What Is The Carbon Cycle?

A pictorial representation of the carbon cycle.


Carbon is an essential natural element for the earth. It is contained in some of the most important organic compounds, such as carbon dioxide (CO2), fossil fuels, and proteins. The carbon atom in the atmosphere is also responsible for keeping the earth warm and habitable.

Just like water, carbon flows through the earth in a continuous loop called the carbon cycle. The presence of carbon is managed by the carbon cycle, which in the long term keeps the ice age at bay.

What Is The Carbon Cycle?

Four places store carbon on earth: living organisms, rocks, water, and the atmosphere. The amount of carbon in this cycle is constant, but the amount of carbon in each place changes constantly.

There are two types of carbon cycle, the slow cycle, and the fast cycle. In the fast cycle, the carbon moves between living organisms and the atmosphere. The slow cycle involves the exchange of carbon in the atmosphere and the lithosphere (the layers of rocks beneath the surface of the earth).

Fast Cycle

In the fast cycle, carbon enters the food chain through its lowest tier, the autotrophs such as trees or algae that use CO2 in the atmosphere to produce their own nutrients and oxygen. They release the oxygen into the atmosphere and keep the nutrients as an energy reserve.

The carbon kept by autotrophs as an energy reserve is distributed through the food chain to other living organisms. This carbon stays in the food chain until released through breathing or decomposition.

Humans and animals need to breathe using oxygen (O2), which bonds with carbon through respiration to produce CO2, which will then be returned to the atmosphere. In decomposition, bacteria break down material from other living organisms and releases CO2 to the atmosphere.

Slow Cycle

The slow cycle takes place mostly in the lithosphere. Carbon takes up millions of years to move through this cycle. This cycle starts with the atmosphere, where most carbon is found in the form of carbon dioxide. There are multiple ways for the carbon to enter the lithosphere.

The first one is through weathering rocks. Rainwater saturated with carbon dioxide produces a weak acid. This acid rain falls onto the surface of the earth, gradually dissolving rocks. Weathered rocks release minerals, such as calcium, and produce inorganic carbon.

Carbon can also dissolve in the ocean, this chemical reaction will produce bicarbonate ions. The dissolved carbon will bond with calcium available in the ocean to produce calcium bicarbonate, a key material for building shells for some creatures.

When the marine organism dies, it sinks to the floor of the ocean. Over time, it will harden and merge with the floor to join the lithosphere.

On land, decomposition supported by mud and heat will also help trap the carbon in the lithosphere.

Sometimes, anaerobic (oxygen-free) decomposition happens to organisms that pile up before it’s decomposed perfectly. This decomposition will produce fuel, oil, and others, most of which will be burned by humans for its energy and release the carbon back to the atmosphere.

The natural way to release carbon back to the atmosphere is through tectonic plate movements beneath the sea or volcanic activity. The friction of the tectonic plates causes extreme heat and pressure, causing the plate to melt and release carbon dioxide. Volcanic eruptions release gases into the air, including carbon dioxide.


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