Environmental acts in India Source by Tamil Nadu Samacheer Kalvi book
Wildlife Protection Act 1972
This law provides protection to wild animals and birds. This is an Act of the Parliament. By this law, protection is provided to wild animals, birds, and plants.
This law extends to the whole of India. Its features are the establishment of Wildlife Sanctuaries, National Parts, etc. The next feature is to prohibit the hunting of endangered species.
It also provides the license for the sale, transfer, and possession of wildlife species.
The significance of the Wildlife Protection Act 1972 is, it regulates the sanctuaries, national parks, zoos, and other protected regions. Also, it protects the illegal trade of wildlife.
Water (Prevention and control of Pollution) Act, 1974
Provides maintenance and restoration and quality of all types of surface and groundwater.
Forest (Conservation) Act,1980
Check deforestation and encourage afforestation of non-forest areas.
The Environment(Protection) Act, 1986
Providing for the protection and improvement of the Environment.
Biological Diversity Act, 2002
To provide for the conservation of biological diversity
National Green Tribunal Act, 2010
Environmental protection and conservation of forests and other natural resources.
India is a tropical country and it has high opportunities for harvesting solar energy using Photovoltaic technology. Photovoltaic is a technology that converts sunlight directly into electricity.
Recently Solar energy became very cheap and many houses in rural and urban areas use them as part of their Primary power consumption. Also, many big power plants are established all over the country by the Union Government, State Government, Private and also through PPP (Public Private Partnership).
Photovoltaic or solar produces a very litter voltage of 0.5–1 V when exposed to sunlight, this is very little. But when these cells are combined in an arrangement that will produce sufficient Current which will be utilized for various applications.
The main advantages of solar cell are they do have any moving parts, as a result, it requires only little maintenance and it has a long life.
The periodical rise and fall of the sea level, once or twice a day, mainly due to the attraction of the sun and the moon, is called a tide. The movement of water caused by meteorological effects (winds and atmospheric pressure changes) are called surges. Surges are not regular like tides. The study of tides … Continue reading “Types of tides Upsc”
The periodical rise and fall of the sea level, once or twice a day, mainly due to the attraction of the sun and the moon, is called a tide.
The movement of water caused by meteorological effects (winds and atmospheric pressure changes) are called surges. Surges are not regular like tides. The study of tides is very complex, spatially and temporally, as it has great variations in frequency, magnitude, and height.
The moon’s gravitational pull to a great extent and to a lesser extent the sun’s gravitational pull, are the major causes for the occurrence of tides.
the lunar portion of Earth’s tides By The SVG code is valid. This vector image was created with Inkscape-default – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15500578
Another factor is centrifugal force, which is the force that acts to counterbalance gravity. Together, the gravitational pull and the centrifugal force are responsible for creating the two major tidal bulges on the earth.
On the side of the earth facing the moon, a tidal bulge occurs while on the opposite side through the gravitational attraction of the moon is less as it is farther away, the centrifugal force causes a tidal bulge on the other side.
The ‘tide generating force is the difference between these two forces; i.e. the gravitational attraction of the moon and the centrifugal force.
On the surface of the earth, nearest the moon, pull or the attractive force of the moon is greater than the centrifugal force, and so there is a net force causing a bulge towards the moon. On the opposite side of the earth, the attractive force is less, as it is farther away from the moon, the centrifugal force is dominant.
Hence, there is a net force away from the moon. It creates the second bulge away from the moon. On the surface of the earth, the horizontal tide generating forces are more important than the vertical forces in generating the tidal bulges.
The tidal bulges on wide continental shelves have greater height. When tidal bulges hit the mid-oceanic islands they become low.
The shape of bays and estuaries along a coastline can also magnify the intensity of tides. Funnel-shaped bays greatly change tidal magnitudes. When the tide is channeled between islands or into bays and estuaries they are called tidal currents.
Types of Tides
Tides vary in frequency, direction, and movement from place to place and also from time to time. Tides may be grouped into various types based on their frequency of occurrence in one day or 24 hours or based on their height.
Tides based on Frequency
Semi-diurnal tide
The most common tidal pattern, featuring two high tides and two low tides each day. The successive high or low tides are approximately the same height.
Diurnal tide
There is only one high tide and one low tide during each day. The successive high and low tides are approximately the same height.
Mixed tide
Tides having variations in height are known as mixed tides. These tides generally occur along the west coast of North America and on many islands of the Pacific Ocean. Tides based on the Sun, Moon, and the Earth Positions.
The height of rising water (high tide) varies appreciably depending upon the position of the sun and moon with respect to the earth. Spring tides and neap tides come under this category.
Tides based on Frequency By User:KVDP, SVG conversion by Surachit – Public domain image: File:Tides schematic.JPG which was based on an image in “Leidraad voor het Stuurbrevet” by Richard Vooren, Paul Van den Keybus, Public Domain, https://commons.wikimedia.org/w/index.php?curid=8752107
Spring tides
The position of both the sun and the moon in relation to the earth has a direct bearing on tide height. When the sun, the moon, and the earth are in a straight line, the height of the tide will be higher.
