OneTime: Test: Class 11 Geography NCERT Based - 2 - UPSC MCQ

• Natural vegetation means the plants that have not been grown by humans. It doesn’t need help from humans and gets whatever it needs from its natural environment. There is a close relationship between height of land and the character of vegetations.

• With the change in height, the climate changes and that changes natural vegetation. The growth of vegetation depends on temperature and moisture. It also depends on factors like slope and thickness of soil.

• It is categorized into three broad categories: Forest, grassland and shrubs. Natural vegetation means the plants that have not been grown by humans. It doesn’t need help from humans and gets whatever it needs from its natural environment. There is a close relationship between height of land and the character of vegetations. With the change in height, the climate changes and that changes natural vegetation.

• Desertification, also called desertization, the process by which natural or human causes reduce the biological productivity of drylands (arid and semiarid lands). Declines in productivity may be the result of climate change, deforestation, overgrazing, poverty, political instability, unsustainable irrigation practices, or combinations of these factors.

• The concept does not refer to the physical expansion of existing deserts but rather to the various processes that threaten all dryland ecosystems, including deserts as well as grasslands and scrublands.

• Slightly less than half of Earth’s ice-free land surface—approximately 52 million square km (about 20 million square miles)—is drylands, and these drylands cover some of the world’s poorest countries. 1. Irrigated croplands, whose soils are often degraded by the accumulation of salts.

2. Rain-fed croplands, which experience unreliable rainfall and wind-driven soil erosion.

3. Grazing lands, which are harmed by overgrazing, soil compaction, and erosion.

4. Dry woodlands, which are plagued by the overconsumption of fuelwood. Solutions To Desertification: The struggle against desertification can occur at several levels. Since regional variations in climate are the main causes of the loss of dryland productivity, it is important to understand the influence of global warming in specific dryland regions. According to some models of climate change, many grasslands in western North America, for example, are predicted to be at greater risk of drought due to projected increases in summer temperatures and changes to existing rainfall patterns. Many authorities argue that since desertification and global warming are so closely related, one of the main solutions to the former may be the implementation of effective economic policies (such as carbon trading) and technical measures (such as carbon sequestration) that reduce the production of greenhouse gases. At local scales, however, desertification is often the result of unsustainable land and soil management. To maintain the biological productivity of the land, soil conservation is often the priority. A number of innovative solutions have been devised that range from relatively simple changes in how people grow crops to labour-intensive landscape engineering projects.

Some of the techniques that may help ameliorate the consequences of desertification in irrigated croplands, rain-fed croplands, grazing lands, and dry woodlands include:

1. Salt traps, which involve the creation of so called void layers of gravel and sand at certain depths in the soil. Salt traps prevent salts from reaching the surface of the soil and also help to inhibit water loss.

2. Irrigation improvements, which can inhibit water loss from evaporation and prevent salt accumulation. This technique involves changes in the design of irrigation systems to prevent water from pooling or evaporating easily from the soil.

3. Cover crops, which prevent soil erosion from wind and water. They can also reduce the local effects of drought. On larger scales, plant cover can help maintain normal rainfall patterns. Cover crops may be perennials or fast-growing annuals.

4. Crop rotation, which involves the alternation of different crops on the same plot of land over different growing seasons. This technique can help maintain the productivity of the soil by replenishing critical nutrients removed during harvesting.

5. Rotational grazing, which is the process of limiting the grazing pressure of livestock in a given area. Livestock are frequently moved to new grazing areas before they cause permanent damage to the plants and soil of any one area.

6.Terracing, which involves the creation of multiple levels of flat ground that appear as long steps cut into hillsides. The technique slows the pace of runoff, which reduces soil erosion and retards overall water loss.

7. Contour bunding (or contour bundling), which involves the placement of lines of stones along the natural rises of a landscape, and contour farming.

These techniques help to capture and hold rainfall before it can become runoff. They also inhibit wind erosion by keeping the soil heavy and moist.

