Quaternary

The Quaternary is the most recent period in Earth's history. It is part of the Cenozoic Era. This period began about 2.58 million years ago. It continues right up to the present day.

Scientists divide this time into two main parts called epochs. The first is the Pleistocene, which lasted from 2.6 million years ago until 12,000 years ago. The second is the Holocene, which began 12,000 years ago and is our current time. Some people suggested a third epoch called the Anthropocene. This would mark how humans changed the world starting with the Industrial Revolution. However, a governing body called the IUGS rejected that idea in 2024.

This period is defined by a way of working called the Quaternary glaciation. This means huge sheets of ice grew and melted in cycles. These cycles happen because of Milankovitch cycles. These cycles are changes in how much solar radiation, or sun energy, reaches Earth.

When the cycles change, the climate changes too. Huge glaciers moved far from the poles. They reached as far as 40 degrees latitude. These ice sheets covered much of North America and Europe. They also covered parts of Asia, South America, and Antarctica.

People have been studying these layers for a long time. In 1759, Giovanni Arduino suggested Earth's crust had four different orders. Later, in 1829, Jules Desnoyers used the term "quaternary" for sediments in France. He noticed these layers were younger than older rocks. In 1821, an engineer named Ignaz Venetz noticed signs of glaciers far from the Alps. A scientist named Louis Agassiz first doubted him. But Agassiz soon proved him right. Agassiz then created the Glacial Theory, which brought him great fame.

Many interesting things happened during these millions of years. The Bering Strait once closed to form a land bridge between Asia and North America. The English Channel also filled with land to connect Britain to Europe.

The Black Sea and Baltic Sea even became fresh water lakes. These changes happened when the straits of Bosphorus and Skagerrak emerged. During the Quaternary, recognizable humans began to exist. Modern humans evolved about 315,000 years ago. Mammals, insects, and flowering plants were the main living things on land.

We can see how this period shaped our world today. The Great Lakes in North America formed because of these ice ages. The Canadian Shield also readjusted, which affects places like Hudson Bay.

Many huge animals lived during the Pleistocene. These included mammoths, mastodons, and sabre-toothed cats. Sadly, many of these large mammals went extinct about 11,700 years ago. Even though the ice has mostly melted, the Quaternary is still happening. We are living through the very end of this amazing geological story.