These are called spring tides and they occur twice a month, one on the full moon period and another during the new moon period.
Neap tides
Normally, there is a seven-day interval between the spring tides and neap tides. At this time the sun and moon are at right angles to each other and the forces of the sun and moon tend to counteract one another.
The Moon’s attraction, though more than twice as strong as the sun’s, is diminished by the counteracting force of the sun’s gravitational pull.
Once in a month, when the moon’s orbit is closest to the earth (perigee), unusually high and low tides occur. During this time the tidal range is greater than normal.
Two weeks later, when the moon is farthest from Earth (apogee), the moon’s gravitational force is limited and the tidal ranges are less than their average heights.
When the earth is closest to the sun (perihelion), around 3rd January each year, tidal ranges are also much greater, with unusually high and unusually low tides. When the earth is farthest from the sun (aphelion), around 4th July each year, tidal ranges are much less than average.
The time between the high tide and low tide, when the water level is falling, is called the ebb. The time between the low tide and high tide, when the tide is rising, is called the flow or flood.
Importance of Tides
Since tides are caused by the earth-moon-sun positions which are known accurately, the tides can be predicted well in advance. This helps the navigators and fishermen plan their activities.
Tidal flows are of great importance in navigation. Tidal heights are very important, especially harbours near rivers and within estuaries having shallow ‘bars’ at the entrance, which prevent ships and boats from entering into the harbour.
Tides are also helpful in desilting the sediments and in removing polluted water from river estuaries. Tides are used to generate electrical power (in Canada, France, Russia, and China). A 3 MW tidal power project at Durgaduani in Sunderbans of West Bengal is underway.
Sea Waves are mostly caused by wind. The wind drive waves are called the surface and are formed by the friction between wind and surface water. When the wind blows across the surface of the ocean, the continuous disturbance forms a wave crest.
These other types of sea waves also are discussed below.
Waves
A wave is a disturbance or change, that transfers the energy progressively from one point in the medium to another point. This disturbance in a medium (sea) carries energy without a net movement of particles. This may take the form of elastic deformation, change in pressure, etc.
In this article, we are going to discuss ‘sea waves, their formation, origin, types etc.
Types of Sea Waves
There are three types of Sea waves. They are distinguished as Wind Waves and Swell, Wind Surges, and Tsunamis (Sea Waves due to Earthquake, volcanic eruption, etc)
Sea waves are further classified based on their wavelength into Capillary Wave, Wind Wave, Seiche, Seismic Sea Wave.
Capillary Wave
Capillary Wave By kallerna – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=88899901
Capillary Wave has a wavelength less than 2 Cm. Its disturbing force is Wind.
Wind Wave
Wind Wave By Brocken Inaglory – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=3379848
Wind Wave has a wavelength between 60 to 150m. This is caused by the wind over the sea.
Seiche Wave
Seiche Wave By Buonasera – Rechteinhaber und eigenes Foto, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17820532
Seiche Wave has a Wavelength that is large than Wind Wave, it changes to a great extent and is in order of the basin size. This is caused by disturbing forces such as Storm surge, Change in atmospheric pressure, etc.
Tsunami or Seismic Wave
Tsunami or Seismic Wave By David Rydevik (email: david.rydevikgmail.com), Stockholm, Sweden. – Originally at Bild:Davidsvågfoto.JPG., Public Domain, https://commons.wikimedia.org/w/index.php?curid=177627
Tsunami Wave has a typical wavelength of about 200 Km. This type of wave is caused by a volcanic eruption, landslide, earthquake. faulting of the seafloor.
Sea Waves
The waves are energy that moves across the ocean’s surface. The water particles travel in a small circle when the wave passes by.
Mostly, this energy is triggered by the wind and makes the waves travel, making this energy released on the seashores. The Waves on the surface of the ocean and their motion affects the deepwater of oceans that are stagnant.
The waves get slow down when reaching the beach. This is due to friction between the seafloor and the dynamic water. The wave breaks when the depth of the water is less than half of the wavelength of the wave.
Open oceans are home to the largest waves. The waves grow in size as they move and absorb energy from the wind.
Wind Wave Formation
Most of the waves are formed due to wind driving against the water. When a breeze of two knots or fewer blows over the calm water, small ripples were created and grow as the speed of the breeze increased. This wave grows until the white caps appear in the breaking waves.
The sea wave travels thousand of miles before rolling ashore, breaking and dissolving as surf.
Wave Size and Origin
The origin of a wave can be determined by the size of the wave. Steep waves are young waves that are probably formed due to the local wings.
But the steady and slow waves may have formed from far away places, maybe or even from another Hemisphere.
Height of Wave
The maximum wave height is determined by the strength of the wind. But how long the wind blows and the area over which the wind blows in a single direction determines the wave height.
Waves travel because the wind pushes the water body in its course. But gravity pulls the crests of the waves downward. The falling water pushes the former troughs upward, and the wave moves to a new position.
