Earth science

Cotopaxi: Ecuador's high active stratovolcano Cotopaxi Cotopaxi is a prominent active stratovolcano in Ecuador, famed for its snow-capped summit near the equator, frequent explosive activity, glacial hazards, and close scientific monit…

Crater: Impact and Volcanic Depressions on Planetary Surfaces Crater A crater is a bowl-shaped depression on a planetary surface formed mainly by impacts or volcanic activity; this article explains types, formation, morphology, examples, and scienti…

Craton: the stable cores of continental lithosphere Craton A craton is an ancient, stable portion of continental lithosphere with thick crust and deep, cold roots. Cratons include exposed shields and sediment-covered platforms and host key…

Cretaceous Period: geology, climate, life, and the end‑Cretaceous event Cretaceous The Cretaceous (about 145–66 million years ago) was the final period of the Mesozoic, marked by high sea levels, chalk deposition, angiosperm rise, diverse dinosaurs, and the mass…

Cryogenian Period Cryogenian Geological period (≈720–635 million years ago) marked by extreme Neoproterozoic glaciations, tectonic reorganization, and important biological and geochemical changes preceding the…

Cryosphere: Earth's frozen water and its role in climate Cryosphere The cryosphere comprises Earth's frozen water—sea ice, glaciers, snow, ice sheets and permafrost—and influences climate, sea level, hydrology, ecosystems and human activities.

Cryovolcano (ice volcano): cold eruptions on icy worlds Cryovolcano Cryovolcanoes are cold-temperature volcanoes that erupt volatile liquids or gases (water, ammonia, methane) on icy moons, dwarf planets and other cold bodies, reshaping surfaces an…

Cyclone (meteorology): structure, types, formation and impacts Cyclone Cyclone: a rotating low-pressure weather system. Covers definitions, core structure, types (tropical, extratropical, tornadoes), formation (cyclogenesis), hazards, and planetary ex…

Cyclone Kyarr (October 2019) Cyclone Kyarr October 2019 super cyclonic storm in the Arabian Sea. Kyarr strengthened to rare ‘super cyclonic’ intensity, stayed over open water and produced high seas and coastal rainfall acro…

Cyclone Yasi (2011) — Major Queensland tropical cyclone Cyclone Yasi An overview of Tropical Cyclone Yasi, a powerful Category 5 storm that struck northern Queensland, Australia in February 2011, its impacts on communities, agriculture and ecosystem…

Daikakuji Seamount — extinct guyot in the Hawaiian–Emperor chain Daikakuji Seamount Daikakuji Seamount is an extinct flat-topped submarine volcano (guyot) in the Hawaiian–Emperor seamount chain of the Pacific Ocean. It records hotspot volcanism, erosion and subsid…

Dark adaptor goggles: purpose, design, and uses Dark adaptor goggles Dark adaptor goggles are red-tinted eyewear used to preserve night vision and reduce glare for meteorological and observational tasks; they trade color and depth perception for fas…

Denudation (geology): processes that lower and reshape Earth's surface Denudation Denudation comprises the physical processes—weathering, erosion, transport and mass wasting—by which water, ice, wind, waves and human activity wear down and redistribute Earth's s…

Deposition (geology): processes, environments, and significance Deposition (geology) Deposition is the geological process by which transported material settles to form sediments and landforms. This article explains mechanisms, environments, sedimentary records, and…

Desert climate (arid climate): characteristics, distribution and significance Desert climate Arid or desert climates receive very little precipitation, feature high evaporation and large temperature swings, and occur in subtropical highs, continental interiors, rain shadow…

Devonian Period (about 419–359 million years ago) Devonian The Devonian is a geologic period in the Paleozoic marked by diverse marine life, the rise of forests and seed plants, and the first vertebrates venturing onto land — a key chapter…

Dew: Formation, Characteristics, Uses and Cultural Significance Dew Dew is water condensed onto surfaces as they cool overnight. This article explains how dew forms, factors that affect it, related phenomena (frost, fog), practical uses, and cultur…

Diabase (dolerite, microgabbro): composition, formation, and uses Diabase Diabase is a fine- to medium-grained mafic intrusive rock (dolerite/microgabbro) rich in plagioclase and pyroxene, forming dikes and sills; used as crushed stone and dimension ston…

Dinosaur Ridge — Morrison Formation fossils and Dakota tracksite near Denver Dinosaur Ridge Dinosaur Ridge, on the Dakota hogback west of Denver, exposes Late Jurassic bone beds and Cretaceous track-bearing sandstones. It is noted for landmark fossil discoveries, public i…

Diorite: Composition, Formation, Characteristics, and Uses Diorite Diorite is a coarse-grained igneous rock intermediate between basalt and granite. This article covers its composition, textures, geologic settings, classification, uses, and how to…

Dip slope (geology) Dip slope A dip slope is a land surface that parallels the dip of rock layers. Common in tilted sedimentary sequences, it shapes cuestas, ridges and hogbacks and influences drainage, stabili…

Dirt: definition, composition, uses, and environmental concerns Dirt Dirt commonly means loose earth or unwanted soil. This article explains its composition, how it forms, differences from soil, practical uses, and environmental and health considera…

Discharge (hydrology): volumetric flow of water in rivers, lakes and streams Discharge (hydrology) Discharge is the volumetric flow of water passing a cross-section per unit time. Covers definition, units, measurement methods, factors that influence flow, uses in management and…

Divergent boundary (constructive plate margin) Divergent boundary A divergent boundary is a plate margin where tectonic plates move apart, forming new crust at mid-ocean ridges or continental rifts and driving seafloor spreading, volcanism, and r…

Dolomite: mineral and rock composed of calcium magnesium carbonate Dolomite Dolomite is a carbonate mineral (CaMg(CO3)2) and the dominant mineral of dolostone. This article covers its composition, textures, origin, uses, and how it differs from limestone.

