⛪Home⇐ Class Earth Movements and Seasons


Mind Maps
 
IV_SOC_Means_of_Transport/
IV_SOC_Northern_Plains/
III_SCI_Pollution/
IX_TS_Soc_tsNatural_Earth/
VII_SOC_When_Where_How/
IX_Soc_Nazism_Rise_Hitler2/
 
 


Class - : Array
One Word Answer Questions:
Q) What is the highest Mountain range on the Earth?
A)    Show/hide Answer

Q) Which animal is found in the desert?
A)    Show/hide Answer

Q) What is the low land called that lies between mountains or hills called?
    
A)    Show/hide Answer

Q) What type of trees are grown in Costal areas?
    
A)    Show/hide Answer

Q) The Largest part of our area is covered with what?
    
A)    Show/hide Answer

Short Answer Questions:
Q) What is a Desert?
A)   Show/hide Answer

Q) What is land?
A)   Show/hide Answer

Q) Describe our Earth?
A)   Show/hide Answer

Q) What are Mountains?
A)   Show/hide Answer

Q) What is a Forest?
A)   Show/hide Answer



Introduction
  • Human beings live along with a large community of plants and animals.
  • We can observe constant change in our surroundings in the course of the year - the flowering and fruiting of trees and plants, changes the animal activity etc.
  • As months pass by, you would notice that trees shed leaves, stand bare, new shoots come forth, leaves grew again, they flower and give fruits.
  • You may also have noticed that it different times of the year, we get different kinds of vegetables and fruits. In some months, it is very hot and in some, it is cold or wet.
Earth Movements

  • Observe the picture given below carefully
  • Do you know why these changes happen? Yes that’s right, these are due to different seasons.
  • Have you ever seen your surroundings covered by snow? You may have seen it flooded by water during rains but never snow.
  • Some parts of the earth get so cold during some months that they get snowfall instead.
  • This picture is taken in Ohio in USA. It snows heavily in the Northern countries during winter;
  • in summer months, it is not so cold but still much cooler than in our state. However, the funny thing is that in those countries, the day is much longer in summer so much so that you can see the Sun even at midnight!
  • Find out the name of the country that is called the ‘land of midnight Sun’ and locate it on the globe.
  • Find out its latitude and compare it with the latitude of Telangana. Locate Australia, South Africa and Chile on the globe.
  • These are also called the countries of the Southern Continents, that is continents that are located to the South of the Equator.
  • In these countries, the cycle of seasons is different. They have winter when we have summer and when we have winter, they have summer! In fact, this is the pattern in all the places to the south of the Equator.
  • You are not the only ones with such questions. For thousands of years human beings have been curious about these matters and over time, have worked out the answers.
  • Let us try to understand why seasons change, why are some parts of the earth warm and some cold and why are the seasons opposite in the Northern and Southern hemispheres.
Factors Effects the seasons

To understand these, we have to understand the complex interaction between several factors. These are:

  1. The spherical shape of the Earth and the curvature of its surface.
  2. Daily rotation of the Earth on its own Axis.
  3. The tilt of the Axis of rotation compared to the plane on which the Earth moves.
  4. The Earth’s movement around the Sun once a year (revolution).
  1. Curvature of the Earth
    • You have already studied the impact of the spherical shape of the Earth and how this causes distribution of heat over the Earth’s surface differently, how the region around the Equator becomes warmer than those near the Poles.
  2. Earth’s Rotation on its Axis
    • The Earth rotates or goes around just like a ‘top’ spins. What does it go around?
    • It actually rotates around an imaginary line which joins the North Pole and the South Pole. This line is called the Axis of the Earth’s rotation.
    • All parts of the earth go around this line once a day.
    • In other words, the Earth takes about 24 hours to rotate or go around its own axis.
    • It moves from the west to the east if a globe is facing you it rotates from your left to the right side. You can see that the Western portion moves towards the east.
    • This is the reason why the Sun, the Moon and the stars appear to rise in the east and set in the west.
    • This is, of course, an illusion created by the eastward spin of Earth.
    • The first and foremost effect of earth’s rotation is the daily alternation of day and night, as portions of Earth’s surface are turned first toward and then away from the Sun.
    • This variation in the exposure to sunlight greatly influences the local temperature and wind movements.
    Earth Movements