The actual motion of the water below the waves is circular. This indicates that things are carried up and forward as the wave approaches, and down and back as it passes.
Characteristics of Waves
Wave crest and trough
The highest and lowest points of a wave are called the crest and trough respectively.
Wave height
It is the vertical distance from the bottom of a trough to the top of a crest of a wave.
Wave amplitude
It is one-half of the wave height.
Wave period
It is merely the time interval between two successive wave crests or troughs as they pass a fixed point.
Characteristics of Waves – Height, Crest, Wavelength, amplitude, trough By Kraaiennest – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4038226
Wavelength
It is the horizontal distance between two successive crests.
Wave speed
It is the rate at which the wave moves through the water, and is measured in knots.
Wave frequency
It is the number of waves passing a given point during a second time interval.
Conclusion
The waves are basically of four types. The winds are the main cause of the sea waves. The other causes are earthquakes, volcano eruptions, landslides, etc. Also based on the size of the wave its origin can be determined.
The ocean water is dynamic. Its movements are influenced by Physical characteristics and external forces.
Causes of ocean water movement such as Waves, Tides, and Ocean Currents are Temperature, salinity, density, and external forces such as sun, moon, and winds.
Difference between waves tides and ocean currents
Difference between waves tides and ocean currents By World Wide Gifts – Peru – Paracas National ReserveUploaded by snowmanradio, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=28224008
There are two types of movement in Ocean water are Horizontal and Vertical motion. Ocean current and waves are Horizontal movements and Tides are vertical motion.
The ocean currents are the continuous flow of a large amount of water in a particular direction. The water moves ahead from one place to another in case of ocean currents.
On the other hand, Waves are a horizontal movement of water, where the water does not move. But in the case of wave train the moves ahead. The vertical motion refers to the rise and fall of the ocean and seawater due to the attraction of the moon and sun.
This vertical motion will happen twice a day. Another type of vertical movement is caused by the upwelling of cold water from subsurface and surface water sinking.
Waves Tides and Ocean Currents are the types of movement of ocean water.
The latitude and longitude coordinates of India are 20.5937° N, 78.9629° E.
What is latitude and longitude?
Latitude and longitude are a set of lines used to describe the location of any place on earth. The Earth is not a perfect sphere its polar radius and equatorial radius are not the same. There is bulging at the equator because of the earth’s rotation over its axis.
Therefore the shape of the earth is not a perfect sphere and it actually looks like an Oblate Spheroid. Because of its shape, there are difficulties in positioning its surface features and there is no point of reference from which to measure the relative positions of other points.
Therefore a set of lines is drawn on the map or globe to mark reference of the location of a different place on the earth’s surface. The basis of the geographical grid, formed by two natural points of reference is the North and South Pole.
The earth spins from west to east. The latitudes and longitudes are sets of horizontal and vertical lines.
The Horizontal lines are called Parallels of latitudes and Vertical lines are called the meridians of longitudes.
Longitudes
A set of vertical lines that join the North and South Poles are called the Meridians of Longitude. These lines converge at the poles and far apart at the equator.
Longitudes of India
India’s longitudinal extent spans from 68°7’E to 97°25’E, covering a significant east-west distance. This longitudinal stretch has several implications for India.
This longitudinal stretch has several implications for India:
Time Zones
The large longitudinal extent could theoretically result in a time difference of up to 2 hours between the easternmost and westernmost points of the country. However, to maintain uniformity, India adheres to a single time zone, Indian Standard Time (IST), based on the 82.5° East longitude.
Sunrise and Sunset
Due to the longitudinal spread, the sun rises earlier in the eastern parts of India compared to the western regions. This variation in sunrise and sunset times influences daily routines and activities across the country.
Climate
The longitudinal extent can contribute to regional variations in climate, particularly in terms of monsoon patterns and temperature differences. The eastern and western coastal regions, for example, experience distinct climatic conditions due to their exposure to different ocean currents and wind systems.
Agricultural Seasons
The varying day lengths and solar radiation across different longitudes can impact the timing of agricultural seasons. Farmers in different regions may adopt different cropping patterns and irrigation practices to optimize their agricultural activities based on the local climatic conditions influenced by longitude.
Latitudes
These lines are drawn parallel to each other in an east-west direction and the Latitude at which the earth is divided into two halves is called the Equator. The equator is also called the Great Circle, as it is the largest circle and divides the globe into two halves.
Other lines of latitudes are called Small Circle, as they are smaller than the Great Circle, and get smaller and smaller toward the poles and divide the earth into two unequal halves. All these lines of latitudes, including the Great Circle and Small Circle, are called parallels of latitude.
Latitudes of India
India’s latitudinal extent ranges from 8°4’N to 37°6’N. This means that the northernmost point of India lies at 37.6 degrees north of the equator, while the southernmost point is 8.4 degrees north.
This latitudinal extent has several implications for India:
Tropical Climate
The Tropic of Cancer, located at 23.5°N, passes through the middle of India. This contributes to the country’s predominantly tropical climate, characterized by hot and humid summers and mild winters.
