Glossary
Find a term from the labs, understand the process behind it, and see how it appears in the landscape. Each entry connects an explanation with a real observation and a model you can explore.
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417 matching terms
The mineral soil layer near the surface, where organic matter mixes with sand, silt and clay. Its darker colour often reflects humus, but colour alone does not establish fertility or the depth of the layer.
Calciustoll near Ponce, Puerto Rico: a Mollisol with a roughly 30 cm mollic surface over a calcic horizon. Its parent material includes colluvium and weathered limestone.
Corrasion
The wearing away of rock by sediment carried against it by water, wind or ice. Look for scratches, polished surfaces or potholes. Unlike attrition, abrasion describes damage to the surface being struck, rather than collisions between transported particles.
Presque Isle River, Michigan. Sediment circulating in eddies abrades the bedrock, enlarging these potholes.
The transfer of radiation into a material, increasing its internal energy. Dark ground often absorbs more sunlight than bright snow. Absorption differs from reflection, which sends radiation away, and transmission, which lets it pass through.
This CERES observation maps reflected sunlight. Solar absorption by the Earth system is the incoming shortwave energy minus this reflected component; the image measures reflection rather than absorption directly.
The removal of water by people from a river, lake or aquifer for uses such as irrigation or drinking supplies. A store can shrink when abstraction and other losses exceed recharge, even though water continues circulating globally.
Groundwater hand pump at Perambalur, India. Abstraction removes water from an aquifer; pumping may lower the water level around a well, which is measured below ground.
The ground above permafrost that thaws in summer and freezes again in winter. Its thickness changes with local climate, vegetation and soil. Seasonal thaw of this layer does not necessarily mean that the underlying permafrost has disappeared.
Patterned ground in Alaska's Noatak region. The active layer above permafrost thaws and refreezes seasonally; surface patterns show freezing processes, but active-layer depth needs field measurements.
Cooling as an air parcel expands when pressure falls, without exchanging heat with its surroundings. Rising air commonly cools this way.
Cloud streets over the Bering Sea, 20 January 2006. Cold air over warmer water supports convection organised into rolls by the wind.
Köppen tropical rainforest climate: every month averages at least 18 °C and receives at least 60 mm of precipitation.
Tropical forest at Bodiman, Cameroon. This is a landscape example for tropical rainforest climate; an Af classification is determined from long-term monthly temperature and rainfall, not from vegetation alone.
Volcanoes that get older away from the active centre, recording plate motion.
Hawaii from the ISS. The volcanic chain records Pacific plate motion relative to a long-lived hotspot; the youngest main island is at the southeast end.
A large body of air with broadly similar temperature and moisture characteristics acquired over a source region.
NOAA surface analyses during a late-February 2022 storm. Isobars join equal pressure; front symbols identify analysed boundaries between air masses.
The fraction of incoming sunlight reflected by a surface, expressed from zero to one or as a percentage. Fresh snow usually has a high albedo and dark soil a lower one. Reflected energy in watts per square metre is a flux, not albedo itself.
CERES measures reflected shortwave energy in W m⁻². Albedo is the fraction of incoming sunlight reflected, so obtaining it requires dividing reflected flux by the corresponding incoming flux; the colour scale here is not albedo.
A fold with the oldest rocks in its core. In a simple upright anticline, the layers arch upwards and dip away from the centre; overturned folds can have different geometry.
Folded strata at The Settlands, Wales. Trace a bed through the exposure to see deformation recorded in solid rock.
An atmospheric circulation around a region of high pressure, commonly associated with sinking air. Surface winds turn clockwise in the Northern Hemisphere and anticlockwise in the Southern Hemisphere. Clear skies are common, but fog and low cloud can persist.
NOAA surface analyses during a late-February 2022 storm. Isobars join equal pressure; front symbols identify analysed boundaries between air masses.
Explore further with USGS water glossary · USGS volcano glossary · NPS glacial geology · NASA Earth facts. Photograph acknowledgements are collected on the Image credits page.