varieties of each species were born.

Some adapted to cooler areas, while evergreens were more common in the tropics and nearby areas.

Fauna

As explained before, the changes in the fauna during the Cenozoic were many and very important. The Age had begun with the mass extinction caused by a meteorite. Not only did the dinosaurs disappear from the planet, but also many other varieties of animals.

Much of this extinction was caused by the effects of the fall in the atmosphere. The dust that rose into the air prevented sunlight from reaching the ground, killing many plants first. The result was that the entire food chain was thrown out of balance and almost 75% of life disappeared from Earth.

When the Cenozoic arrived, and with the great rulers disappeared, there was a great diversification of life forms. It was the mammals that evolved most efficiently to dominate the planet.

For its part, the expansion of the oceans also had an effect on marine fauna. In this case, whales, sharks and other aquatic species proliferated.

Mammals

The numbers are enough to show how mammals replaced the great saurians as the most important animals. At the beginning of the Cenozoic, there were only 10 families of mammals. In just 10 million years, little on an evolutionary scale, they became 80.

Regarding modern mammals, many of them appeared in the Oligocene, between 35 and 24 million years ago. The greatest diversity occurred between 24 and 5 million years ago, in the Miocene.

The human being

The animal that was called to become the true ruler of the Earth also appeared in this Age. It is about the genus Homo, which evolved into Homo sapiens, the modern human being.

The first hominids date from the Pliocene. It was not a linear evolution, but different species appeared. Some had phylogenetic relationships (they descended from each other), but there were also independent ones.

Australopithecus, Homo habilis or Homo erectus are some of these human ancestors. At first they were quadrupeds, but over time they became bipeds. Likewise, they lost their hair and began to make tools.

One of the most important moments in this evolution, according to the experts, was the introduction of greater amounts of meat in the diet. Increased consumption of higher-quality protein and nutrients increased brain power, making hominins smarter.

H. sapiens appeared about 50,000 years ago, although it would still take much longer for it to learn to communicate and develop cultural and coexistence communities.

References

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