Category: Geography

Introduction Natural phenomena are observable events produced by Earth’s physical, chemical, and biological systems rather than by human action. They range from luminous atmospheric displays such as the aurora to commonplace cyclical events like sunrise, and are unified by their origin in natural processes and energy exchanges within the environment. These phenomena are conventionally organized…

Introduction Geological phenomena comprise the natural features and processes that geology seeks to explain: they record Earth’s material composition, the operative physical and chemical mechanisms, temporal evolution, and the resulting landforms. These phenomena arise from internal Earth dynamics, surface agents, or their interactions, and are therefore central to reconstructing past environments and assessing present-day hazards….

Introduction Limestone pavements are a distinctive karst morphology in which an exposed, flat limestone surface is incised into a regular, block‑like pattern that resembles man‑made paving. The pattern arises where chemical weathering preferentially dissolves carbonate rock along pre‑existing joints and fractures, producing an orthogonal or sub‑orthogonal network of slabs (clints) separated by deeper fissures (grikes)….

Lava is the molten or partially molten rock expelled from a planet or satellite interior onto the surface—via volcanic vents or crustal fractures—and may be emplaced subaerially or submarine. Typical eruptive temperatures lie between about 800 and 1,200 °C (1,470–2,190 °F); this thermal range governs lava rheology, crystallization kinetics and the development of volcanic landforms….

Introduction A lava dome is a roughly circular, mound‑shaped volcanic landform produced by the slow extrusion of highly viscous lava that, because of limited lateral mobility, accumulates over the vent to form a prominent protrusion. Dome‑building eruptions are most common where magmas are chemically evolved—notably at convergent plate margins—and account for roughly 6% of volcanic…

Introduction — Laurasia Laurasia was the northern continental mass of the late Paleozoic–Mesozoic supercontinent Pangaea, occupying the northern hemisphere portion of the united landmass from the assembly of Pangaea (approximately 335 Mya) until the early stages of its breakup (around 175 Mya). The name reflects its constituent cratons—principally Laurentia and the Eurasian plate—whose amalgamation produced…

Introduction The Laramide orogeny was a principal mountain‑building episode across western North America that initiated in the Late Cretaceous (roughly 80–70 Ma) and waned during the early Paleogene (somewhere between ~55 and 35 Ma); precise onset, termination and cumulative duration remain debated and the deformation occurred in episodic pulses separated by relative quiescence rather than…

Introduction A landform is a discrete morphological feature of the solid surface of a planetary body—on Earth or elsewhere—formed or modified by natural processes and, in some cases, by human activity. Together, landforms make up the physical fabric of a terrain, whose pattern of elevation, slope and relief is captured by the concept of topography….

Introduction The Kuroshio Current (Japanese: 黒潮, “Black Tide”; also Japan or Black Current, 日本海流) is a warm, northward western-boundary current on the western flank of the North Pacific, named for its deep blue waters. As the Pacific analogue of the North Atlantic’s Gulf Stream, it carries tropical heat poleward as the western limb of the…

Introduction The Jura Mountains (IPA: /ˈdʒʊərə, ˈʒʊərə/; anglicized JOOR‑ə, ZHOOR‑ə) are a sub‑alpine chain lying immediately north of the Western Alps. They form a conspicuous physiographic element that largely traces a long segment of the French–Swiss boundary and provides a continuous upland link from the Alpine foreland into northern Switzerland and southwestern Germany. Geomorphologically the…

Introduction Isostasy denotes the gravitational equilibrium in which Earth’s crust or lithosphere “floats” on the denser, deformable mantle or asthenosphere, producing and maintaining variations in surface elevation through buoyancy. The elevation of a crustal block is determined quantitatively by its thickness and density: relatively thick or low-density crust attains greater buoyant heights, whereas thin or…

