Water: Ocean

Water: Ocean

Learning Goals:

• Ocean Waves
• Tsunami
• Tides

Ocean circulation: 

Unlike the calm waters of a pond or lakes, ocean water keeps moving continuously. These movements can be classified into:

·        Waves

·        Currents

·        Tides

Wave :

·        When the water on the surface of the ocean rises and falls alternately, they are called waves.

·        They are formed when winds scrape the ocean floor.

·        When we throw a ball in the ocean, it gets washed back to the shore by the waves.

·        The stronger the wind blows, the bigger the wave becomes.

·        During a storm, the wind blows at a very high speed forming huge waves.

·        These may cause tremendous destruction.\

·        The following can shift large amounts of ocean water:

• An earthquake
• A volcanic eruption
• Underwater landslide

Due to the above, a huge tidal wave called tsunami is formed. It may be as high as 15 metres. The highest tsunami ever measured was 150 m high. These waves travel at a speed of 700 km/h.

Tides : (prlms 2015)

·        The rhythmic rise and fall of water twice in a day is called a tide.

High Tide: 

·        This occurs when water covers much of the shore by rising to its highest level.

Low Tide:

·        There is a low tide when water falls to its lowest level and recedes from the shore.

·        Tides are caused by the strong gravitational pull exerted by the sun and the moon on the earth’s surface.

·        The rise and fall of water due to tides is used for generating electricity in some places.

·        The water of the earth closer to the moon gets pulled under the moon’s gravitational force and causes a high tide.

Types of Tides:

Spring Tides: 

·        During the full moon and new moon days, the sun, the earth and the moon are in the same line and the tides are the highest.

·        These tides are called spring tides.

Neap Tide: 

·        When the moon is in its first and third quarters, the ocean waters get drawn in diagonally opposite directions by the gravitational pull of the sun and the earth.

·        This results in low tides; called neap tides.

Advantages of High Tide:

·        They help in navigation. They raise the water level close to the shores and help the ships to arrive at the harbor more easily.

·        They help in fishing. More fish come closer to the shore during high tides. This helps the fishermen to have a good catch and earn more.

Ocean Current

·        They are streams of water flowing continuously on the ocean’s surface in definite directions.

·        They influence the temperature conditions of the area. They may be warm or cold.

Warm Current: 

·        They originate near the equator and move towards the poles. The Gulf Stream is a warm current.

·        They bring warm temperature over land surface.

Cold Current: 

·        They carry water from polar or higher latitudes to tropical or lower latitudes. For example; the Labrador Ocean Current.

·         They result in cold temperature over the land surface.

Effect of the meeting of warm and cold currents: (prlms 2013)

• They provide the best fishing grounds of the world.
•  Some example of these are: Seas around Japan and Seas around the eastern coast of North America.
• They lead to foggy weather which makes navigation difficult.

Tsunami

·        Tsunami or the harbor wave brought large scale destruction in the Indian Ocean on 26 December 2004.

·        It was due to an earthquake of magnitude 9.0 on the Richter scale.

·        The epicenter of this earthquake was near the western boundary of Sumatra.

·        There was a sudden movement of sea floor causing earthquake, as the Indian plate went under the Burma plate.

·        The ocean floor was displaced by about 10 to 20 m and huge mass of ocean water filled the gap that was created by the displacement.

·        Tsunami travelled at a high speed of about 800 km/h.

·        The Indira Point in the Andaman and Nicobar Islands got submerged after the tsunami.

·        Some of the islands in the Indian Ocean got completely washed away.

·        The destruction killed more than 10000 people and affected more than one lakh houses.

·         Coastal areas of Andhra Pradesh, Tamil Nadu, Kerala, Puducherry and the Andaman and Nicobar Islands were the worst affected areas in India.

·        Early warning systems are in place which can give a warning of tsunami three to four hour in advance.

·        Such warning systems were in place in the Pacific Ocean but not in the Indian Ocean because tsunamis are rare in the Indian Ocean.

·        The first indication that tsunami is approaching is the rapid withdrawal of water from the coastal region, followed by a destructive wave.

