Question

what is the primary impact of combustion of fossil fuels on the carbon cycle?
it releases vast amounts of co2 into the atmosphere

Explanation:

Fossil fuels like coal, oil, and gas contain carbon. When burned (combustion), they react with oxygen. The chemical reaction \( \text{C} + \text{O}_2
ightarrow\text{CO}_2 \) (for pure carbon, simplified from complex fossil - fuel combustion) releases \( \text{CO}_2 \) into the atmosphere. This \( \text{CO}_2 \) was sequestered (stored) in the Earth's crust as fossil fuels for millions of years. In the carbon cycle, this sudden release disrupts the balance. Natural processes like photosynthesis and ocean absorption can only absorb \( \text{CO}_2 \) at a certain rate. So, combustion of fossil fuels is a major anthropogenic (human - caused) source of \( \text{CO}_2 \) emissions to the atmosphere.

Answer:

It releases vast amounts of \( \text{CO}_2 \) into the atmosphere.