Maharashtra HSC GFC key terms

The outermost solid shell of the Earth, ranging from about 5 km thick under oceans to about 70 km under mountain ranges. It is composed of lighter silicate rocks and floats on the denser mantle beneath.

The thick silicate layer between the crust and the core, extending to about 2,900 km depth. Slow convection currents within it are the driving force behind the movement of tectonic plates.

The rigid outer shell of the Earth made up of the crust and the uppermost part of the mantle. It is broken into separate plates that move over the softer layer below.

The hot, partially molten layer of the upper mantle beneath the lithosphere. Its plastic, slowly flowing nature allows the rigid plates above it to slide and shift.

The theory explaining that the Earth's lithosphere is divided into large plates that move relative to one another. Their collisions, separations and sliding cause earthquakes, volcanoes and mountain building.

A plate margin where two plates move toward each other. One plate may be forced beneath the other, producing deep ocean trenches, volcanic arcs and fold mountains.

A plate margin where two plates move apart and new crust is formed from rising magma. Mid-ocean ridges and rift valleys are typical features of such boundaries.

The process in which a denser oceanic plate sinks beneath a lighter continental or oceanic plate at a convergent margin. It generates deep trenches, earthquakes and volcanic activity.

The gradual creation of new oceanic crust at mid-ocean ridges as magma rises and solidifies, pushing older crust outward on both sides. It provides evidence for continental drift.

The focus is the point inside the Earth where an earthquake originates; the epicentre is the point on the surface directly above it. Surface damage is usually greatest near the epicentre.

Energy released by an earthquake that travels through the Earth as vibrations. P-waves and S-waves are body waves, while surface waves cause most of the shaking and damage.

A naturally occurring, inorganic solid with a definite chemical composition and an ordered internal atomic structure. Minerals are identified by properties such as hardness, cleavage, lustre and colour.

A relative scale from 1 (talc) to 10 (diamond) ranking minerals by their resistance to scratching. A mineral can scratch any mineral lower on the scale but not those higher.

A solid aggregate of one or more minerals, or of organic material such as coal. Rocks are grouped as igneous, sedimentary or metamorphic according to how they formed.

Rock formed by the cooling and solidification of magma or lava. Intrusive types such as granite cool slowly underground and are coarse-grained; extrusive types such as basalt cool quickly and are fine-grained.

Rock formed from compacted and cemented sediments, or from chemical precipitation and organic remains. Layers called strata and the presence of fossils are characteristic features.

Rock that has been changed in form by high heat, pressure or chemically active fluids while remaining solid. Examples include marble from limestone and slate from shale.

The continuous series of processes by which rocks are formed, broken down and reformed over geological time. Weathering, erosion, deposition, burial, heat and melting link the three rock types.

The breakdown of rocks in place by physical, chemical or biological processes. Freeze-thaw action, solution and root wedging are common agents; the broken material later becomes soil.

The removal and transport of weathered rock material by moving water, wind, ice or gravity. It shapes valleys, deltas and dunes and is distinct from weathering, which does not involve transport.

The laying down of eroded sediment when the transporting agent loses energy, such as a river slowing on entering a plain. Deposited layers may later harden into sedimentary rock.

A landform created by the action of running water, such as a V-shaped valley, meander, oxbow lake, waterfall or alluvial fan. River processes erode, transport and deposit material along the course.

A vertical section through soil showing its distinct horizons from surface litter down to bedrock. The O, A, B and C horizons differ in organic content, colour and texture.

Dark, decomposed organic matter in the upper soil layer formed from plant and animal remains. It improves water retention, aeration and nutrient supply and supports forest growth.

A classification of forests based on climate, rainfall, temperature and dominant species, such as tropical evergreen, moist deciduous, dry deciduous and thorn forest. India's forest types follow Champion and Seth's scheme.

The upper layer of a forest formed by the crowns of tall trees. It intercepts sunlight and rainfall and creates distinct microclimates and habitats for many species.

The layer of shrubs, saplings and small trees growing between the forest floor and the canopy. It provides food, cover and nesting sites for wildlife and influences regeneration.

Dead leaves, twigs and other plant material lying on the forest floor. Its decomposition by microbes and detritivores returns nutrients to the soil and builds humus.

The science and practice of establishing, tending and harvesting forest crops to meet specific objectives. It includes regeneration methods, thinning, pruning and rotation planning.

The renewal of a forest from seed, coppice or root suckers without deliberate planting. It depends on seed trees, favourable soil and protection from grazing and fire.

The removal of selected trees from a stand to reduce competition and favour the growth of remaining trees. It improves timber quality, light penetration and stand health.

The planned period between the establishment of a forest crop and its final felling. Rotation length depends on the species and the products desired, such as poles or sawlogs.

Wood from felled trees suitable for construction, furniture and other structural uses. Its quality depends on species, grain, moisture content and freedom from defects.

Goods other than industrial timber obtained from forests, such as honey, gum, resin, bamboo, fodder, medicinal plants and fruits. These support rural livelihoods and local economies.

A category of forest products including tendu leaves, bamboo, honey, wax, gums and medicinal herbs collected by local communities. It is a major source of income for forest-dependent households.

A region with exceptionally high species richness and endemism that has lost a large part of its original habitat. The Western Ghats and the Himalaya are recognised hotspots in India.

A species found naturally only in a particular, often small, geographic area. Endemics are highly vulnerable to habitat loss and are priority targets for conservation.

A legally designated region managed mainly for biodiversity conservation, such as a national park, wildlife sanctuary or biosphere reserve. Human activities within it are regulated or restricted.

The presence in the atmosphere of substances or forms of energy at concentrations harmful to health, ecosystems or materials. Major pollutants include particulate matter, sulphur dioxide and nitrogen oxides.

The warming of the Earth's surface as certain atmospheric gases trap outgoing infrared radiation. Human emissions of carbon dioxide and methane are intensifying this natural process.

A reservoir such as a forest, soil or ocean that absorbs and stores more carbon than it releases. Forests act as sinks through photosynthesis and long-term storage in wood and soil.

Development that meets present needs without compromising the ability of future generations to meet theirs. It balances economic growth, social equity and environmental protection.

A participatory approach in which forest departments and local communities jointly protect and manage degraded forests in return for a share of benefits. It is widely practised in India.

A field technique for sampling vegetation by recording species and counts within a square plot of known area. Repeated quadrats give estimates of density, frequency and abundance.

A line or narrow strip laid across a habitat along which observations are recorded at intervals. It is used to study changes in vegetation or wildlife across a landscape.

A collection of dried, pressed and labelled plant specimens kept for identification, reference and research. Each specimen records the species name, location and date of collection.