Biogeochemical Cycles and Key Environmental Processes

Biogeochemical cycle

A natural pathway by which essential elements of living matter are circulated in the environment.

Hydrologic cycle

The continuous movement of water on, above, and below the surface of the Earth, involving processes such as evaporation, condensation, and precipitation.

Eutrophication

The process by which a body of water becomes overly enriched with nutrients, leading to excessive growth of algae and depletion of oxygen.

Limiting nutrient

A nutrient that is in short supply and limits the growth of organisms in an ecosystem.

Nitrogen fixation

The process of converting atmospheric nitrogen (N2) into a form that plants can absorb and use, typically ammonia (NH3).

Decomposition

The process by which organic substances are broken down into simpler organic or inorganic matter, often by microorganisms.

Runoff

The flow of water, from rain or melting snow, that moves across the land surface and eventually enters rivers, lakes, and oceans.

Condensation

The process by which water vapor in the air is changed into liquid water, forming clouds.

Transpiration

The process by which water is absorbed by plant roots, moves through plants, and is released as vapor through pores in leaves.

Evaporation

The process by which liquid water is converted into vapor, often due to heat from the sun.

Precipitation

Any form of water, liquid or solid, that falls from the atmosphere and reaches the ground, including rain, snow, sleet, and hail.

Carbon cycle

The series of processes by which carbon compounds are interconverted in the environment, including photosynthesis and respiration.

Nitrogen cycle

The series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms.

Phosphorus cycle

The process by which phosphorus moves through the lithosphere, hydrosphere, and biosphere, primarily through weathering and biological uptake.

Oxygen cycle

The biogeochemical cycle that describes the movement of oxygen within its three main reservoirs: the atmosphere, the biosphere, and the lithosphere.

Hydrosphere

The combined mass of water found on, under, and above the surface of a planet, including oceans, rivers, lakes, and groundwater.

Atmosphere

The layer of gases surrounding a planet, held in place by gravity, which is essential for life on Earth.

Biosphere

The global sum of all ecosystems, representing the zone of life on Earth, including land, water, and the atmosphere.

Geosphere

The solid part of the Earth, consisting of the crust all the way down to the core, which includes rocks, minerals, and landforms.

Lithosphere

The rigid outer layer of the Earth, consisting of the crust and upper mantle, which is involved in tectonic activity.

Fossil fuels

Natural fuels formed from the remains of ancient plants and animals, such as coal, oil, and natural gas, used for energy.