Classwork Exercise and Series (Geography SS1): Rotation of the Earth

Rotation of the Earth

The earth moves or rotates on its axis from west to east. The rotating earth i inclined at an angle of 23¹/₂⁰ along its axis. It takes the earth 24hours (i.e a day) to complete one rotation (ie the earth rotates through 360⁰ in every 24 hour).The rotation of the earth causes day and night; this is why twenty four hours in a day. That is, twelve hours of day light and twelve hours of darkness. This division does not occur at all times in all places. It rotates through 15⁰ in 1 hour or 1⁰ in 4 minutes

Effects of Rotation of the Earth.

1. Day and Night: As the earth rotates, only one part of the earth’s surface facing the sun receives the rays of the sun and experiences daylight (day) while other part of the earth backing the sun’s rays will experience darkness (night)
2. Deflection of winds and ocean current: The rotation of the earth causes winds and ocean current to be deflected to the right of the direction in which they move in the Northern hemisphere and to the left of this direction in the southern hemisphere.
3. Apparent sunrise and sunset: During the rotation of the earth, part of the earth that emerges from the darkness into the rays of the sun experiences sunrise while the part that is moving away from sun’s rays to darkness will experience sunset.
4. Time differences from places to places. The earth rotates through 3600 in every 24hours which means that for every one hour, it passes through 150. Since the earth moves from west to east, it means that every 150, the east is always one hour ahead of time while the west is always one hour behind time.
5. Daily rising and falling of the tides: During rotation of the earth, it results in the rising and falling in the level of water in the seas and oceans. Owing to rotation of the earth, the tide producing forces cause the surface of water to oscillate, resulting in the rising and falling in the level of water in the saes and oceans.
6. Dawn and Twilight: Dawn refers to the brief period between sunrise and full day light while twilight refers to the brief period between sunset and complete darkness. Dawn and twilight which are the result of rotation are caused because; the earth receives diffused or reflected light from sun while it is still below the horizon.

Earth’s movement (revolution and effects)

The earth moves or revolves around the sun on its orbit. The revolving earth is tilted or inclined at an angle of 66¹/₂⁰ to the plane of ecliptic during its revolution. It takes the earth 365¹/₂ days to complete one revolution (ie moves round the sun). The revolution of the earth causes four seasons in a year. The ¼ day or 6 hours is added up every four years to make an extra day in a leap year. A leap year has 366 days while a normal year has 365 days.

Differences between Rotation and Revolution                        

Effects of revolution of the Earth

1. It determines the year: The time taken by the earth t move round the sun (i e complete its orbit) is fixed at 365¹/₄ which make up a year.
2. It causes seasons: In tropical areas like Wes Africa, including Nigeria, there are two seasons – rainy season and dry season. But in temperate region countries, the revolution of the earth causes four seasons – winter, spring, autumn and summer.
3. Changes in seasonal temperature: It is observed that summers are usually warm and bright, while winters are cold and dark in the arctic region. These include:

• During summer, the zenith angle of the sun is higher
• The concentration of the heat over a small area leads to high temperature
• In, winter, the oblique rays of the sun fall faintly over a large area
• The little heat makes the temperature to remain low
• There are twenty four hours of darkness in winter
• Days are longer than night in summer while in winter, nights are longer than day

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