Kerala Plus Two Geology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Moho discontinuity

The seismic boundary between the Earth's crust and mantle, marked by a sharp increase in P-wave and S-wave velocity at roughly 30 to 35 km beneath continents and 7 to 10 km beneath oceans.

Isostasy

The state of gravitational balance in which the lithosphere floats on the denser asthenosphere, so that thicker or denser crust sinks deeper and thinner or lighter crust rises higher.

Sea-floor spreading

The process by which new oceanic crust forms at mid-ocean ridges as magma rises, cools, and moves laterally away from the ridge, producing symmetrical magnetic stripes and increasing crustal age with distance.

Mohs hardness scale

A relative scale from 1 (talc) to 10 (diamond) ranking minerals by resistance to scratching, where each mineral scratches those below it and is scratched by those above it.

Silicate tetrahedron

The SiO4^4- structural unit of one silicon atom bonded to four oxygen atoms, which links in various ways to form the framework of all silicate minerals.

Bowen's reaction series

A sequence describing crystallisation order of minerals from cooling magma, from high-temperature olivine, pyroxene, and amphibole to low-temperature muscovite and quartz.

Polymorphism

The phenomenon in which two or more minerals share the same chemical composition but differ in crystal structure and physical properties, such as diamond and graphite.

Phaneritic texture

An igneous texture in which individual mineral grains are coarse enough to be seen with the unaided eye, typically indicating slow cooling and crystallisation at depth.

Foliation

A planar arrangement of platy or elongate minerals in metamorphic rock, produced by directed stress during recrystallisation and giving rocks such as schist and gneiss their layered appearance.

Graded bedding

A sedimentary structure in which grain size decreases upward within a single bed, typically deposited by a waning turbidity current and useful for determining way-up.

Protolith

The original, pre-metamorphic parent rock from which a metamorphic rock formed, for example limestone for marble or sandstone for quartzite.

Anticline

A fold with the oldest rocks in its core and limbs dipping away from the axis, typically formed by compressional stress and often forming a topographic ridge.

Normal fault

A fault formed under tension in which the hanging wall moves down relative to the footwall, commonly associated with divergent plate boundaries and crustal extension.

Strike and dip

Two measurements describing a planar surface: strike is the compass direction of its horizontal line, and dip is its maximum inclination from horizontal, perpendicular to strike.

Angular unconformity

An erosion surface separating tilted or folded older strata below from younger, near-horizontal strata above, indicating a period of deformation followed by erosion and renewed deposition.

Index fossil

A fossil species with a wide geographic range but a short stratigraphic lifespan, used to correlate and date rock layers across distant regions.

Gondwana

An ancient supercontinent comprising India, Africa, South America, Australia, Antarctica, and Madagascar, whose breakup shaped the present southern continents and Indian Ocean.

K-Pg boundary

The stratigraphic horizon about 66 million years ago marking the end of the Cretaceous, associated with a global iridium anomaly, mass extinction of dinosaurs, and Deccan volcanism.

Charnockite

A coarse-grained granulite-facies rock containing hypersthene and orthoclase, common in the Southern Granulite Terrain and designated as the state rock of Kerala.

Laterite

A residual, iron and aluminium rich soil or rock formed by intense tropical chemical weathering and leaching of silica, widespread across Kerala and used as building material.

Warkalli beds

Tertiary sedimentary strata of Kerala containing sandstone, clay, and lignite with plant fossils, exposed along the coastal cliffs and representing a former coastal depositional environment.

Deccan Traps

A vast flood basalt province of peninsular India erupted around 66 million years ago, covering about 500,000 square kilometres and linked to the Réunion hotspot.

Ore grade

The concentration of a valuable metal in an ore deposit, expressed as a percentage or grams per tonne, which determines whether extraction is economically viable.

Placer deposit

A concentration of heavy, resistant minerals such as monazite, ilmenite, or gold formed by water or wind sorting of sediments, common in Kerala's beach sands.

Gangue

The unwanted, non-economic minerals associated with an ore body, which must be separated from the valuable minerals during beneficiation and processing.

Aquifer

A geological formation or rock unit that stores and transmits groundwater in sufficient quantity to supply wells or springs, such as laterite or fractured crystalline rock.

Darcy's law

The relationship Q = K i A, stating that groundwater discharge through a porous medium equals hydraulic conductivity times hydraulic gradient times cross-sectional area.

Ghyben-Herzberg relation

The principle that in a coastal aquifer the freshwater lens extends below sea level about forty times the height of the water table above sea level, guiding safe pumping limits.

Eutrophication

The enrichment of a water body with nutrients, especially nitrates and phosphates, causing excessive algal growth, oxygen depletion, and deterioration of water quality.

Brunton compass

A geological instrument combining a compass, clinometer, and level, used in the field to measure the strike and dip of rock layers and the bearing of geological features.

Thin section

A rock slice ground to about 0.03 mm thickness and mounted on a glass slide, allowing mineral identification by optical properties under a polarising microscope.

Contour interval

The vertical distance between successive contour lines on a topographic map, which indicates the map's relief detail and helps interpret slope and landform shape.