Which biogeochemical cycle is defined as slowest and non-gaseous?

Which biogeochemical cycle is defined as slowest and non-gaseous?

• A. Phosphorus cycle
• B. Carbon cycle
• C. Oxygen cycle
• D. Nitrogen cycle

Answer: (A)

Think about how fast a cycle moves and whether a gas is involved. The fastest cycles involve gases that shuttle between the atmosphere and living things, like carbon dioxide and oxygen, or nitrogen with its gaseous N2 form. Phosphorus, by contrast, does not have a gas phase under normal conditions. It moves mainly through rocks, soils, water, and organisms as phosphate, getting released by weathering, taken up by plants, recycled by decomposition, and finally buried in sediments. These steps—weathering, uptake, decomposition, sedimentation—operate on geological timescales, so the phosphorus cycle progresses very slowly. Because it remains mostly in solid phases and sediments rather than in the air, it’s the slowest and non-gaseous cycle.

Think about how fast a cycle moves and whether a gas is involved. The fastest cycles involve gases that shuttle between the atmosphere and living things, like carbon dioxide and oxygen, or nitrogen with its gaseous N2 form. Phosphorus, by contrast, does not have a gas phase under normal conditions. It moves mainly through rocks, soils, water, and organisms as phosphate, getting released by weathering, taken up by plants, recycled by decomposition, and finally buried in sediments. These steps—weathering, uptake, decomposition, sedimentation—operate on geological timescales, so the phosphorus cycle progresses very slowly. Because it remains mostly in solid phases and sediments rather than in the air, it’s the slowest and non-gaseous cycle.