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VOLCANO AND TSUNAMI A volcano is a vent in the earth‘s crust from which molten rock material (magma), explosive bursts of gases and volcanic ashes erupt. Destructive Effects of Volcanoes Volcanism can be a greatly damaging natural disaster. The damage is caused by advancing lava which engulfs whole cities. Showers of cinders and bombs can cause damage to life. Violent earthquakes associated with the volcanic activity and mudflows of volcanic ash saturated by heavy rain can bury nearby places. In coastal areas, seismic sea waves (called tsunamis in Japan) are an additional danger which is generated by submarine earth faults where volcanism is active. The volcanic gases that pose the greatest potential hazard to people, animals, agriculture, and property are sulfur dioxide, carbon dioxide, and hydrogen fluoride. Locally, sulfur dioxide gas can lead to acid rain and air pollution downwind from a volcano. Globally, large explosive eruptions that inject a tremendous volume of sulfur aerosols into the stratosphere can lead to lower surface temperatures and promote depletion of the Earth‟s ozone layer. 52
Positive Effects of Volcanoes Volcanism creates new landforms like islands, plateaus, volcanic mountains etc. The volcanic ash and dust are very fertile for farms and orchards. Volcanic rocks yield very fertile soil upon weathering and decomposition. Although steep volcano slopes prevent extensive agriculture, forestry operations on them provide valuable timber resources. Mineral resources, particularly metallic ores are brought to the surface by volcanoes. Sometimes copper and other ores fill the gas-bubble cavities. The famed Kimberlite rock of South Africa, source of diamonds, is the pipe of an ancient volcano. In the vicinity of active volcanoes, waters in the depth are heated from contact with hot magma giving rise to springs and geysers. The heat from the earth‘s interior in areas of volcanic activity is used to generate geothermal electricity. Countries producing geothermal power include USA, Russia, Japan, Italy, New Zealand and Mexico. The Puga valley in Ladakh region and Manikaran (Himachal Pradesh) are promising spots in India for the generation of geothermal electricity. 53
GEYSERS HOT SPRINGS Steam or water at high pressure, along its path, Steam or water at high pressure smoothly flows gets accumulated in small reservoirs, fissures and to the top through the vent and condense at the fractures. Once the pressure exceeds the surface giving rise to a spring. threshold limit, the steam bursts out to the surface disrupting the water at the mouth. Hence the name geyser. Silicate deposits at mouth gives them their Some springs are very colorful because of the distinct colours presence of cyanobacteria of different colors. Found in very few regions. Iceland is famous for Found all across the world its geysers. As scenic features of great beauty, attracting a heavy tourist trade, few landforms outrank volcanoes. At several places, national parks have been set up, centered around volcanoes. As a source of crushed rock for concrete aggregate or railroad ballast, and other engineering purposes, lava rock is often extensively used. TSUNAMI Tsunami is a Japanese word for ―Harbour wave‖. They are also known as seismic sea waves. They are very long-wavelength water waves in oceans or seas. They are commonly referred to as tidal waves because of long wavelengths, although the attractions of the Moon and Sun play no role in their formation. They sometimes come ashore to great heights – tens of metres above mean tide level – and may be extremely destructive. CAUSES A tsunami can be caused by any disturbance that displaces a large water mass from its equilibrium position. The usual immediate cause of a tsunami is sudden displacement in a seabed due to submarine earthquakes sufficient to cause the sudden raising or lowering of a large body of 54
water. The tsunami on December 26, 2004 was caused after an earthquake displaced the seabed off the coast of Sumatra, Indonesia. Large volcanic eruptions along shorelines, such as Krakatoa (1883 CE), have also produced notable tsunamis. A marine volcanic eruption can generate an impulsive force that displaces the water column and gives birth to a tsunami. During a submarine landslide, the equilibrium sea-level is altered by sediment moving along the floor of the sea. Gravitational forces then propagate a tsunami. Landslides along the coast, high intensity explosions can also cause tsunami. Most destructive tsunamis can be caused due to the fall of extra-terrestrial objects on to the earth. 55
