Learn how carbon moves in and on the surface of Earth, the forms it takes, and how it cycles to other parts of the planet.
Carbon takes many forms on land and moves between them in processes that last anywhere from seconds to millions of years. Learn more:
Decay:Carbon enters the soil when plant and animal matter decay. This decay process can also release some carbon to the atmosphere in the form of carbon dioxide and methane.
Consumption:Animals eat plants (and other animals) and use carbon from their food for energy and to grow new cells.
Manufacturing & Construction:Plant materials are used in construction and manufactured products.
Carbon cycles quickly (occurring on time scales of seconds to years)
Plants are called primary producers because they capture inorganic carbon in the atmosphere (carbon dioxide) and convert it to forms that can be used by other plants, animals, and humans.
Early in Earth’s history, plants on land and in the ocean filled the atmosphere with oxygen, which eventually allowed larger animals to evolve.
Carbon is in many materials on land and moves between them in processes that last anywhere from moments to millions of years. Learn more:
Carbon cycles slowly (occurring on time scales of hundreds to millions of years)
Photosynthesis:Plants use carbon dioxide from the ATMOSPHERE and energy from sunlight to make simple sugars, the building blocks of plant tissue.
There are between 3 and 30 million species
of animals on Earth, including humans.
Respiration:Animals exhale carbon dioxide as a waste product to the ATMOSPHERE.
All animals, including humans, contain carbon that originally came from other plants and animals.
Decay:Animals return carbon to the land when they poop or die and decompose.
Consumption:Animals consume carbon in the form of other plants and animals.
Manufacturing & Construction:Many rocks used in construction and manufacturing are the fossilized remains of long-dead animals.
Compaction:Under pressure and over long periods of time, soil on land and sediment on the seafloor form rocks.
Soil is made of organic material and tiny rock particles, and carbon is found in both.
Respiration:Carbon in soil provides food for microbes, which return carbon dioxide to the ATMOSPHERE.
Decay:Organic carbon in dead plants and animals and animal poop become part of the soil.
Runoff:Rain and melting snow running over land carries carbon into rivers and streams and eventually to the OCEAN.
It can take more than 500 years to form one inch of topsoil.
Carbon is most abundant in sedimentary rocks such as limestone and shale.
Geological processes:Natural processes such as rock weathering (physical and chemical breakdown of rocks) remove carbon dioxide from the ATMOSPHERE.
80% of carbon-containing rocks are the remains of shells and corals; the rest contain organic carbon from plants and other organisms.
Manufacturing and Construction:Some rocks and minerals that contain carbon are mined for use in building materials, such as concrete, or chemicals, such as plastics.
Energy production:Fossil fuels are the primary sources of energy worldwide. Burning fossil fuels releases carbon dioxide and fine particles to the ATMOSPHERE.
Cement production accounts for about 5% of human-produced carbon emissions.
Deforestation:Clear-cutting forests reduces the amount of carbon dioxide that can be removed from the atmosphere by photosynthesis and the plant material is often burned, which adds carbon back to the ATMOSPHERE.
Human activity is a large and growing part of the global carbon cycle.
Runoff:Human activities such as farming and logging can change the amount and rate at which carbon is carried from the land to the OCEAN via runoff.
Burial:Discarded waste in landfills releases methane (a potent greenhouse gas) into the ATMOSPHERE and slowly breaks down to become a part of the soil.
Manufacturing & construction:Some rocks and minerals that contain carbon are mined for use in building materials, such as concrete, or chemicals, such as plastics.
Carbon takes many forms in the ocean and moves between them in processes that last anywhere from seconds to millions of years. Learn more:
Exchange of carbon dioxide between the atmosphere and the ocean depends on the difference in concentration between the water and air, as well as temperature, wind speed, wave formation, and ocean circulation.
Absorption:Carbon dioxide in the ATMOSPHERE dissolves into the surface ocean.
There is 50 times as much carbon in the ocean as in the atmosphere.
