Quaternary

The Quaternary is the current and most recent period in Earth's long history. It is part of the Cenozoic Era and follows the Neogene Period. The Quaternary began about 2.6 million years ago and continues today.

This period is divided into two main parts, called epochs. The first is the Pleistocene, which lasted from 2.6 million years ago until about 12,000 years ago. The second is the Holocene, which started around 12,000 years ago and is the time we live in today. There was a proposal to add a third epoch called the Anthropocene, but it was not accepted in 2024.

The Quaternary is well known for its big changes in climate, especially the growth and shrinking of large ice sheets covering parts of the continents. These changes were linked to natural patterns in Earth's orbit and tilt, called Milankovitch cycles, and they had major effects on the world's environment and the living things around us.

Research history

In 1759, a scientist named Giovanni Arduino said that rock layers in northern Italy could be grouped into four types. Later, in 1829, another scientist, Jules Desnoyers, used the word "quaternary" to describe newer rock layers in France near the Seine River.

The Quaternary Period comes after the Neogene Period and continues until today. It includes times when large glaciers covered parts of the Earth, called the Pleistocene, and the current warmer time, called the Holocene. The Quaternary began about 2.6 million years ago when glaciers first started forming in the north.

Scientists have worked to create a single timeline that can be used all over the world. In 2009, they set the start of the Quaternary at 2.58 million years ago. There was a suggestion to call a new recent time the Anthropocene because of big changes people made to the Earth, but this idea was not accepted in 2024.

Geology

The last 2.58 million years, called the Quaternary, is when humans lived. During this time, the positions of the continents changed very little because of moving plates under the ground.

We know more about what happened during the Quaternary than earlier times because more information from this period has been saved. Big changes happened, like the Bosphorus and Skagerrak waterways opening up, turning the Black Sea and Baltic Sea into lakes before they filled with sea water again. Sometimes, land connected Britain to the rest of Europe through the English Channel, and the land bridge between Asia and North America closed when the Bering Strait froze over. Huge floods also poured over the Scablands in the northwest United States from melting glaciers. Today’s Hudson Bay, Great Lakes, and other big lakes in North America look the way they do because the land, called the Canadian Shield, shifted after the last ice age.

Climate

The climate during this time had many periods when huge glaciers moved from the poles to places far north and south. These icy times are called Ice Ages. They happened many times during the Quaternary Period, which started about 2.58 million years ago and continues today.

A Swiss engineer named Ignaz Venetz suggested that glaciers had moved far from the Alps. At first, another scientist, Louis Agassiz, disagreed, but later he proved Venetz was right. Agassiz then proposed that Earth had gone through a long glacial period, which made him very famous.

We now know there were many times when glaciers grew and then melted away. The land and temperatures on Earth were very different from today. One important idea is that changes in the amount of sunlight reaching Earth help control its climate. During this time, big glaciers covered parts of North America, Europe, South America, Asia, and all of Antarctica.

Flora and fauna

Main article: Late Pleistocene extinctions

Many large animals, like sabre-toothed cats, mammoths, and mastodons, no longer lived during a time called the Late Pleistocene. Some animals, such as horses and camels, also disappeared from places like North America.

Modern humans evolved long ago, and during this time, many plants, insects, and mammals were common on land.