9.1.4 How Carbon Dioxide Decreased

Algae and plants play a significant role in reducing the percentage of carbon dioxide in the Earth's atmosphere through the process of photosynthesisThe process by which plants use light energy to produce glucose.. During photosynthesis, carbon dioxide is absorbed by plants and algae, and through a series of chemical reactions, it is converted into glucose (a type of sugar) and oxygen.

As plants and algae carry out photosynthesis, they remove carbon dioxide from the atmosphere, utilising it as a source of carbon to build their organic molecules. This process helps to regulate the levels of carbon dioxide in the atmosphere.

However, the decrease in atmospheric carbon dioxide is not solely due to photosynthesis. Another significant factor is the formation of sedimentary rocks and the creation of fossil fuels. Over millions of years, as dead organic matter, including plants and marine organisms, accumulated on the Earth's surface, layers of sediment formed.

Through a process known as diagenesisThe physical and chemical changes that occur in bone or teeth after burial, often altering isotope values., these layers of sediment gradually transformed into sedimentary rocks, such as limestone. Limestone formation involves the sequestration of carbon dioxide from the atmosphere. Carbon dioxide dissolved in water combines with calcium ions to form calcium carbonate, the primary component of limestone.

Additionally, some of the organic matter that gets buried in sediment can undergo fossilisation, leading to the formation of fossil fuels such as coal, oil, and natural gas. Fossil fuels contain stored carbon that was originally removed from the atmosphere through photosynthesis millions of years ago.

The deposition of carbon in sedimentary rocks and the formation of fossil fuels effectively lock away carbon dioxide from the atmosphere for long periods of time. This natural process acts as a carbon sink, contributing to the decrease in atmospheric carbon dioxide levels over geological timescales.

Conclusion

The decrease in atmospheric carbon dioxide is influenced by the photosynthetic activities of plants and algae, as well as the formation of sedimentary rocks and the accumulationChange in a physical quantity over time, whether that be an increase, decrease, or no change at all. of fossil fuels. These processes work together to regulate the carbon dioxide levels in the atmosphere, balancing the carbon cycle on Earth.