Wednesday, March 13, 2013

GLOBE : LATITUDES AND LONGITUDES

Globes may be of varying size and type – big ones,
which cannot be carried easily, small pocket globes,
and globe-like balloons, which can be inflated and are
handy and carried with ease. The globe is not fixed. It
can be rotated the same way as a top spin or a potter’s
wheel is rotated. On the globe, countries, continents
and oceans are shown in their correct size.
It is difficult to describe the location of a point on a
sphere like the earth. Now the question arises as to
how to locate a place on it? We need certain points of
reference and lines to find out the location of places.
You will notice that a needle is fixed through the
globe in a tilted manner, which is called its
axis
. Two
points on the globe through which the needle passes
are two poles – North Pole and South Pole. The globe
can be moved around this needle from west to east
just as the earth moves. But, remember there is a major
difference. The real earth has no such needle. It moves
around its axis, which is an imaginary line.
Another imaginary line running on the globe divides
it into two equal parts. This line is known as the
equator
. The northern half of the earth is known as
the Northern Hemisphere and the southern half is
known as the Southern Hemisphere. They are both
equal halves. Therefore, the equator is an
imaginary circular line and is a very
important reference point to locate places
on the earth. All parallel circles from the
equator up to the poles are called
parallels
of latitudes
. Latitudes are measured in
degrees.

The equator represents the zero degree
latitude. Since the distance from the
equator to either of the poles is one-fourth
of a circle round the earth, it will measure
¼
th of 360 degrees, i.e. 90°. Thus, 90
degrees north latitude marks the North
Pole and 90 degrees south latitude marks
the South Pole.

As such, all parallels north of the
equator are called ‘north latitudes.’
Similarly all parallels south of the equator are called
‘south latitudes.’
The value of each latitude is, therefore, followed by
either the word north or south. Generally, this is
indicated by the letter ‘N’ or ‘S’. For example, both
Chandrapur in Maharashtra (India) and Belo
Horizonte in Brazil (South America) are located on
parallels of about 20° latitude. But the former is 20°
north of the equator and the latter is 20° south of it.
We, therefore, say that Chandrapur is
situated at 20° N latitude and Belo
Horizonte is situated at 20° S latitude.
We see in Figure 2.2 that as we move
away from the equator, the size of the
parallels of latitude decreases.



I
MPORTANT PARALLELS OF LATITUDES
Besides the equator (0°), the North Pole
(90°N) and the South Pole (90° S), there
are four important parallels of latitudes–
(i)
Tropic of Cancer (23½° N) in the
Northern Hemisphere. (ii)
Tropic of
Capricorn
(23½° S) in the Southern
Hemisphere. (iii)
Arctic Circle at 66½°
north of the equator. (iv)
AntarcticCircle
at 66½° south of the equator.

H
EAT ZONES OF THE EARTH
The mid-day sun is exactly overhead at
least once a year on all latitudes in
between the Tropic of Cancer and the
Tropic of Capricorn. This area, therefore,
receives the maximum heat and is called
the
Torrid Zone.
The mid-day sun never shines
overhead on any latitude beyond the
Tropic of Cancer and the Tropic of
Capricorn. The angle of the sun’s rays
goes on decreasing towards the poles. As
such, the areas bounded by the Tropic
of Cancer and the Arctic Circle in the
Northern Hemisphere, and the Tropic of
Capricorn and the Antarctic Circle in the
Southern Hemisphere, have moderate
temperatures. These are, therefore, called
Temperate Zones
.
Areas lying between the Arctic Circle
and the North Pole in the Northern
Hemisphere and the Antarctic Circle and
the South Pole in the Southern
Hemisphere, are very cold. It is because
here the sun does not rise much above
the horizon. Therefore, its rays are
always slanting. These are, therefore,
called
Frigid Zones.
W
HAT ARE LONGITUDES?
To fix the position of a place, it is
necessary to know something more
than the latitude of that place. You
can see, for example, that Hyderabad
(in Pakistan) and Allahabad (in India)
are situated on the same latitude (i.e.,
25°25
'N). Now, in order to locate them
precisely, we must find out how far
east or west these places are from a
given line of reference running from
the North Pole to the South Pole.
These lines of references are called the
distances between them are measured in ‘degrees of
longitude.’ Each degree is further divided into minutes,
and minutes into seconds. They are semi-circles and
the distance between them decreases steadily polewards
until it becomes zero at the poles, where all the
meridians meet.
meridians of longitude, and the

