One question at a time. Build your WBBSE Madhyamik Geography understanding.
First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.
Continue in the practice tool above to load more questions, 50 at a time.
The asthenosphere is the partly molten, plastic layer of the upper mantle lying beneath the rigid lithosphere. Its plasticity allows the overlying plates to drift slowly. The other layers named here lie either deeper inside the Earth or in the atmosphere, so they cannot serve as the plate-bearing zone.
The Indian plate drifted northwards and collided with the Eurasian plate, folding the sediments of the Tethys Sea into the Himalayan ranges. This is a convergent boundary between two continental plates. The other plates listed lie far from the Himalayan belt and are not involved in its uplift.
An oceanic trench marks a subduction zone where a denser plate descends into the mantle, producing an extremely deep and narrow trough. The Mariana Trench is the classic example. Ridges, shelves and abyssal plains form under different processes and are not subduction features.
The Andes are young fold mountains raised along a convergent plate margin where the Nazca plate subducts beneath South America. The Vindhya, Aravalli and Satpura ranges of peninsular India are old block or residual ranges, not young fold mountains. Hence only the Andes fit the fold-mountain category.
A seismograph detects ground vibrations and draws a seismogram, from which the earthquake's magnitude and duration are read. Barometers measure air pressure, hygrometers measure humidity and anemometers measure wind speed. Only the seismograph is designed for seismic waves.
The focus, or hypocentre, is the point inside the Earth where the earthquake originates, and the point directly above it on the surface is the epicentre. Seismic waves spread outwards from the focus and are usually strongest near the epicentre. Isoseismal lines join places of equal shaking intensity.
A barometer measures the weight of the air column and thus atmospheric pressure, usually in millibars or hectopascals. Pressure differences drive winds and influence weather systems. Thermometers, wind vanes and rain gauges record temperature, wind direction and rainfall respectively.
The Equator is the great circle of latitude at 0 degrees and splits the globe into northern and southern halves. The tropics lie at 23.5 degrees north and south, while the Prime Meridian is a line of longitude. Only the Equator performs this hemispheric division.
The overhead sun at the Tropic of Cancer occurs around 21 June, the summer solstice, when the Northern Hemisphere receives its most direct and longest-lasting insolation. This is the middle of northern summer. The Southern Hemisphere then has its winter, and equinoctial seasons occur at other dates.
On 21 June the sun is overhead at the Tropic of Cancer, and all places in the Northern Hemisphere, including 30 degrees north, receive the longest daylight of the year. The March and September equinoxes give roughly equal day and night. The December solstice gives the shortest day in the north.
Trade winds blow from the subtropical highs near 30 degrees towards the equatorial low, and the Coriolis force turns them right in the Northern Hemisphere, giving the north-east trades. Westerlies blow poleward from the same highs, and polar easterlies blow from the poles. Monsoons are seasonal reversals tied to land-sea heating.
The equatorial trough, or doldrums, is a belt of ascending air, weak surface winds and heavy convectional rain. Sailing ships were often becalmed there, hence the name. The horse latitudes are the subtropical calms, while the roaring forties and furious fifties are stormy westerly belts of the southern oceans.
Relative humidity expresses the actual vapour content as a percentage of the maximum the air could hold at that temperature. Cool air holds less vapour, so the same vapour content gives a higher percentage, approaching saturation. Warm, dry air and strong winds lower relative humidity rather than raise it.
When moist air is forced up a mountain slope it cools, condenses and releases rain on the windward side, leaving a rain shadow on the leeward side. This relief-driven mechanism is orographic rainfall. Frontal and convectional rainfall arise from other processes.
After crossing the crest, air descends, compresses and warms adiabatically, so its relative humidity drops and cloud formation is suppressed. Most of its moisture was already lost on the windward slope. The result is a dry leeward belt, as seen in the Deccan interior behind the Western Ghats.
The troposphere is the lowest atmospheric layer, containing most of the water vapour and dust and showing a steady fall of temperature with height. Clouds, rain, storms and winds are confined largely to it. The higher layers are too dry and stable for ordinary weather.