Diverse Topography
India’s latitudinal extent results in a diverse range of landscapes, from the snow-capped Himalayas in the north to the tropical rainforests in the south.
Monsoon Patterns
The latitudinal position of India influences the country’s monsoon system. The seasonal reversal of winds brings rainfall to different parts of the country at different times.
Conclusion
The latitudes and longitudes are generally called Geographical coordinates because they provide a systematic network of the line by the which position of different surface characteristics of the Earth can be represented.
In the globe or map, an infinite number of Longitudes and latitudes can be drawn but only a selected number of lines are generally drawn. It is measured in degrees (°) as it represents Angular distances. Then each degree is further divided into 60 minutes ( ‘ ) and each minute into 60 seconds ( “ ).
The measurement of the degree of hotness or coldness of ocean water is referred to as ocean temperature. Temperature is normally measured in the units of degrees Celsius by thermometers. The major source of heat energy for ocean water is the radiation from the sun. Just like land, the ocean’s water gets heated up by solar energy but the process of heating and cooling the ocean is slower compared to the land.
Factors affecting ocean temperature
1.Latitude
The solar radiation at different latitudes is different, and thus, the temperature is different. The global distribution pattern of sea temperature is progressive decrease from low latitude sea areas to high latitude sea areas.
As the amount of insolation decreases poleward, the temperature of surface water decreases from the equator towards the poles. The temperature of surface water between 40°N and 40°S is lower than air temperature but it becomes higher than air temperature between 40th latitude and the poles in both the hemispheres.
2.Unequal distribution of land and water
In the northern hemisphere, the oceans there receive more heat due to their contact with a larger extent of land whereas the ocean in the southern hemisphere receives less heat because of comparatively less contact with land than the northern hemisphere.
The isotherms are not regular and do not follow latitudes in the northern hemisphere becauses of the existence of both warm and cold landmassess whereas isotherms are regular and follow latitudes in the southern hemisphere becuase of the dominance of water.
The temperature in the enclosed seas in low latitudes becomes higher because of the influence of surrounding land areas than the open seas e.g., the average annual temperature of surface water at the equator is 26.7°C whereas it is 37.8° in the Red Sea and 34.4°C in the Persian Gulf.
3.Prevailing wind
Wind direction largely affects the distribution of temperature of ocean water.
The winds blowing from the land, flow towards the oceans or sea (e.g., offshore winds) driving the warm surface water away from the coast and resulting in the upwelling of cold water from below due to this, it results in longitudinal variation in the temperature.
On the other hand, the onshore winds that are winds blowing the oceans, pile up warm water near the coast and this raises the temperature.
For example, trade winds cause low temperature (in the tropics along the eastern margins of the oceans or the western coastal regions of the continents) because they blow from the land towards the oceans whereas these trade winds raise the temperature in the western margins of the oceans or the eastern coastal areas of the continents because of their onshore position.
Similarly, the eastern margins of the oceans in the middle latitudes (Western coasts of Europe and North America) have relatively higher temperature than the western margins of the oceans because of the onshore position of the westerlies.
4.Ocean Currents
In sea areas at the same latitude, the temperature of sea water where warm current flow is higher and the temperature of sea water where cold currents flow lower.
That is ocean plays an important role as the warm ocean currents raise the temperature in a colder area and the cold currents decrease the temperature in warm ocean areas.
Example
1.The Gulfstream which is a warm current raises the temperature near the eastern coast of North America and the West Coast of Europe.
2.The Labrador Current which is a cold current decrease the temperature close to the northeast coast of North America.
3.Kuro Shivo drives warm water away from the eastern coast of Asia and raises the temperature near Alaska.
Similarly, the temperature of the eastern coast of Siberia becomes low due to Kurile cool current. It may be mentioned that warm currents raise the temperature more in the northern hemisphere than in the southern hemisphere which is apparent from the face that the 5°C isotherm reaches 70° latitude in the northern Atlantic Ocean whereas it is extended upto only 50° latitude in the southern Atlantic ocean.
This is because of more dominant effects of the warm Brazil current in the southern Atlantic ocean.
Temperature of ocean water
5.Season
Sea temperature is high in the summer and low in the winter.
6.Depth
The progressive decrease in temperature is significant as the depth of the surface sea water increases, with variations being more obvious within 1000m. There is less variation from 1000 meters to 2000 meters, and low temperature is maintained all year at depths below 2000m.
The above factor highly influences the temperature of ocean currents locally.
7.Minor Factors
Minor factors include
1. Submarine ridges
2. Local weather conditions like storms, cyclones, hurrincanes, fog, clodiness, evaporation and condensation.
3.location and shape of the sea.
Longitudinally more extensive seas in the low latitudes have higher temperature than the latitudinally more extensive seas as the Mediterranean. Sea records higher temperature than the Gulf of California.
The enclosed seas in the low latitudes record relatively higher temperature than the open seas Example Mediterranean Sea, Red Sea, etc. whereas the enclosed seas have lower temperature that the open seas in the high latitudes. Example: North Sea, Baltic Sea 0°C and open seas have 4.4°C.
