Page 32 - Geography for Secondary Schools Student’s Book Form One

Geography for Secondary Schools
Student’s Book Form One

The Earth revolves around the Sun winter, respectively. Spring is a short season
following its orbit. It revolves around the towards summer while autumn is a short
sun in an elliptical path, completing one full season towards winter.
revolution in approximately 365¼ days or Generally, there are four seasons in a year
one year. However, a normal year has 365 which are differentiated by temperature and
days. The fraction days are not counted rainfall characteristics. These seasons are
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every year but are added once in 4 years
to make a leap year of 366 days. The leap summer, autumn, winter and spring. The
year occurs once in every four years, when four seasons are more pronounced in areas
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the month of February has 29 days instead found between latitudes 23½ and 66½
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of 28. The speed of the earth’s revolution is North and South of the equator. Around 0
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about 29.6 kilometres per second which is to 5 North and South of the equator never
estimated from the earth’s travel about 940 experience seasons because throughout the
million Kilometres. year the sun is almost overhead. Therefore,
these areas experience high temperature
and rainfall. However, this part experiences
Effects of the earth’s revolution seasonal variations due to differences in
The revolution of the Earth around the sun relief. The areas between 5 and 23 ½ North
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and tilting on its axis has the following and South of the Equator are characterised
effects: by hot-wet and cold- dry seasons. The
(i) Seasons of the year North Pole (NP) and the South Pole (SP)

A season is the main period of the year are normally very cold throughout the year
with a particular type of weather. Seasons and it is difficult to distinguish the seasons
are caused by the tilt of the earth’s axis and of the year in these regions.
the earth’s revolution around the sun. With In the Northern Hemisphere, summer
respect to the orbital plane or the horizontal months are June, July and August.
plane, the earth’s axis is tilted at an angle of Autumn months are September, October,
66½ . However, with respect to the vertical and November. Winter season occurs in
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plane, the Earth has an axial tilt of 23½ . December, January, and February whereas
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In its revolution around the sun, one of the spring months are March, April and May.
hemispheres is inclined towards the sun at In the Southern Hemisphere, the summer
one period of the year and away from sun months are December, January, and February.
at another period of the year. For example, Autumn occurs in March, April, and May.
in the months of December, January, Winter season in the Southern Hemisphere
and February, the Southern Hemisphere
tilts towards the sun. Thus, it is summer occurs in June, July, and August, whereas,
time. The same months in the Northern spring months are September, October, and
Hemisphere experience winter season November (Figure 3.5). However, due to
because the Northern Hemisphere tilts away the influence of relief and oceans, these
from the sun. Spring and autumn are short seasons do not always occur in the basis
seasonal transitions between summer and of explained sequence.

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