Author: user

Introduction — Tropical Deserts Tropical deserts occupy a broad circumglobal belt roughly between 15° and 30° latitude on either side of the Equator and include many of the planet’s major hot deserts. Climatically they are defined by very high mean monthly temperatures, producing some of the warmest surface environments on Earth, and by extreme, persistent…

Introduction The Trobriand Plate is a small tectonic microplate located east of New Guinea in the marine domain between New Guinea and the Solomon Islands, occupying a portion of the complex plate boundary zone in the southwestern Pacific. Geologically the region is notable for hosting some of the youngest metamorphic core complexes on Earth, evidence…

Introduction A triple junction is the point where the plate boundaries of three tectonic plates converge; each adjoining boundary must belong to one of the three fundamental boundary types—ridge (R: divergent/mid‑ocean spreading), trench (T: convergent/subduction), or transform fault (F: strike‑slip)—and the junction is classified by that specific combination (for example, F–F–T or R–R–R). Diagrams typically…

Introduction Travertine (pronounced /ˈtrævərtiːn/, TRAV-ər-teen) is a continental variety of limestone produced by mineral precipitation from spring waters, most notably those issuing from geothermal (hot) springs. Its accumulation involves rapid deposition of calcium carbonate (CaCO3), typically driven by CO2 loss as spring waters emerge or as carbonate-rich waters drip and flow within caves. These processes…

Introduction Transform faults are plate-boundary faults defined by dominantly horizontal, strike-slip motion between adjacent tectonic plates; unlike generic strike-slip faults, transform faults specifically mark the boundary between plates. They end where they intersect another plate margin, terminating at one of three junction types: another transform, a spreading ridge (divergent boundary), or a subduction zone. Most…

The Timor Plate is a small tectonic microplate in Southeast Asia that underlies the island of Timor and nearby islets, forming an independent crustal block within a tightly interleaved regional plate system. Its southern margin is dominated by a subduction interface where the Australian Plate dives beneath Timor, a convergent contact responsible for north‑directed convergence,…

Tidal triggering of earthquakes posits that the gravitationally driven deformation of the Earth—principally arising from the relative geometry of the Sun, Moon and Earth (syzygy)—can modulate stress on faults that are already close to failure and thereby advance or delay seismic slip. Tidal effects act through two primary pathways: direct elastic deformation of the crust…

Introduction A thunderstorm is a convective weather system marked by lightning and thunder and is typically rooted in towering cumulonimbus clouds. These clouds frequently exhibit extreme vertical extent—often exceeding 20 km—which supports vigorous updraughts and long fall distances for hydrometeors. Initiation generally requires rapid ascent of warm, moisture‑rich air, commonly along frontal boundaries or other…

Introduction Thrust (contractional) tectonics is the branch of structural geology concerned with the structures and kinematics that arise when the lithosphere experiences lateral shortening and concomitant vertical thickening. It describes the formation and evolution of thrust faults, folds and related features that accommodate crustal shortening and is the dominant deformational style at convergent plate boundaries….

Introduction A thermal column (thermal) is a vertical convective current in the lower atmosphere in which relatively warm, buoyant air ascends from the surface, carrying sensible heat upward. Thermals arise from spatial variations in solar heating of the ground: patches that warm more strongly heat the air above them, producing a density deficit that induces…

The Tethys Ocean (Greek: Τηθύς, Tēthús; often anglicized Tethys) was a major Mesozoic–early to mid‑Cenozoic seaway that played a central role in the palaeogeography of Eurasia and adjacent continents. Functioning as the principal marine basin between Laurasia and Gondwana during the early Mesozoic, it constituted a primary conduit for oceanic circulation and biogeographic interchange and…

Introduction Terrain, or topographical relief, describes the form and vertical dimension of the Earth’s surface—from the Latin terra—and is commonly characterized by elevation, slope gradient and aspect. Variations in relief govern the routing and storage of surface water and, when considered at larger scales, can modulate atmospheric circulation and local climate patterns. Contemporary assessment of…

Surface waves are wave modes in which energy is confined to and propagates along the boundary between two distinct media rather than through a homogeneous volume; their behavior is set by the boundary conditions and contrasts in material properties at that interface. Mechanically, this class includes gravity-driven surface waves at the liquid–air boundary—the familiar waves…

Introduction Surface tension is the propensity of a liquid surface at equilibrium to contract and thereby minimize area, producing macroscopic behaviour akin to a stretched elastic membrane; this effect permits some objects denser than the liquid (for example razor blades or water‑striding insects) to remain supported without significant immersion. Microscopically, the phenomenon originates at the…

Introduction A supercontinent is ordinarily defined as the amalgamation of most or all continental blocks or cratons into a single, contiguous landmass; an operational threshold commonly applied requires about 75% or more of the contemporaneous continental crust to be joined, although broader definitions accept any major reaggregation of formerly dispersed continents. Such large-scale assemblies arise…

Introduction The Sunda Plate is a minor tectonic plate in the Eastern Hemisphere that straddles the equator and constitutes the principal lithospheric foundation for much of Southeast Asia. Its geographic and geologic role is central to the arrangement of continental fragments and island arcs across the equatorial sector of the region. Although traditionally considered a…

Introduction The Sun is the central star of the Solar System: a nearly spherical, massive body of hot plasma whose core sustains long‑term nuclear fusion. Classified as a G2V main‑sequence star (commonly called a “yellow dwarf” in informal usage), its integrated emission appears essentially white, while its photospheric radiation is dominated by visible and infrared…