Degassing:Dissolved carbon dioxide gas is also released to the ATMOSPHERE, especially in upwelling areas where deep, carbon-rich ocean water is brought to the surface.
Photosynthesis:Plants in the ocean use carbon dioxide from the ATMOSPHERE and energy from sunlight to make simple sugars, the building blocks of plant tissue.
Shell formation:Some phytoplankton use carbonate, an inorganic form of carbon found in seawater, to make their shells.
Microscopic plants in the ocean conduct half of the photosynthesis on Earth and form the base of the food chain, essentially supporting all marine life.
Export:Dead phytoplankton float through the water and become food for marine animals or eventually settle to the bottom of the ocean.
Plants link the earth’s inorganic and organic carbon cycles by capturing inorganic carbon dioxide gas and turning it into organic forms of carbon that other organisms can use.
Consumption:Many marine animals eat phytoplankton and other animals and use the carbon for energy and to grow new cells.
Respiration:Marine animals take oxygen out of the water and respire (breathe out) carbon dioxide to the ATMOSPHERE, much like humans and land animals.
Export:Detritus (dead animals and animal poop) float through the water and become food or eventually settle to the bottom of the ocean.
Carbon makes up nearly half the weight of dried animal tissue.
Consumption:Many marine animals eat phytoplankton and use the carbon it contains for energy and to grow new cells.
Shell formation:Some zooplankton (tiny marine animals) and corals use carbonate, an inorganic form of carbon found in seawater, to make their shells and skeletons.
The ocean contains the biggest and the smallest creatures on Earth: the blue whale is about 30 meters (100 feet) long and some microbes are 1 micrometer (0.001mm).
Detritus is food for many organisms, particularly in the deep ocean where food is scarce.
Settling:Detritus in the water that is not consumed by microbes or other organisms settles to the seafloor.
Detritus contains mostly organic material and some inorganic shells of dead animals.
Consumption:Microbes eat detritus and convert the organic carbon into carbon dioxide and dissolved carbon that marine plants use for photosynthesis.
The deep ocean is a major long-term reservoir of the Earth’s carbon.
Accumulation:Detritus that settles to the seafloor is either consumed by microbes or buried in sediment layers that, over long periods, can preserve a record of past conditions on Earth.
Compaction:Over time, carbon-rich sediments on the ocean floor compact under pressure to form sedimentary rocks such as limestone and shale.
The deepest place in the ocean is one mile
deeper than Mount
Everest is tall.
The ocean has absorbed roughly half of all human carbon dioxide emissions.
Fishing:More than 130 million tons of fish are removed from the world’s oceans each year; an additional 7 to 27 million tons of marine life are considered "bycatch" and discarded each year.
Ocean acidification:By burning fossil fuels, humans release carbon dioxide to the ATMOSPHERE, some of which dissolves in seawater and lowers its pH, which disrupts many of the plants and animals that live there.
Humans impact the ocean carbon cycle through activities such as energy production, fishing, and agriculture.
Blooms:Human activity on LAND, particularly farming, causes nitrogen and other nutrients to run off into the ocean, causing blooms of algae and marine plants.
Carbon takes many forms in the deep earth and moves among them in natural processes last anywhere from seconds to millions of years. Learn more:
Volcanic activity:Carbon from deep beneath Earth's surface is released to the ocean and ATMOSPHERE via hydrothermal vents and volcanoes.
The mantle is the layer of Earth’s interior between the crust and the outer core.
Tectonic processes can actually bring oceanic crust and mantle material up to the land surface, forming geologic features known as ophiolites.
Subduction:Carbon is transported from the OCEAN to the deep earth in subduction zones, places where two of Earth’s tectonic plates collide and one plunges beneath the other into the mantle, where it can be locked away for long periods of time.
Mining:Many manmade materials contain carbon that once resided deep beneath the surface of the Earth and are brought to the surface by mining. Mining often changes the landscape in ways that affect how carbon is cycled to the atmosphere and OCEAN.