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LANDFORMS Davis's geomorphic cycle model says that a landscape undergoes a preliminary uplift that is paired with erosion (the removal or wearing down) of materials in that uplifted landscape. Within the same landscape, precipitation causes streams to flow more rapidly. As they grow their power then cuts into the ground's surface both at the start of the stream and lower down the stream. This creates the stream channels present in many landscapes. RIVERS The landforms created as a result of degradational action (erosion) or aggradational works (deposition) of running water are called fluvial landforms. The fluvial processes may be divided into three physical phases – erosion, transportation and deposition. The depositional action of a stream is influenced by stream velocity and the volume of river load. The decrease in stream velocity reduces the transporting power of the streams which are forced to leave some load to settle down. Increase in river load is effected through accelerated rate of erosion in the source catchment areas consequent upon deforestation. Various landforms resulting from fluvial action are as follows: 57
Other landforms include waterfalls, different types of delta, flowing pattern, etc. They vary depending on the stage of the river lifecycle (young, mature or old), amount of sediments and the resistance by the existing rocks. 58
GLACIAL LANDFORMS A glacier is a moving mass of ice at speeds averaging few meters a day. The largest of Indian glaciers occur in the Karakoram range, viz. Siachen (72 km), while Gangotri in Uttar Pradesh (Himalayas) is 25.5 km long. A glacier is charged with rock debris which is used for erosional activity by moving ice. A glacier during its lifetime creates various landforms which may be classified into erosional and depositional landforms. FIGURE: EROSIONAL LANDFORMS 59
FIGURE: DEPOSITIONAL LANDFORMS Glaciers are important sources of water for rivers. They can assist in sustaining life by regularly replenishing the perennial rivers, but at the same time cause disasters like avalanches. With climate change and global warming, melting glaciers are posing a great challenge to the world countries in the form of rising sea level, emergence of invasive species at mountain tops, change bio- geography of higher latitudes, etc. We must control the warming of the world to better manage ice covered areas. 60
ARID LANDFORMS Arid regions are regions with scanty rainfall. Deserts and Semi-arid regions fall under this category. Wind and water are the major agents of landform development in the deserts. Here, we have both, erosional and depositional features. FIGURE: EROSIONAL AND DEPOSITIONAL ARID LANDFORMS 61
FIGURE: CRESCENT AND BARCHAN SAND DUNES, AND SEIF DUNES (longitudinal sand dunes) Though deserts are areas with minimum water availability and low population density, areas near water sources like oasis are highly populated. Best use of available resources and area-specific agriculture can lead to the development of desert areas at par with fertile areas. 62
KARST TOPOGRAPHY Karst is a landscape which is underlain by limestone which has been eroded by dissolution, producing towers, fissures, sinkholes, etc. It is so named after a province of Yugoslavia on the Adriatic Sea coast where such formations are most noticeable. Karst topography is a landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes, caves etc. Conditions Essential for Full Development of Karst Topography Presence of soluble rocks, preferably limestone at the surface or sub-surface level. These rocks should be dense, highly jointed and thinly bedded. FIGURE: KARST TOPOGRAPHY Limestone is one of the strongest rocks, but only till there are cracks. Cracks make it the most vulnerable to erosion by water, due to formation of calcium carbonate. 63
OCEANOGRAPHY OCEAN CURRENTS Ocean currents are the most important ocean movements because of their influence on climatology of various regions. Ocean currents are like river flow in oceans. They represent a regular volume of water in a definite path and direction. Ocean currents are influenced by two types of forces namely: 1. Primary forces that initiate the movement of water - heating by solar energy, wind, gravity and Coriolis force. 2. Secondary forces that influence the currents to flow - Temperature difference and Salinity difference. GENERAL CHARACTERISTICS OF OCEAN CURRENTS 1. The general movement of the currents in the northern hemisphere is clockwise and in the southern hemisphere, anti-clockwise. This is due to the Coriolis force which is a deflective force and follows Ferrel‟s law. A notable exception to this trend is seen in the northern part of the Indian Ocean where the current movement changes its direction in response to the seasonal change in the direction of monsoon winds. 2. The warm currents move towards the cold seas and cool currents towards the warm seas. In the lower latitudes, the warm currents flow on the eastern shores and cold on the western shores [food for imagination]. The situation is reversed in the higher latitudes. The warm currents move along the western shores and the cold currents along the eastern shores. 3. The shape and position of coasts play an important role in guiding the direction of currents. 64
