CO₂ dissolves in seawater to form carbonic acid (H₂CO₃), which dissociates into H⁺ and HCO₃⁻. Increased H⁺ concentration lowers the pH of the ocean, causing ocean acidification. This process reduces carbonate ion concentration, affecting marine organisms with calcium carbonate shells.

Igneous rocks are formed from cooling magma. Weathering and erosion produce sediments which compact into sedimentary rocks. Heat and pressure transform sedimentary or igneous rocks into metamorphic rocks. Melting of any rock type produces magma, completing the cycle.

Methane (CH₄) and nitrous oxide (N₂O). These gases absorb infrared radiation emitted from Earth’s surface and re-radiate it back to the atmosphere, trapping heat and enhancing the greenhouse effect, leading to global temperature rise.

Limestone (CaCO₃) acts as a carbon sink. Marine organisms form shells from calcium carbonate which accumulate on the ocean floor and eventually form limestone, locking carbon away for millions of years.

The ozone layer absorbs harmful ultraviolet (UV) radiation from the sun. Without it, increased UV exposure would damage DNA, leading to higher rates of skin cancer and mutations in living organisms.