Category: Geography

The Woodlark Plate is a small, nearly triangular tectonic block named for the Woodlark region, located immediately east of New Guinea and concentrated in the northern sector of the Woodlark Basin. Its spatial extent overlaps with, but does not encompass, the entire basin, reflecting a localized plate that occupies only the basin’s northern half. The…

Introduction Weathering denotes the in situ breakdown and alteration of rocks, soils, minerals, wood and anthropogenic materials by environmental agents—principally water, atmospheric gases (notably O2 and CO2), solar radiation and biological activity—and is distinct from erosion in that weathering entails negligible transport of material while erosion involves its movement by water, ice, wind, waves or…

Introduction — Weathering Weathering denotes the on-site breakdown of rocks, minerals, soils, wood and man-made materials through interaction with water, atmospheric gases, sunlight and living organisms. The qualifier “in situ” emphasizes that weathering alters materials largely without substantial transport, distinguishing it from erosion, which removes and conveys disintegrated matter by agents such as running water,…

Introduction A wave-cut platform (also termed a shore platform, coastal bench, or wave-cut cliff) is a narrow, nearly level geomorphic surface produced by the erosive action of waves at the base of a sea cliff or along the shoreline of a bay, sea, or lake. It represents the abrasion and undercutting zone where persistent wave…

Introduction — Water vapor Water vapor is the gaseous form of H2O and one of the principal phases of water within Earth’s hydrosphere, distinct from liquid water and solid ice. In the atmosphere it is generated chiefly by evaporation and boiling of liquid water and by sublimation of ice; under typical tropospheric conditions continuous evaporation…

Introduction Earth’s hydrosphere is overwhelmingly saline: oceans and marginal seas, together with saline groundwater and saline endorheic lakes, constitute over 97% of planetary water. Fresh water represents only a small fraction of the total—on the order of 1%—so that the mass ratio of salt water to fresh water is roughly 50:1. Mean ocean salinity is…

A volcano is the surface expression of a subsurface magmatic system: a conduit, vent, or fissure that links a magma reservoir to the exterior and permits the eruption of molten rock, fragmented pyroclasts and magmatic gases. On Earth the spatial pattern of volcanism is primarily governed by plate tectonics. Most volcanic activity is concentrated where…

Introduction Volcano‑tectonic earthquakes are seismic events generated by the emplacement and movement of magma within the crust. As magma intrudes and migrates it perturbs the local stress field and modifies pore pressure, provoking brittle failure or slip on adjacent rock; these ruptures produce measurable seismic waves that record the subsurface magmatic processes. Such events therefore…

Volcanic winter denotes a pronounced fall in global surface temperatures following a large, highly explosive eruption that emits abundant sulfur gases; the principal climatic agent is stratospheric sulfate aerosol, which raises planetary albedo and reduces the solar energy reaching the surface. Sulfur species (chiefly SO2 and H2S) must be lofted into the stratosphere, where they…

Introduction Volcanic rocks are igneous lithologies generated directly by volcanic eruption, incorporating both effusive lava flows and the fragments ejected into the atmosphere during explosive activity. Among these products, ignimbrite records deposition from pyroclastic density currents (pyroclastic flows) and constitutes a principal facies of explosive eruptions. The loose fragments and their reworked accumulations—collectively termed pyroclastics—are…

Introduction A volcanic pipe, or volcanic conduit, is the preserved subsurface channel produced by a violent, deep-sourced eruption that excavates a narrow, high‑velocity pathway for magma and fragmented country rock. As a variety of diatreme, a volcanic pipe commonly appears in the rock record as a deep, steeply tapering cone of brecciated country rock and…

Introduction — Volcanic Explosivity Index (VEI) The Volcanic Explosivity Index (VEI), developed in 1982 by C. G. Newhall and S. Self (USGS), is a semi‑quantitative ordinal scale designed to compare the size and explosiveness of volcanic eruptions and to assist in hazard assessment. Assignment of a VEI integrates measured tephra volume, observed eruption cloud (column)…

Introduction The uvala is a karst landform name that originated as a local toponym across parts of the Dinaric region (Slovenia, Croatia, Bosnia and Herzegovina, Montenegro and Serbia) to denote a closed depression. In geomorphological usage the term designates closed karst basins that are typically larger than individual sinkholes (dolines) and often display irregular, elongated…

Introduction The universe comprises the entirety of space and time and all entities and processes within them—every physical interaction, constant, and form of matter and energy—constituting a single spacetime manifold whose global properties are the object of cosmology. Contemporary cosmology locates the origin of space and time in the Big Bang, dated to 13.787 ±…

Introduction Ultramafic rocks are igneous or meta‑igneous lithologies dominated by dark, iron‑ and magnesium‑rich silicate minerals, typically comprising more than 90% mafic phases. They are chemically distinct from most other igneous rocks by their very low silica contents (SiO2 < 45%), high magnesium abundances (commonly MgO > 18%), elevated FeO, and characteristically low potassium concentrations,…

Introduction This chapter surveys earthquake phenomena by classifying event types, causal mechanisms, observational descriptors, measurement methods, and applied practices that constitute seismology and earthquake-hazard science. The classification distinguishes event sequences (foreshock–mainshock–aftershock), rupture styles and tectonic settings (e.g., blind thrusts, doublets, interplate and intraplate events, megathrusts), special categories defined by triggering or rupture behavior (remotely triggered,…

Introduction A tsunami is a sequence of water waves generated by the sudden displacement of a large volume of water—most commonly in oceans or large lakes. The term derives from the Japanese 津波, literally “harbour wave.” Unlike ordinary wind waves (produced by atmospheric forcing) or tides (driven by lunar and solar gravity), tsunamis result from…

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…