8. Windbreaks, which involve the establishment of lines of fast growing trees planted at right angles to the prevailing surface winds. They are primarily used to slow winddriven soil erosion but may be used to inhibit the encroachment of sand dunes.

9. Dune stabilization, which involves the conservation of the plant community living along the sides of dunes. The upper parts of plants help protect the soil from surface winds, whereas the root network below keeps the soil together.

10. Charcoal conversion improvements, which include the use of steel or mud kilns or high-pressure compacting equipment to press the wood and other plant residues into briquettes. Conversion improvements retain a greater fraction of the heating potential of fuelwood.

• Soil retrogression and degradation are two important regressive evolution processes which take place due to loss of equilibrium of a stable soil. Retrogression primarily occurs due to soil erosion.

• Soil Degradation is an evolution process which is different from natural evolution and is largely related to the local climate and vegetation. It is due to the replacement of primary plant communities (known as climax) by the secondary communities. This replacement in turn modifies the humus composition and amount, which will ultimately affect the formation of the soil. To bear in mind is that degradation is largely associated with human activity.

• In simple words, soil degradation is any sort of change or disturbance in the soil which is undesirable. The consequences of both the processes are-

1. Impacts the yield bearing capacity of the soil.

2. A deterioration in water quality.

3. Economic loss- this is a major negative externality.

• Soil Erosion is a common term that is often confused with soil degradation as a whole, but in fact refers only to absolute soil losses in terms of topsoil and nutrients.

• This is indeed the most visible effect of soil degradation, but does not cover all of its aspects. Soil erosion is a natural process in mountainous areas, but is often made much worse by poor management practices. Soil erosion i.e., the displacement of the upper fertile layer of soil, is a natural process that occurs at a very slow pace due to -

1. Moving Water (splash erosion, sheet erosion, rill erosion, and gully erosion)

2. Wind (surface creep, saltation and suspension)

3. Glaciers (due to heavy weight/ huge mass)

4. Gravity (causes mass movement)

• Mass movement, also called Mass Wasting, bulk movements of soil and rock debris down slopes in response to the pull of gravity, or the rapid or gradual sinking of the Earth’s ground surface in a predominantly vertical direction.

• Formerly, the term mass wasting referred to a variety of processes by which large masses of crustal materials are moved by gravity from one place to another. More recently, the term mass movement has been substituted to include mass wasting processes and the sinking of confined areas of the Earth’s ground surface.

• Mass movements on slopes and sinking mass movements are often aided by water and the significance of both types is the part each plays in the alteration of landforms. The variety of downslope mass movements reflects the diversity of factors that are responsible for their origin.

• Such factors include: weathering or erosional debris cover on slopes, which is usually liable to mass movement; the character and structure of rocks, such as resistant permeable beds prone to sliding because of underlying impermeable rocks; the removal of the vegetation cover, which increases the slope’s susceptibility to mass movement by reducing its stability; artificial or natural increases in the slope’s steepness, which will usually induce mass movement; earthquake tremors, which affect the slope equilibrium and increase the likelihood of mass movement; and flowing groundwater, which exerts pressure on soil particles and impairs slope stability.

• The word laterite has been derived from the Latin word ‘Later’ which means brick. These soils when wet are as soft as butter but become hard and cloddy on drying. Therefore, these are widely cut as bricks for use in house construction. Formation: The lateritic soils are particularly found on high flat erosion surfaces in areas of high(>200cm) and seasonal rainfall. The alternating wet and dry seasons lead to the leaching away of the siliceous matter of the rocks leaving behind the compounds of iron and aluminium. These are zonal soils.

• Areas: These soils have mainly developed in the higher areas of the Peninsular plateau. The laterite soils are commonly found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh and the hilly areas of Orissa and Assam. Soil Colour: Reddish brown in colour due to the presence of iron oxide.

• Natural disasters can be categorized as "acute" or "slow" in their onset. They are predictable because they cluster in geographic areas. Natural hazards are unpreventable and, for the most part, uncontrollable.