    • Similarly, the Sun illuminates one-half of the earth at any given movement.
    • The edge of the sun-lit hemisphere, called the circle of illumination, is a great circle that divides the earth between a light half and a dark half.
    • What would happen if the earth did not rotate on its own axis?
    • Then, one portion of the earth which is in front of the Sun would constantly get Sun’s heat and light and the other portion would remain cold and dark.
    • This would make both portions unfit for life the bright half would be too hot and the dark half would be too cold.
    • Thus, rotation helps the entire earth to get heat and light consistently on a daily basis.
  3. Earth's ‘Tilt’ and Revolution Around the Sun
  • The earth revolves around the Sun while rotating around its own axis. That is, it spins like a top and at the same time, keeps moving forward around the Sun.
  • The motion of the earth around the Sun is called ‘revolution’.
  • Each revolution takes about 365 days and 5.56 hours. This is the length of a year on the Earth.
  • How does this cause the formation of seasons on the Earth?
  • Had the Earth just gone around the Sun it would have meant that a place would have had the same seasons throughout the year.
  • The portions that get more sunshine would keep getting it throughout the year in the same way and the vice-versa.
  • But this is not so, because the Axis of Earth’s rotation is inclined (slanting) and points in the same direction throughout the year.
  • What do we mean by ‘inclined axis’?
  • The earth goes around the Sun on a regular path (also called Orbit) on a level plane in open space.
  • This is called the Orbital PlanePpng" alt="Earth Movements"
  • rection throughout the year. It keeps pointing to the Pole star (which can be seen in the Northern sky in the night) and this is called the Polarity of Axis.
  • In the pictures, you can see what happens when the Earth goes around the Sun in this manner.
  • During some months (June) the Northern Hemisphere is tilted.


Earth Movements
Earth Movements

Temperature Belts on the Earth
  • Let us see how the effect of the tilt of the Axis combines with the spherical shape of the Earth to influence distribution of solar heat over the Earth. We saw earlier that when the solar rays strike the Earth’s surface, they fall straight in portions which face the Sun directly and fall at an angle as you move away from that portion.
  • The angle keeps increasing as we move towards the two Poles. As a result it is hotter in the areas which face the Sun directly and less hot in the areas that receive the Sun rays at an angle.
  • As a result of the tilt of the axis, the area which faces the Sun directly keeps shifting throughout the year. In March, the Sun shines directly over the Equator, while in June, it shines directly over the Tropic of Cancer in the Northern Hemisphere.
  • Then, in September, as the Earth travels further around the Sun, the Sun shines directly over the Equator. In December, it shines over the Tropic of Capricorn in the Southern Hemisphere. Thus, you can see that there is a belt within which the direct rays of the Sun fall at some time of the year or the other. This belt extending from the Tropic of Cancer to the Tropic of Capricorn is called the Tropical Belt.
  • This belt gets the maximum heat energy from the Sun. June 21 – Sun on the Tropic of Cancer March 21, Sept. 23 – Sun on the Equator December 22 – Sun on the Tropic of Capricorn On March 21 and September 23 throughout the world, the day and night are equal in size, so these are called equinoxes.
  • As we move northwards or southwards of the Tropical Belt, we reach a region where it gets warm in summers but also very cold in winters. This is the Temperate Zone. The northern portions of this region get snowfall in winters.
  • If you move further north or south of the Temperate Belt, you will reach the Polar Region. The seasons in this region are very peculiar. This region is away from the Sun during winter months and does not get any sunshine in the day!
  • That is, for six months there is no Sunshine on the Poles. For the next six months, it constantly faces the Sun throughout the 24 hours of a day there is no night or darkness!
  • A place which has six months of day and six months of night! Even during the ‘day’, it gets very slanting rays of the Sun.The Sun does not rise high in the sky but only stays just above the sunrise point (also called the horizon).
  • So it never gets very hot. So, for six months it is freezing cold so cold that an entire ocean the Arctic Ocean remains frozen throughout the year. So cold that the soil becomes frozen like a hard rock and roots of trees can’t penetrate them.
  • So trees just can’t grow in this region. When the Sun appears for six months, the snow melts, part of the sea also melts. Small plants like moss, lichen and some flowering plants grow.
Earth Movements
- Facebook | - Twitter | - Google+ | - YouTube | - Mail
Meritpath...Way to Success!

Meritpath provides well organized smart e-learning study material with balanced passive and participatory teaching methodology. Meritpath is on-line e-learning education portal with dynamic interactive hands on sessions and worksheets.