Keywords

Terrarium: It is the artificial enclosure for keeping small house plants.

Salinity: It is the amount of salt in grams present in 1000 grams of water.

Do You Know?

• The average salinity of the ocean is 35 parts per thousand. Dead Sea in Israel has salinity of 45 parts per thousand. Swimmers can float in it because the increased salt content makes it dense.
• World Water Day is celebrated on March 22. On this day the need for conservation of water is reinforced.
• Tsunami is a Japanese word. It means the ‘harbor waves’ as the harbors get destroyed whenever there is a tsunami.

Petroleum and Natural gas in india

Petroleum:

·        It provides lubricants and raw materials for a number of chemical industries.

·         Products include kerosene, diesel, petrol, aviation-fuel, synthetic rubber, synthetic-fibre, thermoplastic resins, benzene-methansol, polystertene, acrylates, detergents, aromatics, gasoline, carbon-black, dyes, colours, food-colours, pigments, explosives, printing ink, film-photography, greases, cosmetics, paints, lubricant oils, paraffin, and wax.

·        Crude oil is obtained mainly from the sedimentary rocks of marine origin. In India, crude oil is found in the sedimentary rocks of the Tertiary period 

.

·         Normally it does not occur at its place of formation.

·        Being lighter than water, crude oil overlain with gas, gets accumulated in the anticlines above the water surface.

In India, origin:

·        1860- mergherita (upper assam) – first time oil discovered by assam railway and trading company .

·        1889- oil was discovered in digboy .

·        1917 – badarpur(assam)  .

·        1954- production of oil was started in naharkatiya region.

·        1956- ONGC .

·        1961- gulf of cambay (khambat) –discovered by ONGC .

·        1976 –bombay high - discovered by ONGC .

 In India, the petroleum and natural gas has been discovered in the following ten basins:

·        1. The Upper Assam Basin (60,000 sq km)

·        2. The Western Bengal Basin (60,000 sq km)

·        3. The Western Himalayan Basin (100,000 sq km)

·        4. The Rajasthan Saurashtra-Kachchh Basin (95,000 sq km)

·        5. The Northern Gujarat Basin (140,000 sq km)

·        6. The Ganga Valley Basin (385,000 sq km)

·        7. The Coastal Tamil Nadu, Andhra & Kerala Basin (75,000 sq km)

·        8. The Andaman and Nicobar Coastal Basin (2000 sq km)

·        9. Offshore of the Khambat, Bombay High & Bassein (2000 sq km)

Crude-Oil Producing Regions in India  :

1. The Western Coast Offshore Oilfields

The Bombay High Oilfields :

·        largest petroleum production oilfield contributing over 65 per cent of the total production of crude oil.

·        lies about 176 km to the south-west of Bombay.

·        has about 35 million tonnes of crude oil and about 40,000 million cubic metres of natural gas.

·        started in 1976.

·        Owing to over exploitation, the production of this oil-field is declining fast.

Bassein Oilfield:

·        lies to the south of Bombay High.

·        occurs at a depth of over 1900 metres.

·        rich deposits of oil and natural gas.

Aliabet Oilfield :

·        located about 45 km to the south of Bhavnagar.

2. The Gujarat Coast

·        This is the second largest oil producing area of the country.

·        Its main oilfields are in Ankleshwar, Cambay-Luni area and Ahmadabad-Kalol region.

 (i) Ankleshwar:

·        Situated in the district of Bharauch, it stretches over an area of about 30 sq km.

·        The oil of this region belongs to the Eocene period.

·        started in 1961.

·        rich in gasoline and kerosene.

·        The crude oil from this region is sent to the Koyali petroleum refinery.

 (ii) Cambay-Luni Region:

·        lies about 60 km to the west of Vadodara.

·        started in 1958.

·        The estimated reserves of crude-oil are over 30 million tonnes.

·        very light with a sulphur content of less than 0.1 per cent.

(iii) The Ahmadabad-Kalol Region:

·        lies to the north of Gulf of Khambat (Cambay) around the city of Ahmadabad and extends up to Mehsana. Kalol, situated about 25 km to the north of Ahmadabad is an important oilfield of the region.

