Earth science

Canary Current — eastern boundary current of the North Atlantic Canary Current The Canary Current is a broad, slow-moving eastern boundary current off northwest Africa. It drives coastal upwelling, supports rich fisheries, and has shaped regional climate and…

Carbon cycle: movement of carbon through Earth's systems Carbon cycle Overview of how carbon circulates among atmosphere, biosphere, oceans, soils and rocks, the processes that drive it, and how human activity alters the balance.

Carbon sequestration: methods, storage, and role in climate mitigation Carbon sequestration Carbon sequestration is the capture and long-term storage of atmospheric carbon dioxide through biological, geological, and engineered methods to reduce greenhouse gas concentratio…

Carboniferous Period Carboniferous Geological period (≈359–299 Ma) marked by vast coal-forming forests, high atmospheric oxygen, amphibian and insect diversification, and major stratigraphic subdivisions (Mississipp…

Cascade Volcanic Arc A chain of volcanic centers in the Pacific Northwest stretching from British Columbia to northern California, formed by subduction and including many prominent stratovolcanoes and…

Cassiterite — the primary tin oxide mineral (SnO2) Cassiterite Cassiterite is the chief ore of tin (SnO2). A dense, hard oxide mineral, it forms prismatic crystals and placer deposits and is the main source of metallic tin for industry and met…

Catastrophism: historical concept of sudden geological and biological change Catastrophism Catastrophism asserts that Earth has been shaped by intermittent, often violent events that caused rapid geological and biological change. The idea influenced 19th‑century science…

Cave diving: exploration, risks, and scientific value Cave diving Cave diving applies scuba techniques to explore flooded caves. It requires specialized training, redundant equipment, and strict safety practices; it supports science, archaeology,…

Ceiling balloon (pilot balloon) — measuring cloud base by ascent timing Ceiling balloon A ceiling balloon (pilot balloon) is a simple meteorological method to estimate cloud-base height by timing a balloon with a known ascent rate until it disappears into the cloud.

Cementation (geology): how loose sediment becomes solid rock Cementation Cementation is the diagenetic process by which minerals precipitate in pore spaces and bind sediment grains into sedimentary rock, reducing porosity and altering rock properties.

Central Atlantic Magmatic Province: origin, characteristics, and significance Central Atlantic magmatic province Large late-Triassic continental flood-basalt province spanning Pangaea margins. Overview of its geology, timing, links to Pangaea breakup and the end‑Triassic crisis, and its globa…

Central Pacific Hurricane Center U.S. forecasting center responsible for monitoring and warning for tropical cyclones in the central North Pacific (140°W to the International Date Line), based in Honolulu and oper…

Cerro Bonete (Bolivia) — high volcanic peak in Sur Lípez Cerro Bonete (Bolivia) Cerro Bonete is a 5,630 m volcanic summit in southwestern Bolivia's Sur Lípez province. It lies in the high Andes / Altiplano region and forms part of the region's volcanic landsca…

Chalk: sedimentary rock and common chalk materials Chalk Chalk is a soft, white, porous form of limestone formed from microscopic marine skeletons; the term also applies to several manufactured writing and marking materials with differen…

Chert — a hard silica rock (flint, jasper, agate) Chert Chert is a dense, fine‑grained sedimentary rock made of microcrystalline quartz. It forms nodules and beds, preserves fossils, and has been used for tools, construction aggregate,…

Chevron (geology) A chevron is a sharply angular fold in layered rocks, typically forming V-shaped stacks of beds in response to compression; common in alternating hard and soft sediments such as tu…

Chicxulub crater A buried multiring impact basin beneath Mexico’s Yucatán Peninsula linked to the end‑Cretaceous mass extinction; its discovery, structure, evidence and ongoing research.

Chilcotin Group: basaltic plateau volcanism of British Columbia Chilcotin Group A broad volcanic plateau of Miocene–Pleistocene basalt flows in British Columbia’s Interior Plateau. Covers up to ~50,000 km², volume ~3,300 km³; active mainly 6–10 and 2–3 Ma with…

Chinese scholars' rocks: history, qualities, and cultural significance Chinese scholar's rocks Scholars' rocks (gongshi) are naturally formed stones prized in Chinese literati culture for their shape, texture and symbolic value. Used indoors and in gardens, they influenced E…

Chinook: the warm, snow‑melting mountain wind of the Rockies Chinook Chinook winds are warm, dry downslope winds that rapidly raise temperatures east of the Rocky Mountains, often melting snow. They are a regional form of foehn wind with characteris…

Chogolisa (Bride Peak) — Karakoram mountain in Gilgit‑Baltistan, Pakistan Chogolisa Chogolisa, or Bride Peak, is a 7,665 m mountain in Pakistan’s Karakoram. Noted for multiple summits, long snow ridges and difficult glaciated approaches; its highest summit was fir…

Christmas 1994 nor'easter A strong coastal cyclone that developed in the Gulf of Mexico and moved up the U.S. East Coast in late December 1994, bringing heavy snow, coastal flooding, high winds and major ho…

Chron (geology): short geological time interval Chron A chron is a short geologic time interval used in Earth sciences—commonly in magnetostratigraphy and biostratigraphy—to mark brief episodes of geological or biological change.