4. The currents flow not only at the surface but also below the sea surface, due to salinity and temperature difference. For instance, heavy surface water of the Mediterranean Sea sinks and flows westward past Gibraltar as a sub-surface current. EFFECTS OF OCEAN CURRENTS Ocean currents have a number of direct and indirect influences on human activities: Desert formation Cold ocean currents have a direct effect on desert formation in west coast regions of the tropical and subtropical continents. There is fog and most of the areas are arid due to desiccating effect (loss of moisture). Rains Warm ocean currents bring rain to coastal areas and even interiors. Example: Summer Rainfall in British Type climate. 65
Warm currents flow parallel to the east coasts of the continents in tropical and subtropical latitudes. This results in warm and rainy climates. These areas lie in the western margins of the subtropical anti-cyclones. Moderating effect They are responsible for moderate temperatures at coasts. [North Atlantic Drift brings warmness to England. Canary cold current brings cooling effect to Spain, Portugal etc.] Fishing Mixing of cold and warm ocean currents bear richest fishing grounds in the world. Example: Grand Banks around Newfoundland, Canada and North-Eastern Coast of Japan. The mixing of warm and cold currents help to replenish the oxygen and favor the growth of planktons, the primary food for fish population. The best fishing grounds of the world exist mainly in these mixing zones. Drizzle Mixing of cold and warm ocean currents create foggy weather where precipitation occurs in the form of drizzle [Newfoundland]. Climate Ocean currents result in: Warm and rainy climates in tropical and subtropical latitudes [Florida, Natal etc.], Cold and dry climates on the western margins in the sub-tropics due to desiccating effect, Foggy weather and drizzle in the mixing zones, Moderate clime along the western costs in the sub-tropics. Tropical cyclones They pile up warm waters in tropics and this warm water is the major force behind tropical cyclones. Navigation Currents are referred to by their ―drift‖. Usually, the currents are strongest near the surface and may attain speeds over five knots. Ships usually follow routes which are aided by ocean currents and winds. 66
Example: If a ship wants to travel from Mexico to Philippines, it can use the route along the North Equatorial Drift which flows from east to west. When it wants to travel from Philippines to Mexico, it can follow the route along the doldrums when there is counter equatorial current [we will study this in next post] flowing from west to east . 67
TEMPERATURE PROFILE OF THE OCEANS The study of the temperature of the oceans is important for determining the 1. movement of large volumes of water (vertical and horizontal ocean currents), 2. type and distribution of marine organisms at various depths of oceans, 3. climate of coastal lands, etc. Source of Heat in Oceans The sun is the principal source of energy (Insolation). The ocean is also heated by the inner heat of the ocean itself (earth‘s interior is hot. At the sea surface, the crust is only about 5 to 30 km thick). But this heat is negligible compared to that received from sun. How do deep water marine organisms survive in spite of absence of sunlight? Photic zone is only about few hundred meters. It depends on lot of factors like turbidity, presence of algae etc. There are no enough primary producers below few hundred meters till the ocean bottom. At the sea bottom, there are bacteria that make use of heat supplied by earth‟s interior to prepare food. So, they are the primary producers. Other organisms feed on these primary producers and subsequent secondary producers. So, the heat from earth supports wide ranging deep water marine organisms. But the productivity is too low compared to ocean surface. The ocean water is heated by three processes. 1. Absorption of sun‟s radiation. 68
