Separate storage from movement
A reservoir, sometimes called a pool, is a place where matter is stored. Water reservoirs include oceans, ice, groundwater, the atmosphere, soil, and living things. Water moves among them through processes such as evaporation, condensation, precipitation, runoff, infiltration, and transpiration.
Carbon reservoirs include rocks and sediments, oceans, the atmosphere, soil, and living things. Photosynthesis, feeding, respiration, decomposition, combustion, weathering, and exchange between the ocean and atmosphere move carbon from one reservoir to another.
Matter cycles while energy flows
Water molecules and carbon atoms can be reused as they move through living and nonliving parts of Earth. Energy does not follow that same closed path: it enters most ecosystems as sunlight, supports changes such as evaporation and photosynthesis, and eventually leaves as heat.
A cycle can continue while its rates and storage amounts change. Pumping groundwater, redirecting rivers, changing land cover, or burning fossil fuels can move matter faster, move it to a different reservoir, or alter how long it remains stored there.
Remember these ideas
Key ideas
- Reservoirs store matter; processes move matter between reservoirs.
- Water moves through phase changes, precipitation, surface flow, underground flow, and living things.
- Carbon moves through biological, ocean, atmospheric, and geologic processes.
- Matter cycles through ecosystems, while usable energy flows through and eventually leaves as heat.
Make the reasoning visible
Trace one water path and one carbon path
- 1
Water begins in the ocean reservoir, evaporates into the atmosphere, condenses, and returns to land as precipitation.
- 2
Some of that water infiltrates soil, enters plant roots, and returns to the atmosphere through transpiration.
- 3
A carbon atom begins in atmospheric carbon dioxide, enters a plant through photosynthesis, and can move to a consumer through feeding.
- 4
Respiration or decomposition can return that carbon to the atmosphere; the atom cycles, while energy used along the path is not recycled in the same way.
Try the next step
Label storage and movement
For each pair, identify the reservoir and the movement process: groundwater and infiltration; a forest’s living biomass and photosynthesis.
How could removing vegetation change both water movement and carbon storage?