OCEANS AND SEAS, Some landforms Associated with water Bodies

Some landforms Associated with water Bodies

i)      Sea

        The part of ocean adjacent to the continental margins is called sea, i.e. Arabian Sea and red sea etc.

ii)     Gulf

        A large but narrow part of ocean which invades farther inland is called Gulf, i.e. Persian Gulf and Gulf of Mexico etc.

iii)    Bay

        Contrary to gulf, large and vast part of ocean which invades farther inland is called bay, i.e. Bay of Bengal and Hudson bay etc.

iv)    Bight

        A very vast and extended bay is called bight, i.e. Great Australian Bight in the South Australia.

v)     Strait

        An narrow passage of water which connects two large bodies of water i.e. oceans or seas e.g. Strait of Gibraltar which connects Atlantic ocean with Mediterranean sea.

vi)    Peninsula

        An area of land which is surrounded by ocean water from their sides except for an isthmus which connects it with connects it with the mainland is called peninsula i.e. Arabian and Indian peninsula.

vii)   Island

        An area of land surrounded by water from all sides is called an island, i.e. Srilanka, Indonesia and West Indies, etc.

viii)  Isthmus

        A narrow strip of land which connects two large masses of land is called an isthmus, i.e. is thymus of Panama which connects North and South American continents and the Isthmus of Suez connects Asia with Africa.

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OCEANS AND SEAS

Oceans and seas

        The largest body of water on the surface of earth is called Ocean and an adjacent smaller body of water on the surface of earth is called Ocean and an adjacent smaller body of water is called sea. There are five oceans in the word. These are. Pacific Ocean, Atlantic Ocean, Indian Ocean, Antarctic Ocean, Arctic Ocean

i)      Pacific Ocean

        It is the largest ocean. Its area is 155 million square kilometers and it stretches over 17000 kilometers in width. It has an average depth of 4000 meters. It marginal areas are comprised of deep trenches and volcanoes. Panama Canal which links Pacific Ocean with the Atlantic is among the important trade routes of the world.

ii)     Atlantic Ocean

        It is the second largest ocean. Its area is 76 million square kilometers and it has an average depth of 3900 meters. Mid- oceanic ridge, which is the result of eruption of magma at the divergent plate boundary, is the significant feature of this ocean. This oceanic ridge spreads across the Atlantic, Indian, pacific and Antarctic Ocean over 60,000 kilometers in length. It is included in the active earthquake areas of the world. It is also the world’s most important and busiest trade route.

iii)    Indian Ocean

        It is the third largest ocean. Its area is about 68 million square kilometers and has an average depth of 3900 meters. It has maximum stretch in southern hemisphere. Mid-oceanic ridge from the Atlantic Ocean also divides the floor of Indian Ocean in East-West portions. Deep trenches are also present in which java trench is 7400 meters deep. It has become an important trade route between links red sea (Indian Ocean) with the Mediterranean Sea.

iv)    Antarctic Ocean

        Antarctic Ocean has an area of 20 million square kilometers and an average depth of 4000 meters. It has no distinct boundary with the pacific, Atlantic and Indian Ocean. Extreme cold water and huge icebergs are characteristic features of this ocean.

v)     Arctic Ocean

        Arctic Ocean is situated around the North Pole. It has an area of 14 million square kilometers and an average depth of 1200 meters. Shallow waters, low salinity and frozen surface are characteristic features of this ocean.

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Agents of landforms change

Agents of landforms change

Landforms

          Different types of landforms are found on our earth because its surface is not uniform. These landforms have been created by internal and external forces of the earth-Mountains, plateaus and plains etc. are the major landforms created by the internal forces of the earth. External forces of the earth include different agents which create different landforms in different environments by erosion and deposition. These agents are river, glacier, wind and sea waves etc.

          Let us have a look on landforms created by these agents.

Landforms Made by River

          River is an important agent of landform change. Permanent rivers are found in those areas which receive ample rainfall regularly presence of mountains provides initial slope for the flow of surface water in tiny channels. These tiny channels join to form a river. A river after its creation performs three types of geologic work. It breaks the rocks coming in its way. This act is called Erosion. It transports the eroded material. This act is called Transportation. It deposits the eroded material when its speed is very low. This act is called deposition.

