Carbon cycle

Carbon moves in a big circle.

Plants take carbon from the air. They use sunlight to turn it into food. This helps the plants grow big and strong.

Carbon also moves into the sea. The ocean holds a lot of carbon. It is the largest store of carbon near the surface.

Some carbon stays in the ground for a long time. It can be in rocks or deep in the soil. This can take millions of years.

People change how this circle works. We burn things like coal to make energy. This puts more carbon into the air.

This big circle helps our world stay healthy.

Carbon moves in a big circle around our world. This is called the carbon cycle. It is a set of steps that moves carbon between the air, the land, and the sea.

There are two main ways this cycle works. The fast cycle happens in just a few years. Plants take carbon dioxide from the air to make food. This is called photosynthesis.

The slow cycle takes millions of years. It moves carbon through rocks and deep inside the Earth. Most carbon is stored in rocks like limestone.

The ocean is a very big store for carbon. It holds much more carbon than the air does. Carbon enters the water from the air and from rivers. This can change the chemistry of the sea. This change is called ocean acidification.

Humans have changed this cycle. We mine and burn fossil fuels like coal and oil. This lets out a lot of extra carbon. This has caused the amount of carbon in the air to rise. This leads to global warming.

Carbon is a key part of life on Earth. It is found in all living things and many types of rocks. The carbon cycle is the way carbon moves and is reused throughout our world. This cycle includes the air, the land, the ocean, and even deep inside the Earth. It helps keep our planet in balance so life can continue to grow. Without this movement, the Earth would not be able to support us.

There are two different ways the carbon cycle works. The fast cycle, or biological cycle, moves carbon in just a few years. Plants use a process called photosynthesis to take carbon dioxide from the air. They turn it into organic carbon to grow. When plants or animals die, that carbon can return to the air or stay in the soil. The slow cycle is much longer and can take millions of years. It moves carbon through the Earth's crust between rocks, soil, and the ocean.

Scientists have studied these movements for a long time. Antoine Lavoisier and Joseph Priestley were the first to describe the carbon cycle. Later, Humphry Davy helped make these ideas popular. Today, we know that carbon is stored in many different places called reservoirs. The largest active pool of carbon is found in the ocean near the surface. The deep ocean holds even more carbon than the atmosphere.

Carbon moves between these stores through many different paths. In the atmosphere, carbon exists mostly as carbon dioxide and methane. Both of these gases can trap heat, which is part of the greenhouse effect. The ocean absorbs carbon dioxide from the air and from rivers. When too much carbon dioxide enters the water, it can cause ocean acidification. This means the ocean's pH value changes and its chemistry is altered.

Humans have changed the way the carbon cycle works. For hundreds of years, people have changed how land is used. We also mine and burn fossil fuels like coal, oil, and gas. These fuels are made of ancient organic remains. By burning them, we release extra carbon into the air. In 2020, carbon dioxide in the atmosphere had increased nearly 52% from pre-industrial levels. This extra carbon is one reason for global warming.

The carbon cycle is a complex system of movement and storage. It describes how carbon is recycled and reused throughout Earth's various systems. This cycle is a vital biogeochemical process. It moves carbon between the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere. Without this constant recycling, Earth could not sustain life.

Scientists divide the carbon cycle into two distinct speeds. The fast carbon cycle, or biological carbon cycle, moves carbon within a few years. This involves moving substances from the atmosphere to the biosphere and back. The slow carbon cycle, also called the deep carbon cycle, takes millions of years. It moves carbon through the Earth's crust between rocks, soil, the ocean, and the atmosphere.

The atmosphere contains carbon in two main forms: carbon dioxide and methane. Both gases are part of the greenhouse effect because they absorb and retain heat. While methane produces a larger greenhouse effect per volume, carbon dioxide is more significant. This is because carbon dioxide exists in much higher concentrations. Carbon dioxide is removed from the air primarily through photosynthesis. It also dissolves directly into bodies of water like oceans and lakes.

When carbon dioxide dissolves in water, it reacts to form carbonic acid. This process contributes to ocean acidification, which changes marine chemistry. The ocean is a massive carbon reservoir. The surface layer exchanges carbon rapidly with the atmosphere to maintain equilibrium. However, the deep ocean contains the largest active pool of carbon near the surface. It holds 50 times more carbon than the atmosphere. This deep layer exchanges carbon through thermohaline circulation, a process that takes hundreds of years.

The terrestrial biosphere stores carbon in living organisms and the soil. About 500 gigatons of carbon are stored in living plants and organisms. The soil holds approximately 1,500 gigatons of carbon. Autotrophs, such as plants, extract carbon dioxide from the air to create organic carbon. Heterotrophs receive carbon by consuming other organisms. Carbon leaves the land through respiration or combustion. It can also be washed into rivers or stay sequestered in the soil for thousands of years.

Most of Earth's carbon is stored in the lithosphere, or the Earth's crust. About 80% of this geological carbon is limestone and its derivatives. These form from the calcium carbonate in the shells of marine organisms. The other 20% is stored as kerogens. These form when terrestrial organisms are buried under high heat and pressure. Carbon can return to the atmosphere through volcanic activity. This happens when carbonate rocks are subducted into the mantle and undergo metamorphism.

Humans have significantly disturbed these natural cycles over the last few centuries. We modify land use and mine ancient organic remains like coal, petroleum, and gas. Burning these fossil fuels releases stored carbon into the atmosphere. By 2020, atmospheric carbon dioxide had increased nearly 52% over pre-industrial levels. This increase contributes to global warming and changes the ocean's pH. These human activities alter the balance that once kept carbon levels stable.

In the very distant future, the carbon cycle will change again. As the Sun ages, its increased luminosity will speed up surface weathering. This will likely push more carbon dioxide into the Earth's crust as carbonate. Scientists predict that in about 600 million years, carbon dioxide levels may fall too low for C3 photosynthesis. Eventually, the cycle may end entirely. If oceans evaporate in 1.1 billion years, plate tectonics may stop. Without volcanoes to pump out carbon, the cycle could cease between 1 and 2 billion years from now.