2. The conventional currents: Since the temperature of the earth increases with increasing depth, the ocean water at great depths is heated faster than the upper water layers. So, convectional oceanic circulations develop causing circulation of heat in water. 3. Heat is produced due to friction caused by the surface wind and the tidal currents which increase stress on the water body. The ocean water is cooled by 1. Back radiation (heat budget) from the sea surface takes place as the solar energy once received is reradiated as long wave radiation (terrestrial radiation or infrared radiation) from the seawater. 2. Exchange of heat between the sea and the atmosphere if there is temperature difference. 3. Evaporation: Heat is lost in the form of latent heat of evaporation (atmosphere gains this heat in the form of latent heat of condensation). FACTORS AFFECTING TEMPERATURE DISTRIBUTION IN OCEANS Insolation: The average daily duration of insolation and its intensity. Heat loss: The loss of energy by reflection, scattering, evaporation and radiation. Albedo: The albedo of the sea (depending on the angle of sun rays). The physical characteristics of the sea surface: Boiling point of the sea water is increased in the case of higher salinity and vice versa. The presence of submarine ridges and sills [Marginal Seas]: Temperature is affected due to lesser mixing of waters on the opposite sides of the ridges or sills. The shape of the ocean: The latitudinally extensive seas in low latitude regions have warmer surface water than longitudinally extensive sea [Mediterranean Sea records higher temperature than the longitudinally extensive Gulf of California]. The enclosed seas (Marginal Seas – Gulf, Bay etc.) in the low latitudes record relatively higher temperature than the open seas; whereas the enclosed seas in the high latitudes have lower temperature than the open seas. Local weather conditions such as cyclones. 69
Unequal distribution of land and water: The oceans in the northern hemisphere receive more heat due to their contact with larger extent of land than the oceans in the southern hemisphere. Prevalent winds generate horizontal and sometimes vertical ocean currents: The winds blowing from the land towards the oceans (off-shore winds-moving away from the shore) drive warm surface water away from the coast resulting in the upwelling of cold water from below (This happens near Peruvian Coast in normal years. El-Nino). Contrary to this, the onshore winds (winds flowing from oceans into continents) pile up warm water near the coast and this raises the temperature (This happens near the Peruvian coast during El Nino event)(In normal years, North-eastern Australia and Western Indonesian islands see this kind of warm ocean waters due to Walker Cell or Walker Circulation). Ocean currents: Warm ocean currents raise the temperature in cold areas while the cold currents decrease the temperature in warm ocean areas. Gulf Stream (warm current) raises the temperature near the eastern coast of North America and the West Coast of Europe while the Labrador Current (cold current) lowers the temperature near the north-east coast of North America (Near Newfoundland). All these factors influence the temperature of the ocean currents locally. 70
FIGURE: VERTICAL TEMPERATURE DISTRIBUTION OF OCEANS FIGURE: OCEAN BOTTOM TOPOGRAPHY AND ZONES (based on penetration of light) 71
OCEAN SALINITY Salinity is the term used to define the total content of dissolved salts in sea water. It is calculated as the amount of salt (in gm) dissolved in 1,000 gm (1 kg) of seawater. It is usually expressed as parts per thousand or ppt.Salinity of 24.7 (24.7 o/oo) has been considered as the upper limit to demarcate ‗brackish water‟. Salinity determines compressibility, thermal expansion, temperature and density, absorption of insolation, evaporation and humidity. It also influences the composition and movement of the sea water and the distribution of fish and other marine resources. FACTORS AFFECTING OCEAN SALINITY The salinity of water in the surface layer of oceans depend mainly on evaporation and precipitation. Surface salinity is greatly influenced in coastal regions by the fresh water flow from rivers, and in polar regions by the processes of freezing and thawing of ice. Wind, also influences salinity of an area by transferring water to other areas. The ocean currents contribute to the salinity variations. Salinity, temperature and density of water are interrelated. Hence, any change in the temperature or density influences the salinity of an area. 72
FIGURE: VERTICAL DISTRIBUTION OF SALINITY FIGURE: GLOBAL SURFACE SALINITY FACTORS AFFECTING GLOBAL SALINITY PROFILE OF OCEANS High salinity regions In the land locked Red Sea, it is as high as 41. In hot and dry regions, where evaporation is high, the salinity sometimes reaches to 70. Comparatively Low salinity regions In the estuaries (enclosed mouth of a river where fresh and saline water get mixed) and the Arctic, the salinity fluctuates from 0 – 35, seasonally (fresh water coming from ice caps). Pacific The salinity variation in the Pacific Ocean is mainly due to its shape and larger areal extent. 73