Clastic rock: sedimentary rocks made of broken fragments (clasts) Clastic rock Clastic rocks are sedimentary rocks composed of fragments (clasts) of pre-existing rock. Classified by grain size, shape and sorting, common types include conglomerate, breccia, sa…

Clay: composition, properties, origins, uses and engineering impacts Clay Clay is a fine-grained soil and rock material composed mainly of clay minerals. This article explains its composition, formation, common uses (pottery, bricks, drilling), engineeri…

Cleveland-Lloyd Dinosaur Quarry A Late Jurassic fossil site in central Utah famed for the highest known concentration of dinosaur bones from the Morrison Formation and an unusually large number of carnivore remai…

Cliff: steep natural rock faces, formation, types and notable examples Cliff A cliff is a steep or vertical rock face formed by erosion, faulting or mass movement; common on coasts, mountains and river valleys and composed of resistant rock strata.

Climate: long-term patterns of weather, types, causes and relevance Climate Climate is the long-term pattern of weather in a region — averages and ranges of temperature, precipitation, wind and related conditions — shaped by geography, oceans and atmospher…

Climate change: causes, history, impacts and human responses Climate change Accessible overview of climate change: how Earth's climate system works, natural and human drivers, evidence from past and present, impacts, uncertainties, and responses including…

Climate of California: regional types, causes, and impacts Climate of California Summary of California’s varied climate zones, the physical factors that shape them, their seasonal patterns, and key impacts on water, agriculture, and wildfire risk.

Climate sensitivity: how Earth's temperature responds to greenhouse forcing Climate sensitivity Climate sensitivity measures how much global temperature changes after a sustained change in radiative forcing, commonly defined as the warming from a doubling of atmospheric CO2.

Climatology: study, methods, history, and applications Climatology Climatology is the scientific study of climate—long-term patterns of weather—covering measurement, analysis, models, history, and practical uses in forecasting, planning, and envir…

Cloud (meteorology): formation, types, and roles in the water cycle Cloud A cloud is an airborne collection of tiny liquid droplets or ice crystals. This article explains how clouds form, their structure and types, roles in weather and climate, and impor…

Coal: composition, formation, uses, and environmental impacts Coal Coal is a combustible sedimentary rock formed from ancient plant matter; used for energy and industry, it shaped the Industrial Revolution and now raises health and climate concern…

Coal ball (permineralized peat fossils) Coal ball Coal balls are permineralized masses of peat or plant debris occurring within coal seams, commonly calcareous, that preserve cellular anatomy and inform studies of ancient swamp ve…

Coal mining: methods, history, uses, and impacts Coal mining Coal mining is the extraction of coal from the ground. This article explains methods, historical development, uses in energy and industry, and environmental and safety consideratio…

Cobble (geology) A cobble is a clast between pebble and boulder size (commonly 64–256 mm). This article covers definition, formation settings, sedimentary significance, uses, measurement and distin…

Coccoliths: microscopic calcium‑carbonate plates produced by coccolithophores Coccolith Coccoliths are minute calcium‑carbonate plates created by single‑celled algae (coccolithophores). They build coccospheres, form large parts of chalk and deep‑sea sediments, and inf…

Cocos Plate A relatively young oceanic tectonic plate in the eastern Pacific off Central America; formed by the breakup of an older plate and subducting beneath Central America to create volca…

Cold seep (cold vent) Cold seep Cold seeps are seafloor areas where methane, hydrogen sulfide and other hydrocarbons escape, sustaining chemosynthetic communities, forming carbonate deposits and altering local se…

Conglomerate (geology) A sedimentary rock composed of rounded gravel-size clasts set in finer matrix or cement; indicates high-energy transport and records provenance, environment, and diagenetic history…

Continental crust The continental crust is Earth's relatively light, thick outer layer beneath continents and shelves, composed mainly of felsic rocks; it differs from oceanic crust in composition,…

Continental drift Continental drift is the hypothesis that Earth's continents move slowly across its surface; it laid the foundation for the modern theory of plate tectonics and explains the distrib…

Continental margin The continental margin is the submerged edge of a continent where continental crust meets oceanic crust; it includes the shelf, slope and rise and plays a key role in sedimentation…

Convergent boundary (plate tectonics) Convergent boundary A plate boundary where two tectonic plates move toward each other, causing subduction, mountain building, trenches, earthquakes and volcanic arcs in different combinations.

Coprolite — fossilized feces and what it reveals Coprolite Coprolites are fossilized animal droppings (trace fossils) that preserve dietary remains and ecological information; used by paleontologists to reconstruct ancient diets and enviro…

Corundum — the aluminium oxide mineral behind ruby and sapphire Corundum Corundum (Al2O3) is a very hard crystalline form of aluminium oxide that yields gem varieties ruby and sapphire. It is valued for gemstones, abrasives, industrial components and op…

Cotacachi Volcano: Dormant Andean Peak in Imbabura, Ecuador Cotacachi Volcano Cotacachi is a dormant stratovolcano in the northern Ecuadorian Andes, rising to 4,944 m. It forms a prominent snow‑capped landmark above Cotacachi town and shapes local ecology, r…