Ozone is concentrated in the stratosphere, roughly 15 to 35 kilometres above the surface, where it absorbs ultraviolet rays and protects life. This absorption also warms the stratosphere. The troposphere, mesosphere and exosphere contain only traces of ozone.
The Coriolis effect arises from the Earth's rotation, which gives different linear speeds at different latitudes and bends moving air to the right in the north and to the left in the south. It influences wind direction and cyclone rotation. The other effects relate to radiation balance or local winds.
The Foehn is a warm, dry descending wind on the leeward side of the Alps, caused by adiabatic warming as air descends. It melts snow and hastens crop ripening in Alpine valleys. The Mistral, Sirocco and Bora are cold or hot winds of other regions with different origins.
Condensation is the change of water vapour into liquid water when air cools to its dew point, forming dew, fog and cloud droplets. Evaporation and transpiration add vapour to the air, while infiltration moves water into the soil. Only condensation produces droplets from vapour.
Evapotranspiration combines evaporation from soil and water bodies with transpiration from vegetation, returning moisture to the atmosphere. Run-off and percolation move water along or into the ground instead. Precipitation is the opposite flux, bringing water down from the atmosphere.
In a strongly meandering river, deposition narrows the neck of a loop until the river takes a straighter course, leaving the abandoned loop as a crescent-shaped ox-bow lake. Glacial, karst and wind processes create different landforms. The ox-bow is thus a fluvial depositional feature.
Erosion depends on the kinetic energy of flowing water, which rises with velocity, and on the abrasive tools carried as load. Fast water with coarse sediment can abrade and quarry the bed and banks effectively. Slow, shallow or low-gradient conditions reduce erosive capacity.
In hot deserts, sparse vegetation and dry, loose surface material allow wind to deflate, abrade and transport sand, shaping yardangs, zeugen and dunes. Rivers are mostly ephemeral and glaciers and waves are absent from interior deserts. Wind is therefore the dominant erosional agent.
Sand-laden wind is most effective close to the ground, so it erodes the lower part of a rock faster than the top, leaving a narrow base and a broad cap like a mushroom. This is a form of differential abrasion. Solution and frost action belong to humid and cold environments.
Seismic waves speed up sharply at the base of the crust because the rock below is denser and more rigid. This boundary is named the Mohorovicic discontinuity after the seismologist who detected it. It lies roughly 5 to 10 km below the ocean floor and 30 to 70 km below the continents.
Extrusive igneous rocks form when magma reaches the surface as lava and cools quickly in the open air. Rapid cooling produces fine crystals, which is why basalt has a smooth, dense texture. Intrusive rocks, by contrast, crystallise slowly underground and are coarse-grained.
Compression of the crust can bend layered rocks into arches and troughs. An upward arch is an anticline, and because the layers are pushed up, the oldest beds appear in its core. A downward trough is a syncline, where the youngest beds lie in the centre.
Hydraulic action is the direct force of flowing water forcing air into cracks and prising rock fragments loose. It works alongside abrasion, attrition and solution to erode the channel. It is strongest where the current is fast, such as in rapids and waterfalls.
The Pacific Ocean covers roughly one-third of the Earth's surface and contains the deepest known trench, the Mariana Trench. Its vast area and average depth make it the largest ocean basin. The Atlantic, Indian and Arctic oceans are all considerably smaller.
An isthmus is a land bridge between two larger land areas, such as the Isthmus of Panama linking North and South America. It separates water bodies while connecting land. A strait is the opposite feature, a narrow water passage between two land areas.
The normal lapse rate in the troposphere averages about 6.5 degrees Celsius per kilometre of ascent. This is why hill stations are cooler than the plains at the same latitude. The rate varies with humidity and season but this figure is the standard average used in geography.
Map isolines are named by the quantity they connect. An isohyet joins places receiving equal rainfall, which helps show the distribution of precipitation over a region. Isobars, isotherms and isohels refer to pressure, temperature and sunshine respectively.
