Quaternary

We live in a special time.

This time is called the Quaternary. It started 2.58 million years ago. It is still happening today.

During this time, huge sheets of ice grew and melted. This happened many times. The ice changed the land and the water.

Big animals lived back then, too. Some were mammoths. Others were cats with long teeth. Many of these animals are gone now.

Humans have lived on Earth during this time. We are part of this amazing story.

We live in a time called the Quaternary. This period started 2.58 million years ago. It is the most recent time in Earth's history.

This time is known for ice. Huge sheets of ice grew and melted many times. These are called glaciations. This happened because of Milankovitch cycles. These cycles are changes in how much sun reaches Earth. The ice moved far from the poles. It covered much of North America and Europe. It also covered parts of Asia and South America.

These ice ages changed the world. They made land bridges between places. One bridge linked Asia and North America. Another linked Britain to Europe. The ice also changed the seas. The Black Sea and Baltic Sea became fresh water lakes.

Many big animals lived during this time. We call them megafauna. This includes mammoths and sabre-toothed cats. Many of these animals died out long ago. Modern humans also appeared during this time. We evolved about 315,000 years ago. The Quaternary is still happening right now.

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.

The Quaternary is the most recent geologic period in Earth's history. It is the final period of the Cenozoic Era and the Phanerozoic eon. This period began approximately 2.58 million years ago. It continues through the present day. Scientists study the Quaternary to understand recent climate changes and biological shifts. It follows the Neogene Period in the geologic time scale. This period is essential for understanding the world we inhabit today.

The Quaternary is defined by the Quaternary glaciation. This process involves the cyclic growth and decay of massive continental ice sheets. These cycles are driven by Milankovitch cycles. These cycles are variations in the amount of solar radiation reaching Earth. As solar energy changes, the global climate shifts. These shifts cause glaciers to advance or retreat across continents. This mechanism has shaped the physical geography of our planet for millions of years.

Geologists divide the Quaternary into two distinct epochs. The first is the Pleistocene, which began 2.6 million years ago. It lasted until about 12,000 years ago. The second is the Holocene, which began 12,000 years ago and continues today. Some scientists proposed a third epoch called the Anthropocene. This would mark the impact of humans on the environment since the Industrial Revolution. However, the International Union of Geological Sciences rejected this in 2024.

Our understanding of this period grew through many scientific discoveries. In 1759, Giovanni Arduino suggested Earth's crust had four successive orders. In 1829, Jules Desnoyers used the term "quaternary" to describe sediments in France. He noticed these layers were younger than Tertiary rocks. Later, Ignaz Venetz suggested glaciers once existed far from the Alps. Louis Agassiz initially doubted this but eventually proved it was true. Agassiz's Glacial Theory gained him international fame and changed geology forever.

The Quaternary has seen massive changes in geography and sea levels. During glacial epochs, the emergence of the Bosphorus and Skagerrak straits occurred. This turned the Black Sea and Baltic Sea into fresh water lakes. Rising sea levels later flooded them back into salt water. Land bridges also appeared during this time. The English Channel filled to connect Britain to mainland Europe. The Bering Strait closed to connect Asia and North America. These shifts allowed animals and plants to move between continents.

Biological life has also undergone dramatic changes during this period. The Late Pleistocene saw a major extinction of large mammals. Famous creatures like mammoths, mastodons, and sabre-toothed cats disappeared. In North America, horses, camels, and American cheetahs also went extinct. Modern humans evolved roughly 315,000 years ago. During much of the Quaternary, mammals, flowering plants, and insects dominated the land. The end of the glacial period about 11,700 years ago changed many habitats.

The Quaternary is closely linked to the physical structure of the Earth. While plate tectonics moved continents, there was relatively little change in their distribution. However, the weight of ice caused the Canadian Shield to readjust. This movement influenced the current shapes of Hudson Bay and the Great Lakes. The Quaternary geological record is preserved in much greater detail than older periods. This allows scientists to trace specific events, like the flash flooding of the American Northwest Scablands. Studying this period helps us connect past climate cycles to our current environment.