1. River’s Emotional landforms

          In mountains the valley of the river gets deeper due to downward erosion and attains the shape of English alphabet ‘V’. This landform is called V-Shaped valley. Very deep valleys are often called ‘Gorges or canyons’. Such valleys are found in northern areas of Pakistan.

2. Water fall

          River bed may contain hard and soft rocks. Sometimes soft rocks are found beneath hard rocks. When the river cuts the upper layer of hard rocks on the ved, it tends to erode the lower hard rocks to a great depth. This results in the creation of water fall.

3.      Pot Holes

          Sometimes the swirling action of stones in the water develops holes in the river bed. These are called potholes.

4.      Meanders and ox-bow lake

          Occurrence of hard and soft rocks in the river’s channel results in the creation of a winding path due to uneven erosion of the river. These are called meanders. Sometimes river after cutting the outer bends of the meanders attains a straighter channel, leaving behind a crescent lake at the side. This lake is called Ox- bow lake. Kalery lake on river Indus is an ox-bow lake.

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Methods of showing statistical data i) line Graph ii) Bar Graph iii) Pie Graph

Methods of showing statistical data

          In geography, diagrams are those conceptual sketches through which geography information and data is transferred to the paper. These are called statistical diagrams. These are.

          Line graph            Bar Graph            Pie graph

Let us study these diagrams in detail.

1.      Line graph

          In this diagram, statistical data is displayed with help of a line on the graph, therefore it is called line graph. In this graph two variables are shown, one as variable quantity and other as a constant. To construct a line graph, two lines are drawn meeting each other at 90 degrees. Horizontal line is called X-Axis (Rain, years, Distances etc.) and measureable variable is placed on Y-Axis (Rain, Temperature, air pressure, production etc.) To measure the values at Y-Axis, an appropriate scale is determined. With the help of scale, values are marked in the form of dots for each constant variable. Then these dots are joined by a line to prepare a line graph.

Merits of line graph

          With the help of line graph more than one variables can be compared easily, i-e we can compare the annual temperatures and rainfall values or Karachi and Lahore, which is not possible on bar and pie graph. Due to this property of line graph, it is preferred over bar graph.

Line graph is the best way to show decrease or increase in annual, monthly and daily productions of various items. Besides this, line graph is also used to show weather conditions, population, animal distribution, exports and imports of a country. All these statistics are related to time, so these are better illustrated on a line graph.

One line graph, we can easily understand the fluctuations as well as the production of items.

Demerits of line graph

          Although we can show average quantities and productions on line graph, we can not show percentages on it. Percentages are better shown on pie graphs.

Although we can show fluctuations in productions, we can not show total production of any item on the line graph, i-e total annual rainfall of a place or total population of country.

2. Bar graph

          Bar Graph is widely in geography. In this graph, we show quantities in the form of bars of equal width on equal intervals. The height of the bar varies with quantity. Bars can be drawn both vertically and horizontally. This method is very useful for comparison of different quantities, i-e population of big cities of Pakistan, length of canals, marks of students in a subject, imports and exports of country, areas and productions etc. We can also shade and colour the bars.

Merits of Bar graph

·         We can show total quantity of production on the bar graph.

·         We can also compare different quantities of the same item.

·         It is easy to show quantities on bar graph.

Demerits of Bar graph

·         To show more than one item or quantity, we have to draw multiple bars or a compound bar

·         It is possible to show value of only one item on the bar graph.

·         We cannot show percentages on bar graph.

3. Pie Graph

     Sometimes geographical data is displayed in circles or sectors of circle, i-e population or areas of a country or cities, imports or exports, trade and percentages on it. When we have to show quantities of same type in percentages, the circle is supposed to be divided in 100 parts and sectors are created with the help of following formula.

                                                                            

     We can calculate the specific angle (Sector of the circle) of the given percentage by another formula.

                                     

     These sectors can be shaded or colored.

Merits of pie graph

·         Pie graph covers less space as compared to line and bar graph. It presents a better comparison between different quantities. We can also show the total quantity on this graph.

·         It shows the areas of different countries in a better way which is not possible on line and bar graph. Pie graph is preferred to show production of power resources, i-e electricity gas.

Demerits of pie graph

·         Pie graph is not suitable to show weather data, i.e., distribution of temperature, rain and wind pressure.

Calculations of percentages and division of circle into sectors are comparatively difficult and consuming.

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