Volcanic eruptions significantly influence the carbon cycle by releasing substantial amounts of carbon dioxide into the atmosphere.

Volcanoes are integral components of the carbon cycle, a dynamic process that circulates carbon among the Earth’s lithosphere, atmosphere, hydrosphere, and biosphere. During an eruption, a volcano emits various gases, notably carbon dioxide ($\text{CO}_2$). This emission contributes to the overall functioning of the carbon cycle.

The carbon cycle is a complex system wherein carbon compounds traverse the Earth’s different compartments. This cycle includes the absorption of carbon dioxide by plants through photosynthesis, the release of carbon dioxide via respiration and decay, and the storage of carbon within the Earth’s crust and oceans. Volcanic eruptions introduce an additional element to this cycle by releasing carbon that has been stored in the Earth’s interior back into the atmosphere.

The carbon dioxide released during volcanic eruptions primarily originates from the Earth’s mantle, where it has been sequestered for millions of years. This carbon is liberated when intense heat and pressure within the Earth cause rocks to melt, generating magma. As the magma ascends toward the surface, the pressure diminishes, allowing the dissolved gases to escape. When a volcano erupts, these gases—including carbon dioxide—are expelled into the atmosphere.

Although the amount of carbon dioxide emitted by volcanoes is relatively minor when compared to human activities, such as burning fossil fuels, large volcanic eruptions can still exert a substantial influence on the carbon cycle. For instance, the eruption of Mount Pinatubo in the Philippines in 1991 released an estimated $42$ million tonnes of carbon dioxide into the atmosphere, which is approximately $0.05\%$ of the global carbon emissions for that year.

In addition to carbon dioxide emissions, volcanic eruptions can affect the carbon cycle in other significant ways. The ash and dust expelled during an eruption can obstruct sunlight, thereby reducing the extent of photosynthesis. This reduction can lead to a temporary decline in the amount of carbon dioxide absorbed by plants, further elevating the concentration of this gas in the atmosphere.

In summary, while volcanic eruptions are not the primary drivers of changes within the carbon cycle, they do contribute to this intricate system. Understanding their impact is crucial for studying the Earth’s climate and atmospheric composition.