Introduction The ionosphere is the ionized region of Earth’s upper atmosphere, occupying a vertical extent roughly from 48 km to 965 km above mean sea level; it includes the thermosphere and overlaps the upper mesosphere below and the lower exosphere above. Solar extreme ultraviolet and X‑ray radiation ionize neutral constituents, producing populations of free electrons…

Introduction Intraplate earthquakes are seismic events that originate within the interior of a tectonic plate rather than along plate boundaries. Although less frequent than interplate earthquakes, they may concentrate on pre‑existing zones of mechanical weakness far from active margins. Because regions distant from plate boundaries are often not engineered or retrofitted for seismic loading, intraplate…

The topography of central East Asia is dominated by an elevated region comprising the Tibetan Plateau and adjacent ranges such as the Tien Shan; this broad swath of high relief reflects extensive crustal shortening and uplift across the continental interior rather than isolated orogenic fronts. The pervasive nature of these landforms indicates that the mechanical…

Introduction Interplate earthquakes originate at the contacts between tectonic plates, where accumulated stress is released as relative displacement across faults and radiated as seismic waves through the Earth. These boundary events account for the vast majority of global seismic energy release—over 90 percent—and include the largest known earthquakes, particularly those that occur on subduction interfaces…

Introduction Earth’s interior (excluding atmosphere and hydrosphere) is organized in concentric shells: a silicate crust and overlying lithosphere, a mechanically weaker asthenosphere, the solid mantle, a convecting liquid outer core whose motion sustains the geomagnetic field, and a solid inner core. This stratification is routinely represented in geological cross‑sections and underpins models of heat and…

An inland sea (also called an epeiric or epicontinental sea) is a shallow, continental-scale body of marine water that occupies broad interior basins or epicontinental platforms and differs fundamentally from ordinary lakes by its partial marine character and large areal extent. Such seas may be entirely surrounded by land or retain one or more hydrological…

Introduction — Indian Plate The Indian plate is a minor tectonic plate situated across the equator in the Eastern Hemisphere whose status as a distinct plate has been subject to debate. It originated as part of the Gondwana supercontinent and rifted away roughly 100 million years ago, migrating northward while transporting the continental fragment often…

Introduction The Indian Ocean is one of five cartographically defined oceanic divisions—alongside the Pacific, Atlantic, Arctic, and Southern/Antarctic Oceans—whose map boundaries are practical conventions rather than discrete geological separations. Within its basin are numerous marginal seas that occupy continental margins and impose distinct hydrographic and ecological conditions; notable examples include the Arabian Sea, the Bay…

Introduction Igneous rock—from the Latin igneus, “fiery”—constitutes one of Earth’s principal rock types and forms by the cooling and solidification of molten rock (magma or lava). Magma is generated by partial melting of pre‑existing mantle or crustal materials; melting is initiated principally by increases in temperature, reductions in pressure, or compositional changes such as volatile…

Homo sapiens is one species within the hominid family of primates, a lineage that shares a single common ancestry with the other great apes and traces its roots across Africa and Asia. The emergence of anatomically modern humans reflects a suite of derived traits—habitual bipedalism, refined manual dexterity and capacities for complex symbolic communication—superimposed on…

A hoodoo is a slender, pillar-like rock formation produced by erosion; comparable features are commonly referred to as tent rocks, fairy chimneys, or earth pyramids. Morphologically, a hoodoo consists of a relatively soft-rock column capped by a more resistant stone whose greater durability retards downward erosion and thereby shields the underlying shaft. Such forms develop…

Introduction Physical cosmology investigates the origin, large‑scale arrangement, composition, dynamics and ultimate fate of the Universe by combining theoretical models with empirical tests. The modern Big Bang paradigm—in which the cosmos evolves from an initially extremely hot, dense state and expands thereafter—was first cast into a quantitative framework by Georges Lemaître in 1927. Empirical support…

The scientific inquiry into the origin and evolution of the Solar System finds its formal roots in the Copernican Revolution, which reframed astronomical thought and established the conceptual basis for later theories of planetary formation and dynamics. The term “Solar System” itself appears in the literature by 1704, signalling the emergence of a modern planetary…

