Indian Geography Lecture 1 - Ocean Salinity PDF

# **Indian Geography** ## **Lecture 1: Indian Geography - Introduction** ### **Ocean Salinity** * Salinity means the total content of dissolved salts in the Sea or Ocean. * Salinity is calculated as the amount of salt dissolved in 1000 gm of seawater. * It is generally expressed as 'parts per tho...

# **Indian Geography** ## **Lecture 1: Indian Geography - Introduction** ### **Ocean Salinity** * Salinity means the total content of dissolved salts in the Sea or Ocean. * Salinity is calculated as the amount of salt dissolved in 1000 gm of seawater. * It is generally expressed as 'parts per thousand' (ppt). * A salinity of 24.7% has been regarded as the upper limit to fix 'brackish water'. * It is a significant factor in deciding several characteristics of the chemistry. * Salinity determines the possibility, of thermal expansion, temperature, density, absorption of insolation, evaporation & humidity. * It also influences the composition and movement of the sea water and the distribution of fish and other marine resources. ### **Share of Different Salts** * Sodium chloride - 77.7% * Magnesium chloride - 10.9% * Magnesium sulphate - 4.7% * Calcium sulphate - 3.6% * Potassium sulphate - 2.5% ### **Factors Affecting Salinity of the Ocean Water** * There are sections of the ocean where there is little rain yet there is a lot of evaporation due to the warm, dry breezes. * This evaporation removes water, but because water vapor leaves salt behind when it rises into the atmosphere, the saltiness of the saltwater grows. * The ocean becomes denser as a result of this. * High salinity can be found in the North and South Atlantic, which are locations with strong winds and little rain. * **Rate of Evaporation:** * The ocean between 20°N and 30°N latitudes has more salinity than the temperate latitude ocean due to a higher rate of evaporation (because of high temperature). * However, due to the considerations indicated in the next paragraph, this does not entail that tropical oceans will have more salinity. ### **Amount of Freshwater Added** * The places having high daily rainfall, high relative humidity, and addition by freshwater have low salinity. * E.g. Oceans into which huge rivers like Amazon, Congo, Ganges, Irrawaddy, and Mekong drain have lower salinity. * The Baltic, Arctic, and Antarctic waters have a salinity of <32 ppt because much freshwater is added from the melting of icebergs, as well as by several large poleward-bound rivers. ### **The Degree of Water Mixing by Currents** * As there is no mixing of freshwater and continual evaporation in land-locked (enclosed by lands) areas, the salinity is higher. * For example, the Black Sea, the Caspian Sea, the Red Sea, and the Persian Gulf. * Where there is free mixing of water by surface and subsurface currents, the salinity range is small. ### **Horizontal Distribution of Salinity** * **High Salinity Regions** * In the landlocked Red Sea, (don't confuse this with the Dead Sea which has much greater salinity), it is as high as 41. * In hot and dry regions, where evaporation is high, the salinity sometimes reaches 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 (freshwater coming from ice caps). * **Pacific:** * The salinity variation in the Pacific Ocean is mainly due to its shape and larger areal extent. ### **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 freshwater 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 the influx of river water from the river Ganga. * On the contrary, the Arabian Sea shows higher salinity due to high evaporation and a 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. * The Baltic Sea records low salinity due to the influx of river waters in large quantities. * The Mediterranean Sea records higher salinity due to high evaporation. * Salinity is, however, very low in the Black Sea due to the enormous freshwater influx by rivers. ### **Vertical Distribution of Salinity** * Salinity changes with depth, but the way it changes depends upon the location of the sea. * Salinity at the surface increases by the loss of water to ice or evaporation or decreases by the input of freshwaters, such as from the rivers. * Salinity at depth is very much fixed because there is no way that water is 'lost', or the salt is 'added'. There is a marked difference in the salinity between the surface zones and the deep zones of the oceans. * The lower salinity water rests above the higher salinity dense water. * Salinity, generally, increases with depth and there is a distinct zone called the halocline (compare this with thermocline), where salinity increases sharply. * Other factors being constant, increasing the salinity of seawater causes its density to increase. High-salinity seawater, generally, sinks below the lower-salinity water which leads to stratification by salinity. ## **Note:** * **Source of Indian Geography:** * Indian Geography - Class 11th NCERT * Class Notes * Addition from Current Affairs * Human Geography - Class 12th NCERT ## **Introduction to India** * India is a very vast country. India is located entirely in the northern hemisphere, specifically in the south-central part of the continent of Asia, the mainland extends between 8°4'N and 37°6'N, and longitudes 68°7'E and 97°25'E area of the world. * India has a land boundary of about 15,200 km and the total length of the coastline of the mainland, including Andaman and Nicobar and Lakshadweep, is 7,516.6 km. * India is bounded by the Young Fold Mountains in the northwest, north, and northeast. South of about 22° north latitude, it begins to taper and extends towards the Indian Ocean, dividing it into two seas, the Arabian Sea on the west and the Bay of Bengal on the east. The latitudinal and longitudinal extent of the mainland is about 30°. Despite this fact, the east-west extent appears to be smaller than the north-south extent. * From Gujarat to Arunachal Pradesh, there is a time lag of two hours. Hence, time along the Standard Meridian of India (82°30′E) passing through Mirzapur (in Uttar Pradesh) is taken as the standard time for the whole country. * The latitudinal extent influences the duration of day and night, as one moves from south to north. * The Tropic of Cancer passes through eight states in India: Gujarat (Jasdan), Rajasthan (Kalinjarh), Madhya Pradesh (Shajapur), Chhattisgarh (Sonhat), Jharkhand (Lohardaga), West