Horizontal and Vertical Distribution of Temperature
The temperature decrease as the depth increases can be seen by the temperature-depth profile of the Ocean Water and this profile shows the boundary region between the deep layers of ocean water and the surface waters.
This boundary starts around 100-400 m below the sea surface and extends up to several meters deep this boundary from where there is a rapid decrease of temperature is called the Thermocline and about 90% of the total volume of water is found below the Thermocline and also in this region, the temperature approaches 0° C (Approx).
The temperature structure of the oceans over the middle and low latitudes can be explained by a three-layer system from the surface to the bottom
Three-layer systems from the surface to bottom are:
First Layer
The first layer is the top layer which has Warm Oceanic Water and its thickness is about 500m with temperature that ranges from 20° and 25° C (Approx). The first layer is present within the tropical region and is present throughout the year in midlatitudes and it develops only during the Summer Season.
Second Layer
The Thermocline which is the Second layer lies below the first layer or top layer which has warm oceanic water. The Thermocline layer or second layer is characterized by a rapid decrease in temperature as the depth increases and the thickness of this layer is 500 – 1000m.
Third or Last Layer
The last layer is very cold and it is the third layer. It extends up to the deep ocean floor. In the Arctic and Antarctic circles, the oceanic water’s surface temperature is close to 0° C (Approx) and the temperature variation with the depth is very low. This is because here there is only one layer of cold water that extends from the surface to the ocean floor at the deep.
The average temperature of the surface oceanic water is around 27°C (Approx) and it gradually decreases from the equator towards the poles.
The rate of decrease of temperature with increase in latitude is commonly 0.5°C (Approx) per latitude and the average temperature of oceanic water is around 22°C (Approx) at 20° latitudes, 14 °C (Approx) at 40° latitudes and 0° C (Approx) near poles.
In comparison, the temperature of the ocean water in the Northern Hemisphere is higher than in the Southern Hemisphere. Also, the Highest temperature of the ocean water is recorded in the North of the equator, not at the equator. The average annual temperatures of the Northern Hemisphere are 19° C (Approx) and the Southern Hemisphere 16° C (Approx) respectively.
This difference in temperature is due to the unequal distribution of land and water in the North and South hemispheres. As already said, the maximum temperature of ocean water is at the surface, the top layer because it is exposed to direct sunlight and the lower layers get the heat by the process of convection and this is the reason for the decrease in temperature with depth.
But this decrease in temperature is uniform, and it decreases rapidly up to the depth of 200m and then, the rate of decrease in temperature is slow.
FAQ
What is the temperature of deep ocean water?
There is great change at greater depths, there is a temperature that ranges from around 30 °C(Approx) at the sea surface to −1 °C(Approx) at the seabed (bottom of the sea). The deep ocean for example below 200 meters is cold and its average temperature is only 4°C(Approx). Also, cold water is more dense than warm water.
How does water temperature change with depth?
Ocean water gets colder with depth, as only the top layer of water gets heat by sunlight and the layer below it gets heat by convection also the heat generated per square meter of Earth is very small to make ocean water warm. Also, the salty water stays at the bottom, which gets colder than less salty water which stays on the top layer.
How cold is the water at the bottom of the ocean?
The average temperature at the bottom is −1°C to 4°C (Approx).
Why is seawater warmer at night?
The heat absorbed by the top layer of water is mixed with the lower layer of water and as the top layer loses its temperature during the night it gets warm from the underneath layer and also lands gets cool faster than the water.
Does salinity increase with depth?
Yes, the salinity increases with depth because salty water is dense and heavier which stays low and the less salty water is less dense and stays on top. The halocline is the layer, where the salinity changes rapidly with depth.
Can oceans freeze?
Ocean water freezes at -2°C because of salt in it, as the normal water freezers at 0°C.
What part of the sea is the coldest?
The bottom of the Antarctic Ocean is the coldest of all and also it greatly influences the movements of water in other oceans.
It is an imaginary line dividing the surface of the Earth, which runs from the North Pole to the South Pole and demarcates the border between one calendar day and the next. It serves as the “line of demarcation” between the two calendar days.
International Date Line on world map
As seen on the world map below, the International Date Line runs north and south across the middle of the Pacific Ocean. The date line does not follow the meridian exactly. It bends once to the west and once to the east. The actual date line passes through the middle of the Bering Strait, then it turns to the southwest until it reaches the middle of 170° east longitude. As shown in the image below.
World map showing international date line
As shown in the International Date Line on the world map above, we see that the Aleutian Islands are all on the American side of the line, and it sweeps eastward again to the 180th meridian, which it follows to the Fiji Islands.
