Quaternary facts for kids

Quick facts for kids Quaternary
2.58 – 0 Ma PreЄ Є O S D C P T J K Pg N ↓
A map of the world as it appeared during the Pleistocene epoch, c. 1 Ma
Chronology
Quaternary graphical timeline -2.6 — – -2.4 — – -2.2 — – -2 — – -1.8 — – -1.6 — – -1.4 — – -1.2 — – -1 — – -0.8 — – -0.6 — – -0.4 — – -0.2 — – 0 — C e n o z o i c Neogene Q u a t e r n a r y P l e i s t o c e n e ↓Holocene Gelasian Calabrian Chibanian "Late"               ← Meghalayan Northgrippian Greenlandian Subdivision of the Quaternary according to the ICS, as of 2021. Vertical axis scale: millions of years ago.
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	Base of magnetic polarity chronozone C2r (Matuyama) Extinction of the Haptophytes Discoaster pentaradiatus and Discoaster surculus
Lower boundary GSSP	Monte San Nicola Section, Gela, Sicily, Italy 37°08′49″N 14°12′13″E / 37.1469°N 14.2035°E / 37.1469; 14.2035
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 is the current geological period. It is the most recent of the three periods of the Cainozoic era. The Quaternary follows the Neogene, which is the second period of the Cainozoic.

The Quaternary began about 2.6 million years ago, and continues today. As of 2023, the Quaternary Period is divided into two epochs: the Pleistocene (2.58 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today); a third epoch, the Anthropocene, has recently been proposed, but it is not officially recognised by the ICS.

The Quaternary Period is typically defined by the growth and decay of continental ice sheets and the associated climate and environmental changes that they caused. Also, anatomically modern humans evolved. During the Quaternary, many large mammalian species became extinct. This was due to climate change and hunting by humans.

Research history

In 1759 Giovanni Arduino proposed that the geological strata of northern Italy could be divided into four successive formations or "orders" (Italian: quattro ordini). The term "quaternary" was introduced by Jules Desnoyers in 1829 for sediments of France's Seine Basin that clearly seemed to be younger than Tertiary Period rocks.

The Quaternary Period follows the Neogene Period and extends to the present. The Quaternary covers the time span of glaciations classified as the Pleistocene, and includes the present interglacial time-period, the Holocene.

This places the start of the Quaternary at the onset of Northern Hemisphere glaciation approximately 2.6 million years ago (mya). Prior to 2009, the Pleistocene was defined to be from 1.805 million years ago to the present, so the current definition of the Pleistocene includes a portion of what was, prior to 2009, defined as the Pliocene.

Quaternary stratigraphers usually worked with regional subdivisions. From the 1970s, the International Commission on Stratigraphy (ICS) tried to make a single geologic time scale based on GSSP's, which could be used internationally. The Quaternary subdivisions were defined based on biostratigraphy instead of paleoclimate.

This led to the problem that the proposed base of the Pleistocene was at 1.805 million years ago, long after the start of the major glaciations of the northern hemisphere. The ICS then proposed to abolish use of the name Quaternary altogether, which appeared unacceptable to the International Union for Quaternary Research (INQUA).

In 2009, it was decided to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.588 mya and including the Gelasian Stage, which was formerly considered part of the Neogene Period and Pliocene Epoch. This was later revised to 2.58 mya.

The Anthropocene has been proposed as a third epoch as a mark of the anthropogenic impact on the global environment starting with the Industrial Revolution, or about 200 years ago. The Anthropocene is not officially designated by the ICS, but a working group has been working on a proposal for the creation of an epoch or sub-period.

Geology

The 2.58 million years of the Quaternary represents the time during which recognisable humans existed. Over this time period there has been relatively little change in the distribution of the continents due to plate tectonics.

The major geographical changes during this time period included the emergence of the Strait of Bosphorus and Skagerrak during glacial epochs, which respectively turned the Black Sea and Baltic Sea into fresh water lakes, followed by their flooding (and return to salt water) by rising sea level; the periodic filling of the English Channel, forming a land bridge between Britain and the European mainland; the periodic closing of the Bering Strait, forming the land bridge between Asia and North America; and the periodic flash flooding of Scablands of the American Northwest by glacial water.

The current extent of Hudson Bay, the Great Lakes and other major lakes of North America are a consequence of the Canadian Shield's readjustment since the last ice age; different shorelines have existed over the course of Quaternary time.

Climate

Artist's impression of Earth during the Last Glacial Maximum

Glaciation took place repeatedly during the Quaternary Ice age. During this time, substantial glaciers advanced and retreated over much of North America and Europe, parts of South America and Asia, and all of Antarctica.

In 1821, a Swiss engineer, Ignaz Venetz, presented an article in which he suggested the presence of traces of the passage of a glacier at a considerable distance from the Alps. This idea was initially disputed by another Swiss scientist, Louis Agassiz, but when he undertook to disprove it, he ended up affirming his colleague's hypothesis. A year later, Agassiz raised the hypothesis of a great glacial period that would have had long-reaching general effects. This idea gained him international fame and led to the establishment of the Glacial Theory.

In time, thanks to the refinement of geology, it has been demonstrated that there were several periods of glacial advance and retreat and that past temperatures on Earth were very different from today. In particular, the Milankovitch cycles of Milutin Milankovitch show that variations in incoming solar radiation are a fundamental factor controlling Earth's climate.

Flora and Fauna

Large mammals in Northern areas became extinct at the end of the Pleistocene Epoch. Many forms such as sabre-toothed cats, mammoths, mastodons, glyptodonts, etc., became extinct worldwide. Others, including horses, camels and American cheetahs became extinct in North America.

The Great Lakes formed and giant mammals thrived in parts of North America and Eurasia not covered in ice. These mammals became extinct when the glacial period ended about 11,700 years ago. Modern humans evolved about 315,000 years ago. During the Quaternary Period, mammals, flowering plants, and insects dominated the land.

See also

In Spanish: Período Cuaternario para niños