·        started in 1961.

·        supplied mainly to the Koyali refinery.

3.The Eastern Coast:

·        Oil-fields Petroleum and natural gas have been discovered in marine delta regions of Mahanadi, Godavari, Krishna, and Kaveri rivers.

·        The Rawa field in the Godavari-Krishna offshore is expected to produce about 3 million tonnes of crude-oil annually.

·        Petroleum has also been discovered in the Kaveri delta.

·        In addition to these, crude oil has been discovered in the Bilaspur Tehsil of Rampur District of Uttar Pradesh, Jawalamukhi area of Punjab, and in the Barmer District of Rajasthan.

·        found on the offshore of Andaman and Nicobar, Gulf of Mannar, Baleshwar coast, Punjab, Haryana and Uttar Pradesh.

4. The Brahmaputra Valley:

·        Crude oil was first discovered in the Brahmaputra valley.

·        spread from the Dehang Basin up to the Surma valley.

·        The main oil producing wells, however, lie in the Dibrugarh and Sibsagar districts of Upper Assam.

·        Some of the important oil producing centres of this region are given below:

 (i) The Digboi Oilfield Stretching over an area of about 15 sq km, the Digboi oilfield is one of the oldest oil-fields of the country.

·        belongs to the Eocene and Miocene periods.

·        There are 85 oil wells in this region.

·        Most of the oil is sent to the refinery of Digboi.

Natural gas :

      

·        Exploration –by- ONGC

·        potential- about 450 billion cubic metres .

·        75%- lies in Bombay High and the bassein oil fields.

·        12%-GJ

·        7%-andhra Pradesh

·        6%- assam

·        Others- TN , HP ,PUNNJAB

·        Largest share of  natural gas is consumed in the production of chemical fertilizer (about-40%).

·        30% - power generation ,

·        10%- L.P.G (cooking gas)

Prehistoric Rock Paintings in India (NCERT)

 Prehistoric period :

·         The distant past when there was no paper or language or the written word, and hence no books or written document, is called as the Prehistoric period.

·         Piecing together of information deduced from old tools, habitat, bones of both animals and human beings and drawings on the cave walls scholars have constructed fairly accurate knowledge about what happened and how people lived in prehistoric times.

·         Paintings and drawings were the oldest art forms practised by human beings to express themselves using the cave wall as their canvas.

Prehistoric Period:

1) Paleolithic Age,

2) Mesolithic Age and

3) Chalcolithic Age

 (1) Paleolithic Age Art

·         The prehistoric period in the early development of human beings is commonly known as the ‘Old Stone Age’ or ‘Palaeolithic Age’.

·         Palaeolithic period can be divided into three phases:
(1) Lower Palaeolithic (2.5 million years-100,000 years ago)
(2) Middle Palaeolithic (300,000-30,000 years ago)
(3) Upper Palaeolithic (40,000-10,000 years ago)

·         We did not get any evidence of paintings from lower or middle palaeolithic age yet.

·         In the Upper Palaeolithic period, we see a proliferation of artistic activities.

·         Subjects of early works confined to simple human figures, human activities, geometric designs and symbols.

·         First discovery of rock paintings in the world was made in India (1867-68) by an Archaeologist,Archibold Carlleyle, twelve years before the discovery of Altamira in Spain (site of oldest rock paintings in the world).

·         In India, remnants of rock paintings have been found on the walls of caves situated in several districts of Madhya Pradesh, Uttar Pradesh, Andhra Pradesh, Telangana, Karnataka, Bihar and Uttarakhand.

·         Some of the examples of sites early rock paintings are Lakhudiyar in Uttarakhand, Kupgallu in Telangana, Piklihal and Tekkalkotta in Karnataka, Bhimbetka and Jogimara in Madhya Pradesh etc.

·         Paintings found here can be divided into three categories: Man, Animal and Geometric symbols.

·         Some of the characteristics of these early paintings are:

1.   Human beings are represented in a stick-like form.

2.   A long-snouted animal, a fox, a multi-legged lizard are main animal motifs in the early paintings (later many animals were drawn).

