Eocene

A long time ago, the Earth was very hot.

There was no ice at the poles. The land and seas were different. Many plants and animals lived then.

Warm air and water moved around the world. This kept the planet very warm.

The land also moved slowly. Large pieces of land drifted to new spots.

Later, the world began to cool down. Ice started to grow at the poles. This changed the world once more. It was a very busy time for our Earth.

The Eocene was a long time in Earth's history. It lasted from 56 to 33.9 million years ago.

This time was part of the Cenozoic Era. It was a period of big changes for our planet.

At first, the Earth was very warm. This is often called a greenhouse state. There was almost no ice at the poles.

Because it was so warm, sea levels were very high. They were 150 meters higher than they are today. Gases like carbon dioxide and methane helped keep the heat in. Methane is a gas that traps heat very well. Much of it came from swamps and forests.

During this time, the continents moved. Australia and Antarctica were still joined together. This helped move warm water around the world. Later, Australia split away. This allowed cold water to flow around Antarctica.

As the world cooled, ice began to grow at the poles. The Eocene ended with a big event called the Grande Coupure. This event caused many species to die out.

The Eocene was a very important time for our planet. It was a geological epoch that lasted from 56 to 33.9 million years ago.

This era is part of the Cenozoic Era. Scientists call it a time of big changes. The world moved from a hot "house" to a cold "house" climate. This means the Earth went from being very warm to being much cooler. It was a time when modern life began to take shape.

At the start, the Earth was incredibly hot. This began with the Paleocene-Eocene Thermal Maximum. During this time, a lot of carbon was released into the air and oceans. This caused intense warming and made the oceans more acidic. Because it was so warm, there was almost no ice at the poles.

The sea levels were much higher than they are today. In fact, the sea was 150 meters higher than it is now. Gases like methane and carbon dioxide helped trap the heat. Methane is a gas that is very good at trapping warmth.

As the Eocene went on, the continents moved to new places. At first, Australia and Antarctica were still connected. This connection helped warm water travel around the globe. This kept the whole planet very warm. Later, around 45 million years ago, Australia split away.

This change created a cold water path near Antarctica. As the world cooled, ice began to grow at the poles. The ocean around Antarctica started to freeze. This helped the cooling process continue.

Many smart people helped us understand this time. A Scottish geologist named Charles Lyell studied these periods in 1833. Later, John Phillips proposed the name Cenozoic in 1840. In 1853, Moritz Hörnes introduced the name Paleogene. Scientists use special fossils to mark the dates. They look at tiny sea creatures called foraminifera. When these tiny creatures disappeared, it helped mark the end of the Eocene. This end is also called the Grande Coupure, or the "Great Break."

We can see how the Eocene connects to our world today. The way the continents moved then shaped our maps now. For example, India crashed into Asia to form the huge Himalayas. The Eocene also had many different stages. These include the Early, Middle, and Late Eocene.

We can study the rocks left behind to learn about these times. These rocks tell the story of how our Earth changed. It shows us how much our climate can shift over millions of years.

The Eocene is a significant geological epoch within the Paleogene Period of the Cenozoic Era. It lasted from approximately 56 million years ago (Ma) to 33.9 Ma. The name comes from Ancient Greek words meaning the "dawn of recent life."

This epoch is vital for understanding Earth's history. It represents a massive climatic transition. The planet shifted from a "hot house" state to a "cold house" state. This period saw the rise of modern biological systems.

The Eocene began with the Paleocene-Eocene Thermal Maximum (PETM). This was a short period of intense global warming. It occurred around 55.8 Ma due to a massive release of carbon. This carbon entered the atmosphere and ocean systems. The sudden change caused ocean acidification. It also triggered a major mass extinction. Between 30% and 50% of benthic foraminifera died out. These are single-celled organisms used as bioindicators of marine health.

Climate patterns during the Eocene were highly dynamic. The Early Eocene was characterized by extreme warmth. This reached a peak during the Eocene Optimum around 49 Ma. During this time, there was little to no polar ice. Consequently, sea levels were about 150 meters higher than today. The middle Eocene saw a cooling trend starting around 47.8 Ma. This was briefly interrupted by the Middle Eocene Climatic Optimum (MECO). The MECO lasted about 400,000 years. It caused a 4° to 6°C warming in both surface and deep oceans.

Greenhouse gases were the primary drivers of these temperature shifts. Carbon dioxide and methane played massive roles. During the early Eocene, carbon dioxide levels were very high. Some proxies suggest levels of 700–900 ppm. Other models suggest concentrations as high as 1,680 ppm. For comparison, modern levels are around 400 ppm. Methane also had a drastic effect. Methane has a global warming potential 29.8 times higher than carbon dioxide over 100 years. Much of this methane came from expanding wetlands and forests.

Plate tectonics reshaped the world during this epoch. At the start, Australia and Antarctica were still connected. This connection allowed warm equatorial currents to circulate. These currents helped maintain high global temperatures. Around 45 Ma, Australia split from Antarctica. This created a cold water channel. This isolation likely contributed to the cooling of the Antarctic region. In the north, the supercontinent Laurasia began to fragment. Europe, Greenland, and North America drifted apart.

Significant geological events also occurred across different continents. In Asia, India collided with the Asian continent. This collision began the formation of the Himalayas. Around 35 Ma, an asteroid impact occurred near North America. This created the Chesapeake Bay impact crater. In western North America, the Kishenehn Basin was uplifted. This uplift led to the formation of huge lakes. These lakes deposited the Green River Formation lagerstätte. This is a famous site of well-preserved fossils.

Geologists divide the Eocene into three distinct subdivisions. These are the early, middle, and late Eocene. They correspond to specific rock layers called the lower, middle, and upper Eocene. The early Eocene includes the Ypresian Stage. The middle Eocene includes the Lutetian and Bartonian stages. The late Eocene is defined by the Priabonian Stage.

Scientists use these stages to organize the complex history of the period.

Our understanding of the Eocene comes from many researchers. In 1833, Charles Lyell divided the Tertiary Epoch. In 1840, John Phillips proposed the Cenozoic name. In 1853, Moritz Hörnes introduced the Paleogene term. Today, the International Commission on Stratigraphy standardizes these boundaries. The end of the Eocene is marked by the Eocene–Oligocene extinction event. This is also called the Grande Coupure, or the "Great Break." This event is linked to the disappearance of Hantkeninidae foraminifera. It also may be related to bolide impacts in Siberia and Chesapeake Bay.