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Introduction — Passive margin A passive margin is the lithospheric transition between continental and oceanic domains that is not an active plate boundary; it records a former rifted edge of a continent that presently lacks plate‑boundary seismicity, active convergence, or subduction. These margins originate through a rifting‑to‑spreading evolution in which continental extension progresses to the…

Pancake domes — Introduction Pancake domes are a distinctive class of volcanic edifice found on Venus, representing a morphotype unique to Venusian volcanism. Individual examples, notably the Carmenta Farra group, illustrate their characteristic form. These domes are broadly scattered across the planet, typically occurring in clusters; however, such clusters contain fewer individual domes than the…

Introduction Paleomagnetism is the branch of geophysics that reconstructs Earth’s past magnetic field by analyzing magnetic signals locked into rocks, sediments and archaeological materials. Ferromagnetic minerals acquire a stable remanent magnetization during formation or early diagenesis that records the ambient geomagnetic vector (direction and intensity); these preserved signals serve both as archives of field behavior…

Introduction The Paleogene Period (66.00–23.04 Ma) is the opening interval of the Cenozoic Era and the tenth period of the Phanerozoic Eon, encompassing 43 million years of Earth history. It is formally divided into three successive epochs—Paleocene, Eocene, and Oligocene—each recording distinct phases of environmental and biotic change within the 66–23.04 Ma span. Nomenclatural variants…

Introduction — Pacific Plate The Pacific Plate is the largest oceanic tectonic plate, underlying the Pacific Ocean and encompassing roughly 103 million km2. It originated in the Early Jurassic, about 190 million years ago, as a small plate that formed at a triple junction between the Farallon, Phoenix, and Izanagi plates. Once established, the plate…

P wave — Introduction The P wave (primary or pressure wave) is the fastest seismic body wave and therefore normally constitutes the first clear phase recorded at a site following an earthquake. It is a compressional wave that propagates by alternately compressing and dilating material in the direction of travel, and unlike shear waves it…

Introduction From space the ozone layer is visible as a narrow blue band at Earth’s limb, lying within the lower edge of the broader stratospheric glow and commonly seen above the orange twilight of the troposphere, where cloud tops such as cumulonimbus appear in silhouette. Physically, the ozone layer denotes the region of the stratosphere…

Introduction Plate tectonics provides the overarching framework for understanding the behavior of the Earth’s outer rigid shell, the lithosphere, which is segmented into rigid plates that move horizontally over a weaker, ductile asthenosphere. This system of relative plate motions accounts for the global patterns of earthquakes, volcanism, mountain building, the opening and closing of ocean…

Introduction — Outline of Earth Sciences Earth science, often termed geoscience or the geosciences (and occasionally referenced as “Earthquake sciences”), comprises the collective scientific disciplines that investigate planet Earth. Situated within the physical sciences and the wider natural sciences, it employs empirical, physics-based and quantitative methods to observe, model and explain Earth’s systems. Earth’s unique…

Introduction Orogeny denotes the principal mountain‑building process that operates at convergent plate boundaries, where compressive plate motions deform, thicken and uplift crustal segments to form orogenic belts (orogens). Orogenesis encompasses a range of concurrent and successive geological processes: large‑scale structural deformation of pre‑existing continental crust (notably folding, thrusting, faulting and crustal thickening) together with syntectonic…

Introduction Oceans, which cover roughly 71% of Earth’s surface, dominate the planet’s geography and are fundamental to its capacity to support life. Geologic–biologic events from the Hadean through the Archean, Proterozoic and Phanerozoic eons (ca. 4,500–0 Ma) record the progressive emergence of water and life: formation of the planet and earliest evidence for water, the…

The Okinawa plate, often termed the Okinawa platelet, is a minor continental tectonic block located in the northern and eastern hemispheres. It extends along a north–south corridor from the northern extremity of Taiwan to the southern tip of Kyūshū and occupies the marine and insular domain between those landmasses, incorporating features such as Kikai Island…

Introduction The Okhotsk Plate is a minor tectonic block occupying northeastern Asia and adjacent seas, including the Kamchatka Peninsula, Magadan Oblast, Sakhalin Island, the Sea of Okhotsk, the Kuril Islands (disputed), and parts of northern Japan (Hokkaidō, Kantō and Tōhoku). Its position defines a discrete crustal entity whose boundaries coincide with major zones of deformation…

Introduction The contemporary account of India’s oil and gas industry begins with an explicit caveat: the source material (dated August 2025) incorporates text from a large language model and may contain hallucinated details or unverified references, so assertions and citations should be critically assessed and any copyright or unverifiable claims removed before reuse. Commercial petroleum…

Introduction — Oceanic crust Oceanic crust forms the outermost layer of Earth’s oceanic plates and, together with the immediately underlying rigid portion of the upper mantle, constitutes the oceanic lithosphere. It is markedly different from continental crust in composition, thickness and density: typically under 10 km thick and with a mean density near 3.0 g…

Introduction An oceanic (or ocean) basin can be understood from two complementary perspectives. Hydrologically, it denotes any part of the Earth’s surface covered by seawater; geologically, it refers to extensive subsiding basins—broad depressions below sea level—occupied by the oceans. Ocean basins are most commonly delineated on the basis of continental distribution, a convention that yields…

Introduction The ocean covers roughly 70.8% of Earth’s surface and is customarily partitioned into five principal basins—the Pacific, Atlantic, Indian, Southern (Antarctic) and Arctic—which are further subdivided into seas, gulfs and other named marine basins. Containing about 97% of the planet’s water, the ocean dominates the hydrosphere and functions as a vast thermal reservoir and…