International date line on map By Another Matt (talk) – I (Another Matt (talk)) created this work entirely by myself, incorporating a map from http://commons.wikimedia.org/wiki/File:Blankmap-ao-090N-north_pole.png, which is stated to be public domain, CC0, https://en.wikipedia.org/w/index.php?curid=34272122
As shown in the International Date Line on world map above, we see that the Aleutian Islands are all on the American side of the line, and it sweeps eastward again to the 180th meridian, which it follows to the Fiji Islands. As these Islands, and many other small islands in these regions below to Great Britain and are politically connected with Australia and New Zealand politically connected with Great Britain, the line swings again to the east, giving the British possession the same calendar day.
After this deflection, the International Date Line returns to the 180th meridian, which passes through the frozen regions of the Antarctic Ocean.
Aleutian islands international date line map
International Date Line for Ships
A ship sailing eastward, when crossing the date line, always drops a day out of its calendar. It is because the ship passes from the region of the new day into that of the day before.
For this reason, a ship sailing westward while crossing the date line adds another day. Since the ship leaves the region of the day it was in and enters the region of the new day.
Example 1: The ship crosses the date line eastward on Monday, dropping the day out of its calendar and going back to Sunday again.
Example 2: When the ship crosses westward on Monday, the ship immediately takes up the next day ahead or Tuesday.
This is how the International Date Line on world map is important for sailing and helps in determining the date during a sea voyage.
International Date Line and its coordinates
Latitude: 0° 00′ 0.00″ N
Longitude: -180° 00′ 0.00″ W
international date line world map labeled
How does the international date line work?
The curious thing that brought out this date line is the fact that the total duration or life of each day. When you consider the entire globle and not just a single locality, a day is 48 hours instead of 24 hours.
For example, imagine a person close to
Prime meridian
Is the Prime Meridian and the International Date Line the same thing?
The Prime Meridian separates the Eastern Hemisphere from the Western Hemisphere. International Date Line is halfway around the world, at 180-degree Longitude. The Prime Meridian is present at 0 degrees Longitude.
What is the time difference between the IDL and the Prime Meridian?
The time difference between the International Date Line and the Prime Meridian is 12 Hours.
IDL Latitude and longitude
It passes through the Mid-Pacific Ocean and follows a 180-degree longitude North-South Line.
Location
It is located halfway around the world from the Prime Meridian. The zero-degree longitude is present or established in Greenwich, England in 1852.
International date line passes through
International Date Line passes through which countries?
It passes through Samoa, Tokelau, Wallis and Futuna, Fiji, Tonga, Tuvalu, and New Zealand. The Kermadec Islands and the Chatham Islands are all west of the IDL and have the same date.
American Samoa, Cook Islands, Niue, and French Polynesia are located east of IDL and one day behind.
International Date Line passes through which strait?
It passes at 180 degrees of longitude, but it bends eastward through the Bering Strait. It does so to avoid dividing Siberia and then bends westward to include the Aleutian Islands with Alaska.
Bering Strait International Date Line
International date line time zone
UTC−12:00 is an identifier for a time offset from UTC of −12:00. It is the last to enter a new year and is sometimes referred to as the International Date Line West time zone (IDLW).
Diomede Islands in the International Date Line
International date line and Arctic Circle
The Arctic circle is close to 16,000 km and the area north of the Circle is roughly 20,000,000 km2 which covers almost 4% of Earth’s Surface.
The Arctic is derived from the word “arktikos”, which means bear in the Greek language. The “Ursa Major” Constellation is viewed in the Northern sky. The Arctic Circle region, where at least 1 day a year will receive sunshine all day during summer and the full one day or 24 will not receive any light and will be dark throughout the day.
The Arctic Circle passes through the Arctic Ocean, the Scandinavian Peninsula, North Asia, North America, and Greenland.
The countries in the Arctic Circle are eight; they are Norway, Sweden, Finland, Russia, the United States, Canada, Denmark, and Iceland.
IDL also separates Russia and the US off Alaska’s West Coast.
The Big Diomede Islands in Russia and Little Diomede in the USA are apart by 3.8 Km of the sea, and IDL runs midway between them.
The Arctic and Antarctic Circles are the parallels of latitude that are roughly 66.5 degrees (66° 33′ 44″ (or 66.5622°).
Arctic circle latitude
Arctic Circle, parallel, or line of latitude around the Earth, at approximately 66°30′ N. This is due to the Earth’s inclination of about 23 1/2° to the vertical. This marks the southern limit of the area within which, for one day or more each year.
As a result, the Sun does not set (about June 21) or rise (about December 21).
FAQ
a. Where is the dateline located?
The dateline is located at the 0-degree longitude line in Greenwich, England. It was established in 1884 and passes through the mid-Pacific Ocean.
b.What is the longitude of the International Date Line?
It is 0-degree Longitude. It is the starting point.
c. Antarctic circle passes through which countries?
The only country that passes through the Antarctic Circle is Antarctica. But Antarctica is not a country; it is the southernmost continent.
Most famous volcanoes in Iceland is Eyjafjallajokull because of its eruption in 2010. Other famous volcanoes are Katla, Öræfajökull, Bárðarbunga etc.
Mount Hekla has erupted 18 times, the last time it erupted was in 2000.