Introduction Submersion denotes a recurrent, often sustainable phase of coastal change in which sediment is transferred from the exposed beach into the submerged nearshore and later returned to rebuild the dry-beach profile. Conceptually the process separates into two morphological domains: the subaerial beach (berms, foreshore and other dry-sand features visible to users) and the subaqueous…

Introduction A submarine earthquake is a seismic rupture that initiates within the seafloor of a body of water—most commonly an ocean—and is the principal source of tsunamis. The energy released by such events is quantified by moment magnitude, while observed effects on people and built systems are described using intensity scales such as the Mercalli…

Introduction Subduction occurs at convergent plate boundaries where oceanic—and occasionally fragments of continental—lithosphere descends into the mantle, forming a tectonic interface (the subduction zone) and a surface arc–trench complex. The process is driven principally by a density contrast: cold, rigid oceanic lithosphere is denser than the underlying asthenosphere, so once down‑faulting begins the slab largely…

A strand plain is a broad, shore‑parallel sand belt directly attached to the mainland whose surface is dominated by well‑defined, parallel or semi‑parallel sand ridges separated by shallow swales. This ridge‑and‑swale morphology is characteristic of shoreface accretionary systems and records repeated episodes of lateral accretion, migration and episodic reworking by storms and normal wave climates….

Introduction Star formation is the process by which localized over-densities within molecular clouds of the interstellar medium collapse under gravity to produce new stars. Giant molecular clouds act as the principal reservoirs of the cold gas and dust from which collapse is initiated; the balance among cooling, turbulent motions, magnetic support and self-gravity determines whether…

The Sphinx water‑erosion hypothesis is a minority geological claim that reads the pattern of weathering on the Great Sphinx and its surrounding quarry walls as the product of prolonged precipitation and fluvial action, and from that inference argues for a Predynastic or otherwise much earlier construction date than conventionally accepted. Advocates such as John Anthony…

The South Sandwich plate (or Sandwich plate) is a small oceanic microplate located south of the South American plate in the Southern Ocean; the volcanic South Sandwich Islands are situated on this microplate. It is flanked by three larger plates: the South American plate to the east (which subducts beneath the microplate), the Antarctic plate…

Introduction The South Bismarck Plate is a small lithospheric block beneath the southern Bismarck Sea in the southwestern Pacific. It incorporates fragments of continental and island crust, most notably the eastern sector of New Guinea and the island of New Britain, which together constitute the plate’s principal surface expression. Tectonically active, the plate experiences frequent…

The South American plate encompasses the continent of South America and an extensive sector of the adjacent Atlantic seafloor, extending eastward to its divergent contact with the African plate and forming the southern segment of the Mid‑Atlantic Ridge. At its eastern margin this spreading boundary records continuous seafloor formation as the South American plate moves…

The Somali Plate is a minor tectonic plate in the Eastern Hemisphere whose domain straddles the Equator and comprises continental crust, rifted continental margins and adjoining oceanic seafloor along Africa’s eastern flank. Roughly centered on Madagascar, it includes portions of the western Indian Ocean and approximately half of Africa’s eastern coastline; its northern limit extends…

Solifluction denotes a class of slow, gravity-driven downslope movements of soil and loose surface material that are primarily set in motion by recurrent freeze–thaw activity. Repeated freezing and thawing alternately lift, sort and lubricate the uppermost, fine-grained horizon, producing incremental displacement of regolith on gentle to moderate slopes. This process yields a range of surface…

Introduction The Solar System is the gravitationally bound ensemble composed of the Sun and all bodies that orbit it. It formed roughly 4.6 billion years ago when a dense portion of a molecular cloud collapsed to produce the Sun and a surrounding protoplanetary disc from which planets, dwarf planets, moons and smaller bodies accreted. The…

Soil science systematically investigates soil as a critical near-surface natural resource, integrating the processes that create soils, their classification and spatial representation, and the physical, chemical, biological and fertility attributes that determine how soils can be used and managed. Central to the discipline are two complementary perspectives: pedology, which concentrates on pedogenesis, morphology, mineralogical and…

Introduction — Soil horizons A soil horizon is a recognisable, laterally extensive layer within a soil profile, arranged approximately parallel to the ground surface and distinguishable in a cross‑section by measurable differences in physical, chemical or biological properties from adjacent layers. The most commonly used field criteria for delimiting horizons are physical attributes—particularly colour and…

Pedogenesis denotes the suite of physical, chemical and biological processes that convert parent material into soil through interactions among local setting, environmental conditions, and temporal history. These biogeochemical mechanisms both construct and degrade internal order within the developing soil, producing anisotropy—systematic directional and spatial contrasts in properties—as constituents are translocated, transformed, accumulated, or lost over…

Introduction Soil erosion denotes the removal of the upper, nutrient-rich soil horizon by dynamic physical and biological processes, resulting in degradation of the medium that sustains plant growth and soil ecosystem functions. A range of agents produces distinct forms of erosion: flowing water, glaciers and snowmelt, wind (aeolian processes), biotic activity by animals and plants,…

Introduction Sociocultural evolution denotes a family of theoretical approaches in sociobiology and cultural evolution concerned with how societies and cultures transform through time. Beyond narratives of progressive complexity, the concept encompasses reductions in complexity (degeneration), branching diversification without net complexity change (cladogenesis), and qualitative reorganization of social structures. In essence, sociocultural evolution analyzes the processes…

Introduction Slow earthquakes (or silent earthquakes) are fault-slip events that release seismic energy over durations of hours to months, in contrast to ordinary earthquakes whose main energy discharge occurs in seconds to minutes. Initially recognized through long‑term strain measurements, many slow events are now known to produce measurable seismic signals—most notably tremor—when continuous seismometer records…