Where is the Earth's carbon stored?

By: Jamie Page Deaton  | 
Do you know where the Earth's carbon is stored?
Ryan McVay/Getty Images

No one would blame you if you're sick of hearing about carbon. Every day it seems there are news stories about rising carbon levels, carbon emissions, and even the search for new carbon-based life forms. It's enough to leave anyone wondering just what the heck carbon is and where the Earth is keeping all of it.

Carbon is a chemical element, and a pretty common one. It's the sixth most common element in the universe and the 15th most common one in the Earth's crust. Unlike a lot of other chemical elements, you can actually see some forms of carbon. Diamonds are one form of carbon, as is the graphite in the pencil you used in chemistry class when learning this stuff the first time around.


However, the Earth isn't storing most of its carbon in diamonds and pencils. Rather, amorphous carbon is a third form of carbon, and it's a lot harder to see since it doesn't have a crystalline structure. Where are these carbon atoms? The answer lies in the carbon cycle steps.

Carbon Compounds and Atmospheric Carbon

So, where is all this carbon hiding out? Look in the mirror. Carbon is the building block for all life on Earth, which is why Captain Kirk and NASA are always looking for carbon-based life forms on other planets. Carbon compounds (or organic compounds, as they're also called) represent a good chunk of the total amount on Earth and can be found in living and dead organic molecules. That means it's not only in you and your dog, but also in things like fossil fuels and road kill.

Carbon moves through the atmosphere as carbon dioxide, which can be found in burning fossil fuels and the breath of living organisms. It's in the organic matter of soil, rocks, and water. Especially water, but we'll get to that soon enough.


How a Natural Carbon Cycle Begins

The elemental infrastructure known as the carbon cycle ensures that everywhere on Earth gets a balanced distribution of this precious commodity. And the first stop in the natural carbon cycle is photosynthesis. Plants and algae use the energy of the sun to convert atmospheric carbon into glucose. Thus, the food chain on Earth is born!

With a sudden influx of glucose comes animals (including us humans), who eat photosynthetic organisms as well as the carbon stored within them. As this food is digested, the glucose is then oxidized through respiration, which returns carbon dioxide back to the atmosphere. The food chain continues even when animals and humans die, as their decompositions release energy and more carbon.


Carbon Sinks in Our Oceans

Without question, the most carbon on Earth is stored in a surprising place: the ocean. There's estimated to be 38,000 to 40,000 billion metric tons of carbon in the ocean itself with a whopping 66 million to 100 million-billion metric tons of carbon in marine sediments and sedimentary rocks.

Those sediments and rocks develop from the hard shells and body parts of organisms, since marine animals convert carbon as well. When they die, their bodies sink to the ocean floor, and the hard parts break down into sediment, which is later formed into sedimentary rocks. This is an example of carbon sequestration; forests and oceans are prime "carbon sinks", safekeeping huge amounts of carbon molecules.


Fossil Fuels and Excess Carbon Dioxide Gas

So how do these dormant carbon compounds get back into the cycle? A volcanic eruption, no less! Movements in the Earth's crust lead to volcanic activity which disperses wild amounts of carbon dioxide back into the atmosphere.

While natural processes play their role, human activities are complicating the carbon cycle diagram. By burning fossil fuels and creating greenhouse gases, humans are contributing to global warming and ocean acidification. Climate change affects the carbon cycles at every stage, reducing the ability of organisms to absorb carbon dioxide and amplifying the release of greenhouse gas.


Why is the Carbon Cycle Important?

Carbon compounds regulate Earth's atmosphere, which all living organisms are dependent on. It also provides humanity with an environmental stability we take for granted. If Earth's temperature continues to rise, the carbon cycle will be irrevocably damaged, leading to more greenhouse gases.

From the skies up above to the bottom of the ocean floor, carbon cycles keep plants and animals in a sustainable pattern. So, the next time you wonder where the Earth's carbon is, take a long look in the mirror, and then put on your bathing suit, and hit the beach. You'll see carbon cycling, and all of these chemical reactions, hard at work!