Iceland volcanoes names
Iceland has a large concentration of active volcanoes, as it is located on the Mid-Atlantic Ridge, a divergent tectonic plate boundary.
It has over 30 active volcanic systems and each volcano’s tectonic fissure systems and most of them also stratovolcano, shield volcanoes. The most active volcano in this region is Grímsvötn.
Below is the list of the most famous volcanoes in Iceland.
Volcanoes in Iceland facts
There are around 130 volcanoes in Iceland. The reason behind such a high number of volcanoes is its location. As this Iceland nation lies where two tectonic plates meet.
As the two tectonic plates are not fused, an extremely hot substance known as lava rises from inside.
Fagradalsfjall
Fagradalsfjall volcano is part of the Krýsuvík-Trölladyngja volcanic system on the Reykjanes Peninsula in southwest Iceland.
Katla volcano
It is one of the largest volcanoes in Iceland. It is situated to the north of Vík í Mýrdal and to the east of the smaller glacier Eyjafjallajökull.
Grímsvötn
It is located in Vatnajökull National Park, Iceland. Grímsvötn, a subglacial volcano, is located 140 km NE of Eyjafjallajökull volcano within the western region of the Vatnajökull glacier. It is a type of Caldera.
Hekla
Hecla, is a stratovolcano in the south of Iceland with a height of 1,491 m (4,892 ft). Hekla is one of Iceland’s most active volcanoes. It is the most famous and active volcano in the country.
Askja
It is an active volcano, situated in the remote part of the central highlands. The most recent eruption was in 1961. It is a type of basaltic.
Snæfellsjökull
Snæfellsjökull is a 700,000-year-old glacier-capped stratovolcano in western Iceland. It is situated in the most western part of the Snæfellsnes peninsula. It is present in the West Iceland glaciers.
Volcanic Areas in Iceland – By Volcanic_system_of_Iceland-Map-fr.svg: Pinpinderivative work: Chris.urs-o (talk) – Volcanic_system_of_Iceland-Map-fr.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=9877884
Eldfell
Eldfell is a volcanic cone just over 200 metres (660 ft) high on the Icelandic island of Heimaey. Eldfell is a volcano in the Westman Islands, off the South Coast of Iceland, which famously erupted in the middle of the town of Heimaey in 1973.
Öræfajökull
It is an ice-covered volcano in southeast Iceland. Its type is Stratovolcano. It is shaped like a cone, with a large ice-filled caldera, and is 600-700 m deep. It has erupted twice once in 1362 and the other in 1728.
Eldgjá
It is situated in Landmannalaugar and Kirkjubæjarklaustur. Eldgjá is the largest volcanic canyon in the world, approx. It is an example of a shield volcano.
Hengill
It is situated in the southwest of Iceland, which is south of Þingvellir. It is a mountain that covers an area of 100 square kilometres. Geothermal energy is produced, which is a vital source of energy for south Iceland.
Torfajökull
It is a rhyolitic stratovolcano, caldera, and a complex sub-glacial which is located north of Mýrdalsjökull and south of Þórisvatn Lake. It last erupted in March 1477.
Vatnafjöll
Vatnafjöll is a 40 km (25 mi) long, 9 km (6 mi) wide basaltic fissure vent system that is located southeast of Hekla, Iceland. It last erupted 1200 years ago.
Esjufjöll
Esjufjöll is a small volcanic system and as such part of Iceland’s Oræfi Volcanic Belt. The subglacial Esjufjöll volcano located at the SE part of the Vatnajökull icecap, north of Öraefajökull, consists of the Snaehetta central volcano and a large caldera.
Ljósufjöll
Ljósufjöll is a fissure vent system and central volcano on the Snæfellsnes Peninsula in Iceland. The system has a length of about 90 km. It last erupted in 960 CE.
Prestahnúkur
The volcano Prestahnúkur is located in the west of the Highlands of Iceland to the west of Langjökull glacier.
Grímsnes
Grímsnes is a fissure or crater row volcanic system located in South Iceland, a relatively small volcanic system located SE of Thingvallavatn lake east of an en-echelon group of volcanic sites extending across the Reykjanes Peninsula.
It last erupted in May 2011.
Herðubreið
Herðubreið is a tuya in the northern part of Vatnajökull National Park, Iceland. It is situated in the Highlands of Iceland on the east side of the Ódáðahraun desert and close to Askja Volcano.
Kerlingarfjöll
It is part of a tuya volcano system of 100 sq. km. It has numerous hot springs. It is glacially dissected.
Hverfjall
Hverfjall also known as Hverfell is a tephra cone or tuff ring volcano in northern Iceland. Last erupted in 2500 BP.
Theistareykjarbunga
Theistareykjarbunga is a shield volcano in northeastern Iceland with two fissure vents called Theistareykjahraun and Borgahraun. It last erupted in 900 BC.
Kollóttadyngja
Kollóttadyngja is a shield volcano in the Ódáðahraun lava field in Iceland. Its height is 1,177 metres, and it has a diameter of 6–7 km.
