Test: Geography- 8 - UPSC MCQ

Velds lie in the Southern hemisphere, and prairies lie in the Northern Hemisphere.
When Southern hemisphere (Velds) faces the Sun, the Northern Hemisphere comparatively receives lesser insolation.

North-West European Maritime Climate is also called as the British Climate type. The cool temperate western margins are under the influence of the Westerlies all-round the year.
They are the regions of frontal cyclonic activity, i.e. Temperate Cyclones, but these are not the reason for an abnormally mild winter (reason below).

• It is called as North-West European Maritime Climate due to greater oceanic influence.
• The mean annual temperatures are usually between 5° C and 15° C.
• Winters are abnormally mild. This is because of the warming effect brought by warm North Atlantic Drift.
• Sometimes, unusual cold spells are caused by the invasion of cold polar continental air (Polar Vortex) from the interiors.

The tropical rainforest biome has four main characteristics: very high annual rainfall, high average temperatures, nutrient-poor soil, and high levels of biodiversity (species richness).
The soil is nutrient poor because of the heavy rain that leaches the top layer of the soil frequently. Temperature is high because they are largely found in equatorial regions and species richness is high due to abundance of the range of biotic and abiotic factors expressed in the ecosystem.

Taiga, generally referred to in North America as boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of fir, pines, spruces, and larches. The taiga or boreal forest is the world’s largest land biome.

• Dead Zone is an area in water body that contains little or no oxygen (or they are hypoxic) in bottom and near-bottom water.
• Mostly they occur naturally but it can be caused by excessive nutrient pollution from human activities coupled with other factors.
• They are well-known off western coasts of North and South America, off coast of Namibia and off west coast of India in Arabian Sea.
• In recent times, warming of the atmosphere through climate change is predicted to lead expansion of ‘dead zones’ in the ocean.

• The oceans store much more carbon than the atmosphere and the terrestrial biosphere (plants and animals).
• The carbon, however, requires centuries to penetrate into the deep ocean, because the mixing of the oceans is a rather slow.
• However, even more carbon is stored in the lithosphere, i.e. the rocks on the planet, including limestones (calcium carbonate, CaCO₃).

• A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics.
• This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.
• The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean, making the mid-oceanic ridge system the longest mountain range in the world, with a total length of about 60,000 km.
• It is characterised by a central rift system at the crest, a fractionated plateau and flank zone all along its length.
• The rift system at the crest is the zone of intense volcanic activity.

• Ocean vents eject hot, often toxic, fluids and gases into the surrounding seawater. They often mark sites of tectonic activity, and create some of the most hostile habitats on Earth.
• Ocean vents are the product of tectonic activity beneath the ocean floor. Tectonic activity describes the way tectonic plates, giant slabs of Earth’s lithosphere, interact with each other.
• Ocean vents are found in all ocean basins, although they are most abundant around the Pacific Ocean’s “Ring of Fire,” which also includes active earthquake zones, volcanoes, and ocean trenches.
• Ocean vents are primarily found around mid-ocean ridges and volcanic arcs. At both mid-ocean ridges and back-arc basins, the molten magma of Earth’s asthenosphere wells up close to the surface.

Ocean vents are a type of hydrothermal vent. Other types of hydrothermal vents include hot springs, geysers, and fumaroles. As their name indicates, all hydrothermal vents are characterized by water (hydro-) and extremely high temperatures (thermal).

• The location of the thermal equator is not identical to that of the geographic Equator. This is not due to the Level of insolation received in both hemispheres. They are virtually equal.
• What creates the difference is the distribution of land and water that causes changes in the way heat is distributed and transported across the planets.
• Land dominated areas will tend to have a large variation in temperature and a higher average temperature under the same conditions (as compared to a water dominated area).
• Thus, the thermal equator lies a bit north of the geographical equator.

The earth receives almost all of its energy from the sun. The earth in turn radiates back to space the energy received from the sun. As a result, the earth neither warms up nor does it get cooled over a period of time.

The mesosphere lies above the stratosphere, which extends up to a height of 80 km. In this layer, temperature starts decreasing with the increase in altitude and reaches up to minus 100°C at the height of 80 km.
The ionosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Temperature here starts increasing with height.

Annual range of temperature is the difference between mean temperature of the warmest and the coldest months.
The places in the interior of continent do not experience moderating effects of sea. Hence these places have extreme temperature.
Annual precipitation is usually low in the interior areas.

The physiography or relief of India also affects the temperature, air pressure, direction and speed of wind and the amount and distribution of rainfall.

• That many of the areas of the world with high ranges of tides are in the areas of Alaska, Canada, and northern Europe has created a misconception that the range of tide increases with increasing latitude (as one moves farther from the equator and closer to the poles). This is incorrect.
•  Increased tidal ranges in these areas are created by the positions and configurations of the continents in the northern hemisphere. In the higher latitudes of the northern hemisphere, the continents of North America, Europe, and Asia are pressed closer together. This “constriction” of the oceans creates the effect of a higher range of tides. 
•  In the higher latitudes of the southern hemisphere, in the southern tips of South America, southern Africa, Australia, and Antarctica, tidal ranges are not increased. In these areas the continents are not pressed closely together, there is not a “constriction” of the oceans, and the tidal ranges are not increased.

