Maharashtra HSC GFC flashcards

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

Lithosphere

The rigid outer shell of Earth comprising the crust and uppermost mantle, roughly 100 km thick, broken into tectonic plates that move over the plastic asthenosphere.

S-wave shadow zone

A zone between about 103 and 142 degrees from an earthquake epicentre where shear waves are not recorded, proving that the outer core is liquid.

Sea-floor spreading

Hess's hypothesis that new oceanic crust forms at mid-ocean ridges and moves away symmetrically, recorded as mirror-image magnetic stripes and increasing sea-floor age away from ridges.

Slab pull

The dominant plate-driving force in which dense subducting oceanic lithosphere sinks into the mantle at convergent margins and drags the rest of the plate behind it.

Mohs hardness scale

A ten-point relative hardness scale from talc (1) to diamond (10), in which a mineral scratches softer ones; quartz at 7 scratches glass and fingernail is about 2.5.

Porphyritic texture

An igneous texture with large crystals set in a finer groundmass, indicating two cooling stages: slow cooling at depth followed by faster cooling near the surface.

Foliation

Parallel alignment of platy minerals in metamorphic rocks under directed pressure, producing the sequence slate, phyllite, schist and gneiss with increasing metamorphic grade.

Rock cycle

The set of processes by which igneous, sedimentary and metamorphic rocks are transformed into one another through weathering, erosion, deposition, compaction, heat, pressure and melting.

Carbonation weathering

Chemical weathering in which carbonic acid dissolves limestone and other carbonate rocks, producing soluble bicarbonates and forming karst features such as caves, sinkholes and stalactites.

Oxbow lake

A crescent-shaped water body formed when a strongly meandering river cuts across a narrow neck of land, abandoning a loop of the old channel on the floodplain.

Barchan dune

A crescent-shaped sand dune formed by wind, with a gentle windward slope, a steep leeward slip face, and horns pointing downwind where sand supply is limited.

Cirque

A bowl-shaped hollow eroded at the head of a glacier by rotational ice movement, often containing a tarn and flanked by steep headwalls and arêtes.

Champion and Seth classification

The standard Indian forest type classification of 1968, grouping forests into 16 major types based mainly on climate, rainfall and altitude, from wet evergreen to alpine.

Importance Value Index

A phytosociological measure calculated as relative density plus relative frequency plus relative dominance, summing to 300 for all species in a community sample.

Mangrove adaptations

Special features of salt-tolerant coastal trees, including pneumatophores for aeration, viviparous germination, salt-excluding or excreting leaves, and stilt roots for stability in mud.

Krummholz

Stunted, wind-deformed trees and shrubs at the upper treeline in alpine and subalpine zones, where low temperature and strong wind limit normal upright tree growth.

Shelterwood system

A silvicultural system in which mature trees are removed in a series of cuttings so that natural regeneration becomes established under partial shade before final felling.

Thinning

A tending operation that removes selected trees from a stand to reduce competition, improving growth, health and quality of the retained crop trees.

Taungya system

An agroforestry practice in which farmers raise agricultural crops between newly planted tree seedlings, weeding and tending the trees until the canopy closes.

Working plan

A written, legally sanctioned scheme for a forest division that prescribes felling, regeneration, protection and yield regulation over a defined period to ensure sustained yield.

Heartwood

The darker, non-conducting inner wood of a mature tree, made of dead cells filled with extractives, generally more durable and resistant to decay than sapwood.

Tendu leaves

Leaves of Diospyros melanoxylon, an important Indian non-timber forest produce harvested seasonally and used mainly for wrapping bidis and for local trade.

Oleoresin

A natural secretion tapped from conifers such as chir pine, which on distillation yields rosin and turpentine used in paints, adhesives and pharmaceuticals.

Biodiversity hotspot

A region with exceptionally high endemic species richness that has lost a large part of its original habitat; India contains parts of four such global hotspots.

Keystone species

A species whose removal causes disproportionate change to the ecosystem, such as a fig tree providing fruit for many animals or a predator controlling herbivore numbers.

Ex-situ conservation

Conservation of biodiversity outside natural habitats, through zoos, botanical gardens, seed banks, gene banks and cryopreservation, complementing protected areas.

Eutrophication

Nutrient enrichment of water bodies, mainly by nitrogen and phosphorus, causing algal blooms, oxygen depletion, fish kills and loss of aquatic biodiversity.

Biological oxygen demand

The amount of dissolved oxygen consumed by microorganisms decomposing organic matter in a water sample over a set period, used as an indicator of organic pollution.

Paris Agreement

A 2015 global climate treaty under the UNFCCC in which countries submit nationally determined contributions to keep warming well below 2 degrees Celsius, aiming for 1.5.

Brundtland definition

The 1987 formulation that sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs.

Watershed management

Integrated treatment of a catchment using contour bunding, check dams, percolation tanks and afforestation to conserve soil and water and recharge groundwater.

Six-figure grid reference

A map location given as three digits eastings followed by three digits northings, locating a point within a 100-metre square on a typical topographic map.