Bláhnjúkur
Bláhnjúkur is a volcano in the south of Iceland. Its height is 940 m.
Trölladyngja
Trölladyngja is the biggest of the Icelandic shield volcanoes, reaching a height of 1,468 metres (4,816 ft) above sea level.
Helgafell
Helgafell is an inactive 227-meter-high volcanic cone located on the island of Heimaey in the Vestmannaeyjar archipelago in Iceland.
Búrfell
Búrfell is a 480 m (1,570 ft) basalt tuya located in Iceland.
Brennisteinsalda
The Brennisteinsalda is a volcano in the south of Iceland. Its height is about 855 m. It is situated near Landmannalaugar and not far from Hekla.
Conclusion
Iceland has around 130 volcanoes, and mostly it has stratovolcanos, which is a cone-shaped peaks. Also, there are shield volcanoes.
The ocean has great depression features. The oceans are similar to continents that merge into one another and it is difficult to demarcate them. The oceans are divided by Geographers as Pacific, Atlantic, Indian, Southern Ocean, and the Arctic. These oceans consist of various seas, bays, gulfs, and other inlets.
A major part of the ocean floor is found between 3-6 km below sea level. The land under the ocean is the ocean floor which shows complex and different characteristics similar to those variants on the land. The Bottom relief features of the Ocean Floor consist of rugged mountain chains, ranges, deepest trenches, and large plains.
These relief features are formed similar to continents by tectonic, volcanic, and deposition processes.
Relief of the ocean floor
Division of Bottom relief features of Ocean
The ocean floor is divided into:
Continental Shelf
Continental Slope
Deep Sea Plain
Oceanic Deeps
Apart from the above four major divisions, there are also minor divisions such as Ridges, hills, sea, mounts, guyots, trenches, canyons, etc.
Continental Shelf
It is the extended margin of every continent that is occupied mostly by shallow seas and gulfs. The continental shelf is the shallowest part of the ocean and shows an average gradient of 1° or even less. The continental shelf mostly ends at a very steep slope called the shelf break. The width of the continental slope differs from one ocean to another and its average width is around 80 km.
The continental shelves are mostly absent or very narrow along the coasts of Chile, the west coast of Sumatra, etc. On the other hand, the Siberian shelf in the Arctic Ocean is the largest in the world and stretches about 1500 km in width.
The depth of the continental shelf also differs, it might be as shallow as 30m or as deep as 600m. These shelves are covered with different thicknesses of sediments which are carried down by wind, rivers, glaciers, etc and distributed by waves and currents.
These massive deposits on shelves over a long period of time have become the source of fossil fuels.
Continental Slope
It connects the continental shelf and the ocean basins. The continental slope starts where the bottom of the continental shelf sharply drops into a steep slope.
The gradient of the slope region varies between 2-5°. The depth of the continental slope is between 200 to 3000 metre. The boundary of the slope indicates the end of the continents and also Canyons and trenches are found in these regions.
Deep-Sea Plain
These plains are gently sloping areas of the ocean basins and these are the flattest and smoothest regions of the world. Its depth varies from 3000 to 6000 m. The deep-sea plains are covered with fine-grained sediments such as clay and silt.
Oceanic Deeps or Trenches
Trenches are the deepest parts of the oceans. It is relatively steep-sided and has narrow basins. It is also 3-5 km deeper than the surrounding ocean floor. The trenches are found at the base of continental slopes, near island areas, and are related to active volcanoes and earthquakes.
As of now, 57 trenches have been found and out of them, 32 are found in the Pacific, 19 found in the Atlantic, and 6 in the Indian Ocean.
Minor Bottom relief features of Ocean
Mid Oceanic Ridge
It is two chains of mountains that are separated by a huge depression. These mountain ranges can be as high as 2500 m and some stay at ocean level. Iceland is part of the mid-Atlantic Ridge.
Seamount
Seamount is a mountain with pointed summits that rises from the seafloor and does not reach the surface of the ocean. These are of volcanic origin, their height is around 300-4500 m.
Example: the Hawaiian Islands in the Pacific Ocean
Submarine Canyons
Submarine Canyons are deep valleys similar to the Grand Canyon. These are commonly found across the continental slopes and shelves.
Hudson Canyon, Public domain, via Wikimedia Commons
Example: Hudson Canyon
Guyots
Guyots are flat-topped seamounts. This shows pieces of evidence of gradual subsidence through stages to become a flat-topped submerged mountain.
It is estimated that there are 10,000 Guyots in the Pacific Ocean.
Atoll
The atoll is a low island seen in the tropical ocean consisting of coral reefs surrounding a central depression.
Atoll – Source: Atafu.jpg: NASA Johnson Space Center
These might be part of the sea lagoon or forms enclosing a body of fresh, brackish, or saline water.
Conclusion
This article is written for the topic ‘Ocean bottom relief features’ for Upsc and state service exams. This article includes the Continental Shelf, Continental Slope, Deep Sea Plain, Oceanic Deeps, and other minor ocean reliefs.
* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.