Introduction The Geological Time Scale (GTS) is the internationally accepted framework for subdividing Earth history into named eons, eras and periods; it expresses ages in Ma (million years ago) and organizes geological and biological events into a standardized chronology from planetary formation to the present. Earth accreted from the solar nebula about 4.54 billion years…

The Himalayas are a dominant orographic feature of southern Asia, forming the principal physical barrier between the lowland Indo‑Gangetic Plain and the high Tibetan Plateau and containing some of the planet’s highest summits, including Mount Everest. Oriented along a west‑northwest to east‑southeast arc approximately 2,400 km long, the range is anchored by Nanga Parbat in…

Introduction A guyot (pronounced /ˈɡiː.oʊ, ɡiːˈoʊ/; also called a tablemount) is a volcanic submarine landform defined by an isolated seamount whose summit is distinctly flattened and lies submerged more than 200 m (≈660 ft) below mean sea level. These flat tops can form extensive, relatively level platforms with diameters that may exceed 10 km (≈6…

Introduction Satellite gravimetry (notably NASA’s GRACE mission) maps departures of Earth’s gravity field from an idealized smooth reference surface—the terrestrial ellipsoid—revealing positive anomalies (stronger gravity; commonly shown in red) and negative anomalies (weaker gravity; shown in blue). These spatial variations reflect heterogeneity in Earth’s internal mass distribution and its temporal changes. The gravity of Earth…

Gondwana was a principal Paleozoic–Mesozoic continental assembly whose constituent cratons now form roughly two thirds of present-day continental area, including South America, Africa, Antarctica, Australia, Zealandia, Arabia and the Indian subcontinent. Its construction began in the Neoproterozoic, with accretionary collisions such as the East African Orogeny (c. 800–650 Ma) that sutured India and Madagascar to…

Landform classification relies on a suite of observable, measurable physical attributes that together define a terrain feature’s identity and behaviour, enabling comparison across regions and scales beyond naming conventions. Chief among these attributes is origin: the formative agent (e.g., tectonic uplift, volcanism, fluvial processes, glaciation, coastal dynamics, aeolian transport, mass-wasting) largely determines a landform’s internal…

Introduction A glacier is a persistent, concentrated mass of dense ice that behaves as a geomorphic material: it deforms internally and flows downslope under its own weight. Glaciers develop where multi‑year snow accumulation consistently exceeds ablation, yielding a self‑driven body of ice that transmits stress, moves, and progressively modifies its bed and surrounding landscape. Flow…

The geothermal gradient quantifies how temperature increases with depth within a planetary interior, commonly reported as °C km−1 (equivalently K km−1 or mK m−1). In stable continental crust away from plate boundaries this near-surface gradient is typically on the order of 25–30 °C km−1, implying a temperature rise of roughly 25–30 °C per kilometre. Atmospheric…

Introduction The geosyncline was a nineteenth– and early twentieth–century framework for explaining orogeny in which vast, long-lived downward folds or troughs in the crust accumulated thick sedimentary sequences prior to mountain building. In this model, continued deposition within the trough created a heavy sediment pile that was later buoyantly readjusted—through processes described as isostatic uplift—so…

Geomorphosites — Introduction A geomorphosite is a landform or assemblage of landforms that attains significance beyond its physical form through scientific, educational, historic‑cultural, aesthetic or socio‑economic values, and thereby becomes an element of natural heritage warranting study, protection and interpretation. As a category, geomorphosites form a subset of geoheritage (geosites) and encompass a broad range…

Geomorphology is the scientific study of the origin, form and evolution of Earth’s surface features—both continental topography and submarine bathymetry—shaped by physical, chemical and biological agents operating at or near the surface. The discipline’s name, from the Greek gê (earth), morphḗ (form) and lógos (study), underscores its central concern with landform form and the systematic…