Sunday, March 3, 2013

INDIA : CLIMATE, VEGETATION AND WILDLIFE

You read in newspapers daily and watch on T.V. or
hear others talking about weather. You must know
that weather is about day to day changes in the
atmosphere. It includes changes in temperature,
rainfall and sunshine etc. For example, as such it may
be hot or cold; sunny or cloudy; windy or calm. You
must have noticed that when it is hot continued for
several days you don’t need any warm clothing. You
also like to eat or drink cold things. In contrast there
are days together, you feel cold without woollen clothes
when it is very windy and chilly, you would like to
have something hot to eat.
Broadly, the major seasons recognised in India are:
• Cold Weather Season (Winter) December to
February
• Hot Weather Season (Summer) March to May
• Southwest Monsoon Season (Rainy)
June to September
• Season of Retreating Monsoon (Autumn) October
and November

COLD WEATHER SEASON OR WINTER


During the winter season, cool, dry winds blow from
north to the south. The sun rays do not fall directly in
the region as a result, the temperatures are quite low
in northern India.

HOT WEATHER SEASON OR SUMMER

In the hot weather season sun rays more or less directly
fall in this region. Temperature becomes very high.
Hot and dry winds called loo, blow during the day.



SOUTH WEST MONSOON SEASON OR RAINY SEASON

This season is marked by the onset and advance of
monsoon. The winds blow from Arabian Sea and Bay
of Bengal towards the land. They carry moisture with
them. When these winds strike the mountain barriers,
rainfall occurs.

SEASON OF RETREATING MONSOONS OR AUTUMN

Winds move back from the mainland to the Bay of
Bengal. This is the season of the retreating monsoons.
The southern parts of India, particularly Tamil Nadu
and Andhra Pradesh receive rainfall in this season.
However, the climate is about the average weather
condition, which have been measured over many years.
The climate of India has broadly been described as
Monsoon type. Monsoon is taken from the Arabic word
‘mausim’, which means seasons. Due to India’s location
in the tropical region, most of the rain is brought by
monsoon winds. Agriculture in India is dependent on
rains. Good monsoons mean adequate rain and a
bountiful crop.



The climate of a place is affected by its location,
altitude, distance from the sea, and relief. Therefore,
we experience regional differences in the climate of
India. Jaisalmer and Bikaner in the desert of Rajasthan
are very hot, while Drass and Kargil in Jammu and
Kashmir are freezing cold. Coastal places like Mumbai
and Kolkata experience moderate climate. They are
neither too hot nor too cold. Being on the
coast, these places are very humid.
Mawsynram in Meghalaya receives the
world’s highest rainfall, while in a
particular year it might not rain at all in
Jaisalmer in Rajasthan.

NATURAL VEGETATION

We see a variety of plant life in our
surroundings. How nice it is to play in a
field with green grasses. There are also
small plants called bushes and shrubs like
cactus and flowering plants etc. Besides
there are many tall trees some with many
branches and leaves like neem, mango or
some which stand with few leaves such as
palm. The grasses, shrubs and trees, which
grow on their own without interference or
help from human beings are called natural
vegetation. Do you wonder how these differ
from each other. Different types of natural
vegetation are dependent on different
climatic conditions, among which the
amount of rainfall is very important.
Due to varied climatic conditions, India
has a wide range of natural vegetation.
Vegetation of India can be divided into five
types – Tropical evergreen forest, Tropical
deciduous forest, Thorny bushes,
Mountain vegetation and Mangrove
forests.

TROPICAL RAIN FOREST

Tropical Rain Forests occur in the areas
which receive heavy rainfall. They are so
dense that sunlight doesn’t reach the ground.
Many species of trees are found in these forests,
which shed their leaves at different times of the year. As a result, they always appear green and are
called evergreen forest look at the Figure 8.1.
Important trees found in these forests are
mahogany, ebony and rosewood. Andaman and
Nicobar Islands, parts of North-Eastern states and
a narrow strip of the Western slope of the Western
Ghats are home of these forests.





TROPICAL DECIDUOUS FORESTS
In a large part of our country we have this type of
forest. These forests are also called monsoon forests.
They are less dense. They shed their leaves at a
particular time of the year. Important trees of these
forests are sal, teak, peepal, neem and shisham. They
are found in Madhya Pradesh, Uttar Pradesh, Bihar,
Jharkhand, Chhattisgarh, Orissa, and in parts of
Maharashtra.

THORNY BUSHES