Bengal (Krishnanagar), Tripura (Udaipur), and Mizoram (Champhai). * The southernmost point of the country is the Pygmalion Point or Indira Point is located at 6° 45′ N latitude. * The north-south extent from Indira Col in Kashmir to Kanniyakumari is 3,214 km. * East-west width from the Rann of Kachachh to Arunachal Pradesh is 2,933 km. * With an area of 32,87,263 sq km, India is the seventh-largest country in the world. * India accounts for about 2.4 percent of the total surface area of the world. * The Tropic of Cancer passes through the middle of the country dividing it into two latitudinal halves. * The area to the north of the Tropic of Cancer is nearly twice the area that lies to the south of it. ## **2 Time Zones in India** * Time zones in India were first set up in 1884, during the British Raj. Before independence, India followed three major time zones Bombay, Calcutta, and Madras Time. * Indian Standard Time is an anachronism like many systems that were inherited from the British. It was in 1906 that India had a single IST running through the center of the country. ## **What is the Need for Two-Time Zones?** * **Large Geographical Extent:** India is geographically the second-largest country (after China) to not have multiple time zones. * India stretches from 97°25'E in Arunachal to 68°7'E in Gujarat - almost 30 degrees of longitude which is more than enough to have two time zones. * **Early Sunrise and Sunset:** The demand for two time zones rose because northeastern India (NER) and the Andaman and Nicobar Islands (ANI), due to their geography, witness an early sunrise and sunset relative to the rest of the country. * The NER has long complained about the effect of a single time zone on their lives and their economies, they lose important daylight which can be used productively as the sun rises as early as 4 am in summer while the government offices open at 10 am. * **Sync with Circadian Rhythm:** Many people in India operate in a time zone that is not an appropriate diurnal cycle for them, people's productivity and efficiency follow a biological clock that is synchronized with the daily light-dark cycles. ### **Advantages** * **Efficiency:** This would lead to greater efficiencies among the workforce and in energy consumption. * There are economic benefits to having two different time zones, people will be able to work better and plan better, according to their natural cycles. * In fact, tea gardens in Assam have long set their clocks one hour ahead of the IST, creating their own informal time zone (Chaibagaan Time). * **Environment Protection:** Advancing IST by just a half hour would result in saving 2.7 billion units of electricity every year by using the wasted daylight hours. * Conserving electricity is critical for the Indian economy, which is suffering from a crippling power deficit. * According to CSIR-NPL, India might save ₹1,000 crore per year if it can conserve electricity by implementing two time zones. * **Societal Benefits:** Many social policy objectives can be achieved by having two time zones such as reducing road accidents and improving women's safety. * Moreover, according to research, people in countries with more than one time zone were able to concentrate better on their strengths and shortcomings, resulting in the best outcomes. * Changing the time zone allowed employees to develop healthier eating, sleeping, and working habits, which had positive outcomes. ### **Disadvantages:** * **Timing Mismatch:** Mismatches in office timings, different working hours for banks, and a chance that railway accidents might become more frequent. * Implementing two time zones will require synchronizing railway traffic which otherwise will create utter confusion. * It would lead to confusion in travel schedules as people travel mostly by road and not by air as in the West where all they need to do is set their clocks right. * **Chaos at the Border of Time Zones:** With significant illiteracy levels and low awareness, if the country were divided into two time zones, there would be chaos at the border between the two zones. It would mean resetting clocks with each crossing of the time zone. * Marking the dividing line of the two zones would also be a problem. * **Prone to Increase Divide:** Two time zones can have adverse political consequences as India apart from getting divided on the lines of religion, caste, race, language, etc., now will get divided on the lines of Time Zones. * Bringing in two time zones will create a divide between the NER and the rest of the country, a separate time zone would make them see themselves as separate from the rest of the country and may provoke secessionist demands. * **Infrastructural Burden:** CSIR-NPL would need a second laboratory in the new time zone. This would consist of 'Primary Time Ensemble- II', traceable to the UTC at the International Bureau of Weights and Measures (BIPM), France. ## **Way Forward:** * Factors like the impact of sunrise and sunset timings on the biological activities of people, and synchronizing sunrise and sunset timings with office hours should be carefully studied. * Minimization of spatial extension at the proposed border of time demarcation etc. needs to be taken care of. * It is important to consult all stakeholders and arrive at a better solution so as to use the lost light hours that are dimmed by a common IST. ## **Coastline of India:** * India is a country that is surrounded by the sea on three of its sides. The coastal plains in India are along the west and east of the country. * Extending up to 7516.6 km, the coastal plains in India are of two types: Eastern coastal plains and Western coastal plains. ## **India, Tropical or Temperate Country?** ### **Physical Geographical Reasons:** * The country is separated from the rest of Asia by the Himalayas. * Its climate is dominated by tropical monsoons and the temperate air masses are blocked by the Himalayas. * The climatic perspective indicates that the entire region below the Himalayas is fundamentally tropical. * Although the night temperatures in Winter at several places in North India may come down to the level of those prevailing in temperate lands, yet clear skies and intense insolation raise the day temperatures to a tropical level. ### **Cultural Geographical Reasons:** * Settlements, diseases, agricultural, and primary economic activities are all tropical.