• Even if quick recovery occurs, natural disasters can have long term effects. Natural disasters with acute onsets include events such as earthquake, flood, hurricane or typhoon, tornado, fire, tsunami or storm surge, avalanche, volcanic eruption, extreme cold or blizzard, and heat wave.

• Natural hazards with a slow or gradual onset include drought, famine, desertification, deforestation, and pest infestation. Natural disasters – such as hurricanes, cyclones, earthquakes, mudslides, floods, wildfires, volcanic eruptions and weather events like extreme droughts and monsoons – are likely increasing in frequency due to climate change.

• Floods are natural occurrences where an area or land that is normally dry abruptly becomes submerged in water.

• In simple terms, flood can be defined as an overflow of large quantities of water onto a normally dry land.

• Flooding happens in many ways due to overflow of streams, rivers, lakes or oceans or as a result of excessive rain.

• Whenever flooding takes place, there is the possibility of loss of life, hardship to people, and extensive damage to property. This is because flooding can carry bridges, cars, houses, and even people.

• With the advancement of technology such as satellite and remote-sensing equipment, flood waves can be tracked as the water level rises. Evacuation is possible with suitable monitoring and warning. A warning is issued by the Central Water Commission (CWC), Irrigation and Flood Control Department and Water Resources Department.

1. Mapping of the Flood Prone Areas: Flood hazard mapping will give the proper indication of water flow during floods. Land use Control It will reduce danger of life and property, when the waters inundate the flood plains and the coastal areas. No major development should be permitted in the areas which are subjected to high flooding.

2. Flood Control: It aims to reduce flood damage. This can be done by decreasing the amount of run-off with the help of reforestation. Flood diversion includes levees, embankments, dams and channel improvement. Dams can store water and can release water at a manageable rate. But the failure of dams in earthquakes and operation of releasing the water can cause floods in the lower areas.

3. Flood Proofing: It reduces the risk of damage. Measures include use of sandbags to keep flood water away, blocking or sealing of doors and windows of houses, etc. Restoration of Original Drainage System Drainage system is generally choked by the construction of roads, canals, railway tracks etc. Floods could be checked if the original form of drainage system is restored.

• Earthquake is one of the major natural disasters. Every year it causes a huge loss of life and property all around the world. Proper strategies and awareness about disaster management is the need of the hour.

• This will protect us from the losses and help to cope up with these hazards. However, in order to reduce the destruction caused by these occurrences the disaster management committee has laid some safety measures.

• An earthquake is the shaking of the surface of Earth due to the sudden release of energy in the Earth’s crust, as a result, seismic waves (also known as S waves)are created.

• The seismic activities in an area determine the type and intensity of the earthquake. Earthquakes are caused due to sudden tectonic movements in the earth’s crust. When the tectonic plates slide over one another, there is a cause of orogeny which results in earthquakes and volcanoes.

• These disturbances cause vibrations which spread in all the directions. As there is a relative motion of these plates, there is stress built up, which breaks by releasing the stored energy known as shock waves.

• Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the depths of the ocean, tsunami waves do not dramatically increase in height. But as the waves travel inland, they build up to higher and higher heights as the depth of the ocean decreases.

• The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. While tsunamis are often referred to as tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves.

• There are wide varieties of the names given to the denudation process whereby soil or rocks are displaced along the slope by mainly gravitational forces and landslides are one them.

• Landslides refer to the movement of mass of rock, debris or earth down the slope, when the shear stress exceeds the shear strength of the material. It occurs when the consequence of a complex field of forces (stress is a force per unit area) active on a mass of rock or soil on the slope. It happens due to geological causes, morphological causes, physical causes and human causes.

There are two parameters that determine the landslides are as follows:

1. Increase of shear stress: It happens due to the removal of lateral and underlying support; increase of lateral forces as well as load; transitory stresses like blasting, earthquakes etc.; and geological movement.

2. Decrease of material strength: It happens due to the weathering, pore water pressure and changes in structure. The incidents of landslides are increasing day by day due to the over urbanisation, massive deforestation, construction and development work in landslide prone areas.