Human activity is moving carbon out of the deep earth much faster than at any time in Earth's history.
The carbon released in one day from burning fossil fuels equals the amount of carbon captured
in one year by all plants on
land and in the ocean.
Fossil fuels:Fossil fuels are hydrocarbon deposits (coal, oil, natural gas) formed over millions of years by the decay and compression of ancient plants and animals. Fossil fuels are the primary sources of energy worldwide and, when burned, release large amounts of carbon dioxide to the ATMOSPHERE.
Manufacturing & Construction:Fossil fuels and carbon-containing minerals used on LAND are an important part of many manufactured products and construction materials.
Carbon takes many forms in Earth's atmosphere and last anywhere from seconds to millions of years around the planet. Learn more:
Methane is more than 20 times as effective as carbon dioxide at trapping heat, but the atmosphere contains less methane than carbon dioxide, and methane does not stay in the atmosphere as long as carbon dioxide.
Biological activity:Bacteria in oxygen-free environments such as OCEAN sediments, marshes, rice paddies, and the digestive systems of cattle on land generate methane. Other bacteria in oxygen-rich environments can eat methane.
Earth processes:Hydrothermal vents in the
DEEP EARTH and methane clathrates, ice-like structures under the seafloor, occasionally release large amounts of methane into the ocean.
Natural breakdown:Most atmospheric methane reacts with other chemicals and sunlight in the atmosphere to break down.
Human activity:Methane is a major component of fossil fuels burned on LAND such as natural gas. Excess methane from fossil fuel is sometimes burned as it is vented to the atmosphere.
Methane produced by cow and sheep digestion contributes up to 19% of Earth’s methane emissions each year.
Natural breakdown:CFCs degrade very slowly in the upper atmosphere, where they react with ozone and sunlight and break into smaller molecules.
Human activity:CFCs have been used on LAND as refrigerant, propellants, fire-fighting chemicals, and solvents, and have no natural source.
The atmosphere contains a miniscule amount of various CFCs, but they have a very long life (100 years or more) and are very effective at trapping the sun's heat.
CFCs were banned in 1989 by the Montreal Protocol because of the damage they can do to Earth's ozone layer. They were replaced by new chemicals, some of which are even stronger greenhouse gases.
Natural processes:Many carbon-containing particles are released by the land, DEEP EARTH, and ocean via volcanic eruptions, fires, dust storms, plants, and sea spray.
Human activity:Coal, wood, oil and gas burning on LAND account for 10% of all particles in the atmosphere.
For two years after the 1991 eruption of Mt. Pinatubo, the surface temperature on Earth was measurably cooler because aerosols in the atmosphere reflected
some sunlight back into space.
Aerosols are tiny particles in the atmosphere that often contain carbon.
Settling:Large and small particles either break down in the atmosphere by reacting with solar radiation or settle onto the land and OCEAN surface.
Photosynthesis:Some CO2 leaves the atmosphere when plants on LAND and in the ocean use it to make plant material and energy.
Human activity:An increasing amount of atmospheric CO2 comes from human activities on LAND such as deforestation and fossil fuel burning.
Earth processes:Natural processes such as volcanic eruptions on land and in the ocean
add CO2 from the DEEP EARTH to the atmosphere, whereas rock weathering removes CO2 from the atmosphere.
Scientists have been monitoring atmospheric CO2 concentrations since the 1950s and have seen a steady increase in this greenhouse gas due to human activities.
Respiration:Animals on land and in the OCEAN exhale CO2 as a waste product into the atmosphere.
CARBON DIOXIDE (CO2)
Absorption & degassing:Carbon dioxide gas is exchanged between the atmosphere and the ocean by dissolving into the ocean and degassing out of the ocean.
CO2 makes up less than 0.1% of Earth's atmosphere, but it is critical to life on Earth. It is also a greenhouse gas that traps the sun's heat, so the continued increase of atmospheric CO2 is cause for concern.