3.   Wavy lines, rectangular filled geometric designs and a group of dots also can be seen.

4.   Superimposition of paintings – earliest is Black, then red and later White.

·         In the late historic, early historic and Neolithic period the subjects of paintings developed and figures like Bulls, Elephants, Sambhars, Gazelles, Sheep, Horses, styled human beings, tridents and rarely vegetal motifs began to see.

·         The richest paintings are reported from Vindhya range of Madhya Pradesh and their Kaimurean extension into U.P.

·         These hills are fully Palaeolithic and Mesolithic remains.

·         There are two major sites of excellent prehistoric paintings in India:
(1) Bhimbetka Caves, Foothills of Vindhya, Madhya Pradesh.
(2) Jogimara caves, Amarnath, Madhya Pradesh.

Bhimbetka Caves :

·         Continuous occupation of the caves from 100,000 B.C– 1000 A.D

·         Thus, it is considered as an evidence of long cultural continuity.

·         It was discovered in 1957-58.

·         Consists of nearly 400 painted rock shelters in five clusters.

·         One of the oldest paintings in India and the world (Upper palaeolithic).
The features of paintings of three different phases are as follows (even though Bhimbetka contains many paintings of periods later, different from what is explained explained below, as we are dealing with prehistoric period only, we are concluding by these three):

 Upper Palaeolithic Period:

·         Paintings are linear representations, in green and dark red, of huge animal figures, such as Bisons, Tigers, Elephants, Rhinos and Boars beside stick-like human figures.

·         Mostly they are filled with geometric patterns.

·         Green paintings are of dances and red ones of hunters.

(2) Mesolithic period Art:

·         The largest number of paintings belongs to this period.

·         Themes multiply but the paintings are small in size.

·         Hunting scenes predominate .

·         Hunters in groups armed with barbed spears, pointed sticks, arrows and bows.

·         Trap and snares used to catch animals can be seen in some paintings.

·         Mesolithic people loved to point animals.

·         In some pictures, animals are chasing men and in others they are being chased by hunter men.

·         Animals painted in naturalistic style and humans were depicted in a stylistic manner.

·         Women are painted both in nude and clothed.

·         Young and old equally find places in paintings.

·         Community dances provide a common theme.

·         Sort of family life can be seen in some paintings (woman, man and children).

(3) Chalcolithic period Art:

·         Copper age art.

·         The paintings of this period reveal the association, contact and mutual exchange of requirements of the cave dwellers of this area with settled agricultural communities of the Malwa Plateau.

·         Pottery and metal tools can be seen in paintings.

·         Similarities with rock paintings: 

Common motifs (designs/patterns like cross hatched squares, lattices etc)

·         Difference with rock paintings: 

Vividness and vitality of older periods disappear from these paintings.

Some of the general features of Prehistoric paintings (based on the study of Bhimbetka paintings) :

·         Used colours, including various shades of white, yellow, orange, red ochre, purple, brown, green and black.

·         But white and red were their favourite.

·         The paints used by these people were made by grinding various coloured rocks.

·         They got red from haematite (Geru in India).

·         Green prepared from a green coloured rock called Chalcedony.

·         White was probably from Limestone.

·         Some sticky substances such as animal fat or gum or resin from trees may be used while mixing rock powder with water.

·         Brushes were made of plant fibre.

·         It is believed that these colours remained thousands of years because of the chemical reaction of the oxide present on the surface of rocks.

·         Paintings were found both from occupied and unoccupied caves.

·         It means that these paintings were sometimes used also as some sort of signals, warnings etc.

·         Many rock art sites of new painting are painted on top of an older painting.

·         In Bhimbetka, we can see nearly 20 layers of paintings, one on top of another.

·         It shows the gradual development of the human being from period to period.

·         The symbolism is inspiration from nature along with slight spirituality.

·         Expression of ideas through very few drawings (representation of men by the stick like drawings).

·         Use of many geometrical patterns.

·         Scenes were mainly hunting and economic and social life of people.

·         The figure of flora, fauna, human, mythical creatures, carts, chariots etc can be seen.

·         More importance for red and white colours.