Atlantic The average salinity of the Atlantic Ocean is around 36-37. The equatorial region of the Atlantic Ocean has a salinity of about 35. Near the equator, there is heavy rainfall, high relative humidity, cloudiness and calm air of the doldrums. The polar areas experience very little evaporation and receive large amounts of fresh water from the melting of ice. This leads to low levels of salinity, ranging between 20 and 32. Maximum salinity (37) is observed between 20° N and 30° N and 20° W – 60° W. It gradually decreases towards the north. Indian Ocean The average salinity of the Indian Ocean is 35. The low salinity trend is observed in the Bay of Bengal due to influx of river water by the river Ganga. On the contrary, the Arabian Sea shows higher salinity due to high evaporation and low influx of fresh water. Marginal seas The North Sea, in spite of its location in higher latitudes, records higher salinity due to more saline water brought by the North Atlantic Drift. Baltic Sea records low salinity due to influx of river waters in large quantity. The Mediterranean Sea records higher salinity due to high evaporation. Salinity is, however, very low in Black Sea due to enormous fresh water influx by rivers. Inland seas and lakes The salinity of the inland Seas and lakes is very high because of the regular supply of salt by the rivers falling into them. Their water becomes progressively more saline due to evaporation. For instance, the salinity of the Great Salt Lake , (Utah, USA), the Dead Sea and the Lake Van in Turkey is 220, 240 and 330 respectively. 74
The oceans and salt lakes are becoming more salty as time goes on because the rivers dump more salt into them, while fresh water is lost due to evaporation. Cold and warm water mixing zones Salinity decreases from 35 – 31 on the western parts of the northern hemisphere because of the influx of melted water from the Arctic region. Sub-Surface Salinity With depth, the salinity also varies, but this variation again is subject to latitudinal difference. The decrease is also influenced by cold and warm currents. In high latitudes, salinity increases with depth. In the middle latitudes, it increases up to 35 metres and then it decreases. At the equator, surface salinity is lower. 75
CORAL REEFS AND CORAL BLEACHING Coral reefs are built by and made up of thousands of tiny animals—coral polyps—that are related to anemones and jellyfish. Polyps are shallow water organisms which have a soft body covered by a calcareous skeleton. The polyps extract calcium salts from sea water to form these hard skeletons. They live in colonies fastened to the rocky sea floor. The tubular skeletons grow upwards and outwards as a cemented calcareous rocky mass, collectively called corals. When the coral polyps die, they shed their skeleton [coral] on which new polyps grow. The cycle is repeated for over millions of years leading to accumulation of layers of corals [shallow rock created by these depositions is called reef]. These layers at different stages give rise to various marine landforms. One such important landform is called coral reef. Coral reefs over a period of time transform or evolve into coral islands (Lakshadweep). IDEAL CONDITIONS FOR GROWTH OF CORALS Corals are highly susceptible to quick changes. They grow in regions where climate is significantly stable for a long period of time. Conditions can be enumerated as: Perpetually warm waters: Corals thrive in tropical waters [30°N and 30°S latitudes, the temperature of water is around 20°C] where diurnal and annual temperature ranges are very narrow. Shallow water: Coral require fairly good amount of sunlight to survive. The ideal depths for coral growth are 45 m to 55 m below sea surface, where there is abundant sunlight available. Clear salt water: Clear salt water is suitable for coral growth, while both fresh water and highly saline water are harmful. Abundant Plankton: Adequate supply of oxygen and microscopic marine food, called plankton [phytoplankton], is essential for growth. As the plankton is more abundant on the seaward side, corals grow rapidly on the seaward side. Little or no pollution: Corals are highly fragile and are vulnerable to climate change and pollution and even a minute increase in marine pollution can be catastrophic. 76
CONCLUSION Coral bleaching is a direct outcome of climate change, global warming and ocean acidification, most of which are results of human exploitation. It is important to conserve the most biologically diverse systems on planet Earth. Countries like Australia also receive good number of tourists and economic gains. Thus, efforts like coral transplantation, curbing marine pollution, controlling climate change, etc, have become need of the hour. Though corals have high resilience, they have the minimum resistance and get destroyed even on minimum changes in the ideal conditions meant for its growth. 77
INDIAN GEOGRAPHY 78