The strong gravitational pull exerted by the sun and the moon on the earth’s surface causes the tides. 
The water of the earth closer to the moon gets pulled under the influence of the moon’s gravitational force and causes high tide. 
The shape of bays and estuaries also can magnify the intensity of tides. Funnel-shaped bays in particular can dramatically alter tidal magnitude. 

• Strong offshore winds can move water away from coastlines, exaggerating low tide exposures. 
• Onshore winds may act to pile up water onto the shoreline, virtually eliminating low tide exposures. 
• High-pressure systems can depress sea levels, leading to clear sunny days with exceptionally low tides. 
• Conversely, low-pressure systems that contribute to cloudy, rainy conditions typically are associated with tides than are much higher than predicted.

• Harmful algal blooms, or HABs, occur when colonies of algae—simple plants that live in the sea and freshwater—grow out of control while producing toxic or harmful effects on people, fish, shellfish, marine mammals, and birds.
• While many people call these blooms ‘red tides,’ scientists prefer the term harmful algal bloom. 
• During a red tide, algae become so numerous that they discolor coastal waters (hence the name “red tide”). 
• The algal bloom may also deplete oxygen in the waters and/or release toxins that may cause illness in humans and other animals. 
• Major factors influencing red tide events include warm ocean surface temperatures, low salinity, high nutrient content, calm seas, and rain followed by sunny days during the summer months.

• The intertidal zone is an extreme ecosystem because it constantly experiences drastic changes. It is located on marine coastlines, including rocky shores and sandy beaches. The intertidal zone experiences two different states: one at low tide when it is exposed to the air and the other at high tide when it is submerged in seawater. The zone is completely submerged by the tide once or twice every day.
• Organisms that live in the intertidal zone tend to form their own communities across the zone’s elevation gradient. Some species live further up the shore and closer to the high tide line, while others live further down the shore, closer the low tide line. Anything living in the intertidal zone must be able to survive changes in moisture, temperature, and salinity and withstand strong waves.

• When cold and warm ocean current meet, the warm ocean current condenses after getting in contact with cold air and it results into fog.
• It also leads to high rate of precipitation in the region. 
• The circulation in the area where the Labrador Current and Gulf Stream meet is one of the most complex and variable regions in the world.

Pole fleeing force is a geophysical concept invoked in 1915 by Alfred Wegener to explain his ideas of Continental drift.
He suggested that a differential gravitational force (horizontal component of centrifugal force) and the Earth’s flattening would cause continental masses to drift slowly towards the equator.
This force is caused due to the spinning of earth.
The hypothesis was expanded in 1920 but the force is now known to be far too weak to cause plate tectonics. The toughness of the sublayers of the Earth’s crust is much stronger than assumed by Wegener.

• Oceanic crust is the result of erupted mantle material originating from below the plate, cooled and in most instances, modified chemically by seawater.
• Oceanic crust is about 6 km thick, Continental about 10 Km. It is composed of several layers, not including the overlying sediment.
• The topmost layer, about 500 metres (1,650 feet) thick, includes lavas made of basalt (that is, rock material consisting largely of plagioclase [feldspar] and pyroxene).
• Oceanic crust differs from continental crust in several ways: it is thinner, denser, younger, and of different chemical composition.

• Plate tectonics is the modern version of continental drift, a theory first proposed by scientist Alfred Wegener in 1912.
• Wegener didn’t have an explanation for how continents could move around the planet, but researchers do now.
• Plate tectonics is thus said to be the unifying theory of geology.
• The driving force behind plate tectonics is convection in the mantle. Hot material near the Earth’s core rises, and colder mantle rock sinks.

The mapping of the ocean floor and paleomagnetic studies of rocks from oceanic regions revealed the following facts:
(i) It was realised that all along the mid oceanic ridges, volcanic eruptions are common and they bring huge amounts of lava to the surface in this area.
(ii) The rocks equidistant on either sides of the crest of mid-oceanic ridges show remarkable similarities in terms of period of formation, chemical compositions and magnetic properties. Rocks closer to the mid-oceanic ridges are normal polarity and are the youngest. The age of the rocks increases as one moves away from the crest.
(iii) The ocean crust rocks are much younger than the continental rocks. The age of rocks in the oceanic crust is nowhere more than 200 million years old. Some of the continental rock formations are as old as 3,200 million old.
(iv) The sediments on the ocean floor are unexpectedly very thin.
(v) The deep trenches have deep-seated earthquake occurrences while in the mid-oceanic ridge areas, the quake foci have shallow depths. It means lava is in close vicinity.

The energy emanating from within the earth is the main force behind endogenic geomorphic processes. This energy is mostly generated by radioactivity, rotational and tidal friction and primordial heat from the origin of the earth.