Quaternary facts for kids
Quick facts for kids Quaternary |
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| 2.58 – 0 Ma | |
A map of the world as it appeared during the Pleistocene epoch, c. 1 Ma
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| Chronology | |
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Quaternary graphical timeline
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Subdivision of the Quaternary according to the ICS, as of 2021.
Vertical axis scale: millions of years ago. |
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| Etymology | |
| Name formality | Formal |
| Usage information | |
| Celestial body | Earth |
| Regional usage | Global (ICS) |
| Time scale(s) used | ICS Time Scale |
| Definition | |
| Chronological unit | Period |
| Stratigraphic unit | System |
| Time span formality | Formal |
| Lower boundary definition |
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| Lower boundary GSSP | Monte San Nicola Section, Gela, Sicily, Italy 37°08′49″N 14°12′13″E / 37.1469°N 14.2035°E |
| Lower GSSP ratified | 2009 (as base of Quaternary and Pleistocene) |
| Upper boundary definition | Present day |
| Upper boundary GSSP | N/A |
| Upper GSSP ratified | N/A |
| Atmospheric and climatic data | |
| Mean atmospheric O2 content | c. 20.8 vol % (104 % of modern) |
| Mean atmospheric CO2 content | c. 250 ppm (1 times pre-industrial) |
| Mean surface temperature | c. 14 °C (0 °C above modern) |
The Quaternary Period is the time we live in right now! It is the newest part of the Cainozoic Era, which is a huge chunk of Earth's history. This period came after the Neogene Period.
The Quaternary Period started about 2.58 million years ago and is still going on today. It is split into two main parts, called epochs:
- The Pleistocene Epoch: This lasted from 2.58 million years ago to 11.7 thousand years ago.
- The Holocene Epoch: This started 11.7 thousand years ago and continues to the present day.
Some scientists also talk about a third part called the Anthropocene. This name is for the time when humans have had a big impact on the planet. However, it is not yet officially recognized by the International Commission on Stratigraphy (ICS).
The Quaternary Period is famous for huge ice sheets growing and shrinking. These changes caused big shifts in climate and the environment. It's also the time when modern humans first appeared. Many large mammals also died out during this period. This happened because of changes in the climate and hunting by humans.
Contents
How Scientists Study the Quaternary Period
Early Ideas About Earth's Layers
In 1759, a geologist named Giovanni Arduino suggested that the layers of rock in northern Italy could be divided into four main groups. Later, in 1829, Jules Desnoyers used the word "quaternary." He used it for sediments in France that looked much younger than the older Tertiary Period rocks.
The Quaternary Period starts after the Neogene Period and continues to today. It includes the time of many glaciations (ice ages) during the Pleistocene. It also includes our current warmer time, the Holocene.
Defining the Start of the Quaternary
Scientists decided that the Quaternary Period began when large ice sheets started forming in the Northern Hemisphere. This was about 2.6 million years ago. Before 2009, the Pleistocene was thought to start at 1.805 million years ago. This means the current definition of the Pleistocene now includes a part of what was once called the Pliocene.
For a long time, scientists studying the Quaternary used different ways to divide time in different regions. In the 1970s, the International Commission on Stratigraphy (ICS) wanted to create one global timeline. They tried to base it on specific points in rock layers, called GSSPs.
This caused a problem because the proposed start of the Pleistocene was much later than the beginning of the big ice ages. The ICS even thought about getting rid of the name "Quaternary" entirely. But the International Union for Quaternary Research (INQUA) disagreed.
In 2009, they decided to keep the Quaternary as the youngest period of the Cenozoic Era. Its start was set at 2.588 million years ago. This included a stage called the Gelasian, which used to be part of the Neogene Period. This date was later slightly changed to 2.58 million years ago.
The Idea of the Anthropocene Epoch
The Anthropocene has been suggested as a third epoch within the Quaternary. This name highlights the big impact humans have had on the planet. It is often thought to start around the Industrial Revolution, about 200 years ago. The ICS has not yet officially approved the Anthropocene. However, a group of scientists is working on a proposal for it.
Earth's Changing Geography During the Quaternary
The 2.58 million years of the Quaternary Period is the time when humans, as we know them, have existed. During this time, the continents have not moved much due to plate tectonics.
However, there have been some major geographical changes:
- The Bosphorus Strait and Skagerrak appeared during ice ages. They turned the Black Sea and Baltic Sea into freshwater lakes. Later, rising sea levels flooded them, making them salty again.
- The English Channel sometimes became dry land, connecting Britain to Europe.
- The Bering Strait also closed at times, forming a land bridge called Beringia between Asia and North America.
- Huge floods from melting glaciers created the Channeled Scablands in the American Northwest.
Today's Hudson Bay, the Great Lakes, and other big lakes in North America are still changing. This is because the land, called the Canadian Shield, is slowly rising after the weight of the last ice age glaciers melted away.
Quaternary Climate: Ice Ages and Warm Spells
During the Quaternary Period, Earth went through many ice ages. Huge glaciers grew and then melted back. This happened across much of North America, Europe, parts of South America and Asia, and all of Antarctica.
In 1821, a Swiss engineer named Ignaz Venetz noticed signs that glaciers had once been far from the Alps. Another Swiss scientist, Louis Agassiz, first doubted this idea. But when he tried to prove it wrong, he found that Venetz was right! A year later, Agassiz suggested there had been a huge ice age that affected the whole world. This idea made him famous and led to the "Glacial Theory."
Over time, with better geology, scientists learned there were many periods of ice advance and retreat. They also found that Earth's past temperatures were very different from today. Scientists like Milutin Milankovitch showed that small changes in how much solar radiation Earth receives are key to controlling our planet's climate. These are known as Milankovitch cycles.
Quaternary Life: Plants, Animals, and Human Evolution
Animals of the Ice Age
Many large mammals in northern areas died out at the end of the Pleistocene Epoch. Animals like sabre-toothed cats, mammoths, mastodons, and glyptodonts disappeared worldwide. Other animals, including horses, camels, and American cheetahs, became extinct in North America.
The Great Lakes formed during this time. Giant mammals lived in parts of North America and Eurasia that were not covered by ice. These large animals died out when the last glacial period ended about 11,700 years ago.
Humans and Other Life Forms
Modern humans first appeared about 315,000 years ago. During the Quaternary Period, mammals, flowering plants, and insects became the main types of life on land.
See also
In Spanish: Período Cuaternario para niños
