Calcium cycle

The calcium cycle is the movement of calcium among rocks, soil, water, organisms, and sediments through geological, chemical, and biological processes. It links mineral weathering and sediment formation with calcium uptake and release by living things.

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Chemical weathering: The breakdown or alteration of rocks and minerals through chemical reactions with water, gases, or dissolved substances. Dissolution releases calcium from minerals into soil and surface waters.
Calcium: A chemical element with atomic number 20, common in minerals and essential to many biological processes. Its ions and mineral compounds are the forms exchanged throughout the cycle.
Plant nutrition: The acquisition and use of mineral nutrients required for plant growth and function. Plants absorb calcium from soil and return it through litter and decomposition.
Carbonate sedimentation: The accumulation of calcium-carbonate particles and precipitates in marine or freshwater sediments. It removes calcium from water and stores it in deposits that may become rock.
Carbonate dissolution: The reaction in which carbonate minerals dissolve in water, commonly aided by dissolved carbon dioxide. It mobilizes calcium from limestone and other carbonate rocks.
Calcite: A crystalline mineral composed of calcium carbonate and the most stable common form of calcium carbonate at Earth’s surface. It is a major calcium reservoir in limestone and marine sediments.
Ocean acidification: The decline in ocean pH caused mainly by seawater absorbing carbon dioxide from the atmosphere. Lower carbonate availability can hinder calcium-carbonate formation and increase shell dissolution.
Limestone: A sedimentary rock composed chiefly of calcium carbonate, commonly formed from shells or carbonate precipitates. It is a large calcium store that can return calcium through weathering.
Calcium carbonate: A chemical compound found in minerals such as calcite and aragonite and in many shells and skeletons. Its precipitation and dissolution transfer calcium between water, sediments, and organisms.
Aragonite: A crystalline form of calcium carbonate that is less stable at Earth’s surface than calcite. Many marine organisms build aragonite structures that can later dissolve or become sediment.