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COASTLINE OF INDIA India has a coastline of 7516.6 Km [6100 km of mainland coastline + coastline of 1197 Indian islands] touching 13 States and Union Territories (UTs). The straight and regular coastline of India is the result of faulting of the Gondwanaland during the Cretaceous period. {Continental Drift} As such the coast of India does not offer many sites for good natural harbours. The Bay of Bengal and the Arabian Sea came into being during the Cretaceous or early Tertiary period after the disintegration of Gondwanaland. 80
SIGNIFICANCE OF THE COASTAL PLAINS Large parts of the coastal plains of India are covered by fertile soils on which different crops are grown. Rice is the main crop of these areas. Coconut trees grow all along the coast. The entire length of the coast is dotted with big and small ports which help in carrying out trade. The sedimentary rocks of these plains are said to contain large deposits of mineral oil (KG Basin). The sands of Kerala coast have large quantity of MONAZITE which is used for nuclear power. Fishing is an important occupation of the people living in the coastal areas. Low lying areas of Gujarat are famous for producing salt. Kerala backwaters are important tourist destinations. Goa provides good beaches. This is also an important tourist destination. CONCLUSION Coastal areas are important parts of India‘s development journey, along with the islands. Realising its importance and geostrategic relevance, government has started focussed interventions for their all- round sustainable development. New Coastal Regulation Zone rules are a setback to the precedent and must be corrected at the earliest. Kasturirangan and Madhav Gadgill recommendations must be implemented at the earliest to establish Eco-Sensitive Zones for Western Ghats conservation. The region has very high potential for economy, tourism, mineral exploration, trade as well as biodiversity conservation. 81
NATURAL VEGETATION 82
THIS IS THE BROAD SPATIAL DISTRIBUTION OF NATURAL VEGETATION IN INDIA. FOR DETAILED DISCUSSION ABOUT FACTORS, THREATS AND SOLUTIONS, PLEASE VISIT OUR YOUTUBE CHANNEL FOR GUESS PAPER VIDEOS BY ANKIT SIR. SCAN THE CODE OR CLICK THE LINK BELOW: https://www.youtube.com/watch?v=DLt3Lh5BwrU 83
SOIL OF INDIA Soil is the thin top layer on the earth‘s crust comprising rock particles mixed with organic matter. Pedology is the study of soils in their natural environment. Pedogenesis is the natural process of soil formation that includes a variety of processes such as weathering, leaching, calcification etc. The soil formation is mainly related to the parent rock material, surface relief, climate and natural vegetation. The soil is formed by the breaking down of rocks by the action of wind, water and climate. A vertical section through different layers of the soil is called the soil profile: 84
Geologically, Indian soils can broadly be divided into soils of peninsular India and soils of extra- peninsular India. The soils of Peninsular India are formed by the decomposition of rocks in situ, i.e. directly from the underlying rocks. They are transported and re-deposited to a limited extent and are known as sedentary soils. The soils of the Extra-Peninsula are formed due to the depositional work of rivers and wind. They are very deep and are often referred to as transported or azonal soils. 85
FACTORS AFFECTING SOIL CHARACTERISTICS OF INDIAN SOILS Most soils are old and mature. Soils of the peninsular plateau are much older than the soils of the great northern plain. Indian soils are largely deficient in nitrogen, mineral salts, humus and other organic materials. Plains and valleys have thick layers of soils while hilly and plateau areas depict thin soil cover. Some soils like alluvial and black soils are fertile while some other soils such as laterite, desert and alkaline soils lack in fertility and do not yield good harvest. Indian soils have been used for cultivation for hundreds of years and have lost much of their fertility. 86
CONCLUSION Indian soils have suffered severe overexploitation over the years, especially in Green revolution areas. To meet the nutrition needs of the world‘s second largest population, agriculture in India has greatly misused and reused without replenishment, soils of the country. Problems can be enumerated as: Soil erosion (Himalayan region, Chambal Ravines etc.) Deficiency in fertility (Red, lateritic and other soils) Desertification (around Thar desert, rain-shadow regions like parts of Karnataka, Telangana etc.) Waterlogging (Punjab-Haryana plain) Salinity and alkalinity (excessively irrigated regions of Punjab, Haryana, and Karnataka etc.) Wasteland development Over exploitation of soils due to increase in population and rise in living standards and encroachment of agricultural land due to urban and transport development. Therefore, we must move towards proper land use planning, organic agriculture and Soil Health Card for nutrient mix according to the soil composition. 87
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