On 21 December the sun is overhead at the Tropic of Capricorn, so the Southern Hemisphere has its longest day and the Northern Hemisphere its shortest. A place at 20 degrees south therefore experiences its longest day then, not its shortest. Its shortest day falls on 21 June, when the sun is overhead at the Tropic of Cancer and the Southern Hemisphere is tilted away from the sun.
A cyclone is a low-pressure system, so air flows inwards towards the centre to fill the pressure deficit. The Coriolis force deflects this inward flow to the right in the Northern Hemisphere, giving an anticlockwise spiral. In the Southern Hemisphere the same system turns clockwise.
Land heats and cools faster than water because of the difference in specific heat. During the day the land becomes warmer, air rises over it, and cooler air flows in from the sea as a sea breeze. At night the pattern reverses to form a land breeze.
Air that has risen at the Equator loses its moisture and descends around 30 degrees latitude. As it sinks it warms and its relative humidity falls, so clouds rarely form and rainfall is scarce. This subsidence is why many of the world's great deserts lie near the tropics of Cancer and Capricorn.
When a steep stream reaches flatter ground its velocity drops abruptly and it can no longer carry its coarse load. The material is dumped in a fan-shaped spread at the base of the slope. Deltas form where rivers enter standing water such as a lake or sea, not at a mountain foot.
Moraines are ridges of unsorted rock debris dropped by a glacier as it melts and retreats. They are depositional features built up from material the ice carried. Cirques, aretes and hanging valleys are all shaped by glacial erosion.
At the Equator the north-east and south-east trade winds meet in the Inter-Tropical Convergence Zone. The warm, moist air is forced to rise, cools adiabatically and condenses into towering cumulonimbus clouds. This produces convectional rain almost daily, giving the equatorial belt its year-round wetness.
At 6.5 degrees Celsius per kilometre, a rise of 2,000 metres gives a cooling of about 13 degrees. Subtracting this from 30 degrees Celsius leaves roughly 17 degrees Celsius. This calculation explains why highlands are noticeably cooler than lowlands at the same latitude.
Intense rainfall in the humid tropics washes soluble bases and silica downwards, leaving iron and aluminium oxides behind. These give laterite soils their red colour and low fertility. Chernozems, podzols and peats form in very different climatic settings.
Discharge equals cross-sectional area multiplied by velocity, so velocity is discharge divided by area. Dividing 40 by 20 gives 2 metres per second. This relation helps explain why a river speeds up where its channel narrows.
In summer the low-pressure area over north-west India draws moist air from the Indian Ocean. These south-west monsoon winds pick up moisture over the sea and bring heavy rain to the windward side of the Western Ghats. The winter monsoon, by contrast, blows from the north-east and is largely dry over most of India.
A tsunami is generated when a submarine earthquake displaces a huge volume of ocean water, sending long waves across the sea at high speed. The waves grow tall as they reach shallow coastal water and can cause severe destruction. Tidal bores, storm surges and spring tides have different causes.
One degree of latitude is about 111 kilometres on the Earth's surface. The two places differ by 30 degrees of latitude, so the distance is roughly 30 multiplied by 111, giving about 3,330 kilometres. Longitude does not affect this calculation because both places share the same meridian.
When warm, moist air moves over a cold surface, the lowest layer of air is chilled from below. This makes the air mass stable, since the colder dense air lies beneath warmer air. Moisture condenses readily in the cooled lower layer, giving fog, stratus cloud and drizzle.
Water has a higher specific heat than land, so the sea warms and releases heat to the air more slowly. The coastal station's air temperature therefore lags behind that of the inland station, which responds quickly to solar heating. This lag is a key feature of maritime compared with continental temperature regimes.
A river's competence, its ability to move coarse particles, depends largely on velocity, which falls as the gradient flattens. In the lower course the gentler slope reduces velocity, so only finer material can be carried in suspension. Coarse bed load is therefore deposited upstream.
Moist air forced to rise over the windward slope cools and condenses, giving heavy orographic rain and lush vegetation. Once over the crest the air descends, warms and dries, leaving the leeward side in a rain shadow. The windward range therefore receives more rain on its windward slope than the leeward range.