Dormant volcano A dormant volcano is not currently erupting but retains the potential to do so. This article explains definitions, monitoring signs, hazards, notable examples, and how dormant diff…

Dropsonde: instrument for airborne atmospheric profiling Dropsonde A dropsonde is an expendable atmospheric probe released from aircraft to record vertical profiles of pressure, temperature, humidity and winds — widely used in tropical cyclone rec…

Dunkleosteus — the armored apex predator of the Late Devonian Dunkleosteus Dunkleosteus, a large armored arthrodire placoderm from the Late Devonian (about 360 million years ago), is known for powerful shearing jaws, heavy cranial armor, and a global foss…

Dust — composition, sources, effects, and significance Dust Dust consists of tiny solid particles found in air and on surfaces. This article explains composition, origins (including cosmic dust), impacts on health and environment, measureme…

Dust devil Short-lived, spinning columns of air that lift dust and debris; common in hot, dry landscapes and also observed on Mars. Typically harmless but capable of localized damage and envi…

Dust storm (sandstorm): causes, effects, and mitigation Dust storm A dust storm (sandstorm) lifts loose sand and fine particles into the air, reducing visibility, damaging soils, affecting health and climate, and forming loess deposits far from th…

Dyke (geology): vertical igneous intrusions that cut across rock layers Dyke (geology) A dyke is a tabular body of igneous rock that cuts across preexisting strata. This article covers formation, types, distinguishing features, occurrences and geological significance…

Earth — the third planet from the Sun Earth Earth is the third planet from the Sun, the only known world to support life, with abundant surface water, a layered interior, and a complex biosphere shaped over billions of years…

Earth phase (appearance of the Sun‑lit Earth from the Moon and space) Earth phase The Earth phase is the changing shape of the Sun‑illuminated portion of Earth as seen from the Moon or spacecraft. It cycles with the lunar month, produces earthshine and is comple…

Earth science (geoscience): scope, methods, history and applications Earth science Earth science (geoscience) surveys Earth's systems — atmosphere, hydrosphere, biosphere, lithosphere — their history, methods, and uses in resource management, hazards and environm…

Earth-like planet A planet similar to Earth in size, composition, or orbit; broadly used to mean terrestrial worlds, Earth-sized bodies, or potential Earth analogs among exoplanets.

Earth, Texas Small city in Lamb County, Texas, on the Llano Estacado. A rural agricultural community with a small population (1,109 in 2000), local schools, and a distinctive name noted in popu…

Earth's core: structure, properties, and significance Earth's core The Earth's core is a dense central region with a liquid outer core and a solid inner core. It is characterized by extreme temperatures and pressures and drives the planet's magnet…

Earth's crust: structure, composition, and significance Earth's crust The Earth's crust is the thin, solid outer layer of the planet. This article explains its types, composition, boundaries, formation, and why it matters for life, resources, and pla…

Earth's inner core The inner core is Earth's central, solid region—mostly iron–nickel—revealed by seismic waves; it influences the planet's magnetic field, thermal evolution, and deep-Earth dynamics.

Earth's magnetic field: origin, structure, and effects Earth's magnetic field The geomagnetic field surrounding Earth is generated by motions in the metallic core. It shapes the magnetosphere, guides navigation and animals, varies over time, and records geol…

Earth's mantle: structure, composition, and role in Earth's dynamics Earth's mantle A concise overview of Earth's mantle: its thickness, internal layering, composition, physical properties, role in plate tectonics and volcanism, and how we study it.

Earthborn (novel) — the final book of the Homecoming Saga Earthborn Earthborn is the fifth and concluding novel of Orson Scott Card's Homecoming Saga (1995), blending science fiction and religious themes as it resolves the series' long-running conf…

Earthfall (1995) — fourth novel in the Homecoming Saga Earthfall Earthfall (1995) is the fourth novel in Orson Scott Card's Homecoming Saga, a science-fiction tale that continues a colony's return to Earth and explores faith, leadership and cult…

Earthquake: causes, effects, detection, and societal responses Earthquake An earthquake is the sudden release of energy in Earth's crust that produces seismic waves. This article explains causes, measurements, wave types, hazards such as tsunamis and lan…

Earthsea — Ursula K. Le Guin's fictional archipelago and magic Earthsea Earthsea is the archipelago setting for Ursula K. Le Guin's fantasy stories and novels, noted for a magic system based on True Names, themes of balance and responsibility, and a se…

East Antarctica: geography, climate, ice sheet, and scientific importance East Antarctica East Antarctica, or Greater Antarctica, is the vast, ice‑covered eastern sector of the Antarctic continent, noted for extreme cold, a thick continental ice sheet, and major scienti…

Ectasian (Mesoproterozoic period, 1.4–1.2 billion years ago) Ectasian The Ectasian is the middle period of the Mesoproterozoic (1.4–1.2 Ga), notable for widespread shallow continental shelves, multicellular microfossils, and the earliest convincing e…