The movement of water from the air to the Earth's surface and back forms which cycle?

• A. Carbon cycle
• B. Nitrogen cycle
• C. Hydrologic cycle
• D. Biogeochemical cycle

Answer: (C)

Water moving between the air and the Earth's surface in a continuous looping process is the hydrologic cycle. This cycle captures how water evaporates from oceans, rivers, and soil, rises into the atmosphere, cools and condenses into clouds, and then precipitates back to land and water bodies. Some of the water infiltrates the ground to refill aquifers, while some runs off into streams and rivers, eventually starting the cycle again. This cycle is driven largely by solar energy and is specific to water, unlike the other cycles that track elements like carbon or nitrogen. The broader term biogeochemical cycle includes multiple element cycles, but the description focusing on water moving through air and surface points squarely identifies the hydrologic cycle.