Introduction — Ocean world An ocean world is a planet or natural satellite whose hydrosphere includes substantial liquid, either at the surface—potentially inundating all continental land—or as subsurface oceans beneath an outer shell. The broader concept of a thalassogen recognizes that such oceans need not be liquid water: other fluids (for example molten rock, eutectic…

Introduction The North Atlantic Current (NAC), often termed the North Atlantic Drift or North Atlantic Sea Movement, is the northeastward continuation of the Gulf Stream and functions as a major warm western‑boundary current in the North Atlantic. As the initial poleward branch of the North Atlantic Subpolar Gyre, the NAC conveys western‑boundary flow from subtropical…

North American Plate — Introduction The North American Plate is a principal tectonic plate with an area of approximately 76 million km² (29 million mi²), making it the second-largest plate on Earth. Its surface encompasses most of the North American continent, Greenland, portions of northeastern Siberia, and several adjacent island territories including Cuba, the Bahamas,…

Newton’s law of universal gravitation posits that every pair of mass elements attracts each other with a force proportional to the product of their masses and inversely proportional to the square of the distance between their centers of mass. In its usual quantitative form, F = G m1 m2 / r^2, where F is the…

The New Madrid seismic zone (NMSZ), also described in the literature as the New Madrid fault line, fault zone, or fault system, is a principal source of intraplate earthquakes in the conterminous United States. Unlike plate-boundary seismicity, intraplate earthquakes originate within a tectonic plate; the NMSZ exemplifies how reactivated crustal structures well inland from plate…

Introduction The neural tube is the embryonic structure that gives rise to the central nervous system—the brain and spinal cord—in chordates, including all vertebrates. Its formation begins with the appearance of a neural groove flanked by paired neural folds; as morphogenesis proceeds the groove deepens, the folds elevate and converge at the midline, and their…

Introduction — Nebular hypothesis The nebular hypothesis, originally proposed by Immanuel Kant and later reformulated by Pierre Laplace, is the foundational cosmogonic model in which the Solar System originates from a rotating disk of gas and dust surrounding a young Sun. Its modern incarnation, the solar nebular disk model (SNDM), retains the core idea of…

The Nazca (Nasca) plate is an oceanic tectonic plate located in the eastern Pacific basin immediately offshore of western South America. Bounded to the west by the Pacific Plate and to the south by the Antarctic Plate, these margins are expressed respectively by the East Pacific Rise and the Chile Rise. Along its eastern boundary…

Introduction India’s land and water endowments remain central to its natural-resource profile. In 2020 the country possessed approximately 155.37 million hectares of cultivable land, equivalent to about 52.3% of its territorial area; however, this agricultural land is under pressure and showing contraction due to intensive cropping, expanding livestock grazing, deforestation, urban expansion and an increase…

Introduction A natural arch (also called a natural bridge or rock arch) is a freestanding, arch‑shaped rock formation defined by a span of rock with an opening beneath. Such landforms arise where erosional agents remove weaker rock beneath a more resistant caprock, leaving an overhead arch and a void. They commonly occur on inland and…

Introduction Mud volcanoes are eruptive landforms produced by the ascent and surface discharge of mud slurries, water and associated gases; smaller, localized seepage features of the same process are often called mud‑pots. Individual edifices span a broad morphological spectrum, from shallow seeps under a metre high and a few metres across to extensive mud‑dome complexes…

Mountain ranges arise from large‑scale movements of the Earth’s crust and are produced by multiple, interacting orogenic processes — notably folding, faulting, volcanic activity, igneous intrusion and metamorphism. These mechanisms operate together to thicken, deform and build topography rather than acting in isolation. Under compressive regimes at convergent plate boundaries, brittle failure generates low‑angle thrusts…

Beaches are continually reshaped by hydrodynamic forces: waves, currents, tides and fluvial flows erode coastal and terrestrial materials and redistribute the resulting sediment along the shore. Over long intervals, repeated physical weathering and transport reduce bedrock and coarser deposits to sand-sized grains that accumulate onshore and generate the characteristic cross-shore beach profile. Fluvial systems contribute…

Introduction Mining constitutes a significant component of India’s economy, contributing roughly 2.2–2.5% of national GDP and a markedly larger share—about 10–11%—of the industrial sector’s output. Artisanal and small-scale operations exert a measurable influence on the sector’s cost structure, accounting for approximately 6% of total mineral production costs, while direct employment in mining is reported at…

Introduction (Minerals) A mineral is a naturally formed, crystalline chemical element or compound produced by geologic processes, characterized by a reasonably well‑defined chemical composition and an ordered crystal structure. By convention the geologic definition normally excludes substances known only from living organisms, yet exceptions exist: some minerals are biogenic (e.g., calcite produced by organisms), some…

Introduction The Milky Way is a barred spiral galaxy that contains the Solar System and, when seen from Earth, appears as a luminous, unresolved band produced by the combined light of innumerable stars concentrated in its spiral arms. Morphologically a barred spiral, its optically defined D25 isophotal diameter is estimated at 26.8 ± 1.1 kpc…

Introduction — Mid‑ocean ridge A mid‑ocean ridge (MOR) is a linear, submarine mountain system formed where tectonic plates diverge and new oceanic lithosphere is created. Typically found at depths near 2,600 m and standing roughly 2,000 m above the adjacent abyssal plains, these ridges are the topographic highs of the ocean floor produced as mantle…

Metamorphism denotes the transformation of a pre‑existing rock (the protolith) into a new lithology through changes in mineralogy and texture while the rock remains solid; melting to form magma does not occur. These transformations typically take place at temperatures above ~150 °C and commonly under elevated pressures and in the presence of chemically active fluids,…