VI NCERT Geo Gist – MAPS

  • A MAP is a representation or a drawing of the earth’s surface or a part of it drawn on a flat surface according to a scale. Maps are of different types.
  • Physical maps : Maps showing natural features of the earth such as mountains, plateaus, plains, rivers, oceans etc. are called physical or relief maps.
  • Political maps: Maps showing cities, towns and villages, and different countries and states of the world with their boundaries are called political maps.
  • Thematic maps: Some maps focus on specific information; such as road maps, rainfall maps, maps showing distribution of forests, industries etc. are known as thematic maps.
  • There are three components of maps – distance, direction and symbol.
  • A Scale is the ratio between the actual distance on the ground and the distance shown on the map.
  • When large areas like continents or countries are to be shown on a paper, then small scale is used. It is called a small scale map.
  • When a small area like village or town is to be shown on a paper, then large scale is used. It is called a large scale map.

#     Large scale maps give more information than small scale maps.

  • The directions on the map are North, South, East and West. They are called Cardinal points. The direction of a place can be found out with the help of a
  • Conventional symbols are used to show different features on a map.
  • A Sketch is a rough drawing which is drawn without a scale, and this is called a sketch map.
  • A plan is a drawing of a small area on a large scale. These are drawings drawn to a scale.
Advertisements

VI NCERT Geo Gist – Motions of the Earth

Rotation:

  • The earth has two types of motions, namely rotation and revolution.
  • Rotation is the movement of the earth on its axis.
  • The movement of the earth around the sun in a fixed path or orbit is called Revolution.
  • The axis of the earth which is an imaginary line, makes an angle of 66 1/2o with its orbital plane. The plane formed by the orbit is known as the orbital plane.
  • The circle that divides the day from night on the globe is called the circle of illumination. This circle does not coincide with the axis.
  • The earth takes about 24 hours to complete on rotation around its axis. The period of rotation is known as the earthday. This is the daily motion of the earth.

What would happen if the earth did not rotate?

The portion of the earth facing the sun would always experience day, thus bringing continuous warmth to the region. The other half would remain in darkness and be freezing cold all the time. Life would not have been possible in such extreme conditions.

Revolution:

  • It takes 365 ¼ days (one year) to revolve around the sun.
  • A year is usually divided into summer, winter, spring and autumn seasons.
  • Seasons change due to the change in the position of the earth around the sun.
  • The longest day and the shortest night at Tropic of Cancer occur on 21st At this time in the Southern Hemisphere all these conditions are reversed. It is winter season there. The nights are longer than the days. This position of the earth is called the Summer Solstice.
  • On 22nd December, the Tropic of Capricorn receives direct rays of the sun as the South Pole tilts towards it. As the sun’s rays fall vertically at the Tropic of Capricorn, a larger portion of the Southern Hemisphere gets light. Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights. The reverse happens in Northern Hemisphere. This position of the earth is called the Winter Solstice.
  • On 21st March and September 23rd, direct rays of the sun fall on the equator. At this position, neither of the pole is tilted towards the sun; so, the whole earth experiences equal days and equal nights. This is called an equinox.

Hence, there are days and nights and changes in the seasons because of the rotation and revolution of the earth respectively.

VI NCERT Geo Gist – Latitudes and Longitudes

  • An imaginary line passing through the North and South poles of the earth is called the axis
  • Another imaginary line running on the earth 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.
  • All parallel circles from the equator up the poles are called parallels or latitudes. Latitudes are measured in degrees.
  • The equator represents the zero degree latitude.
  • 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’ and south are called ‘south latitudes’.

Important Parallels of Latitudes:

Besides the equator (0o), the North Pole (90oN) and the South Pole (90oS), there are four important parallels of latitudes –

  • Tropic of Cancer (23oN) in the Northern Hemisphere.
  • Tropic of Capricorn (23oS) in the Southern Hemisphere
  • Arctic Circle at 66o north of the equator
  • Antarctic Circle at 66o south of the equator

Heat Zones of the Earth:

Torrid Zone: the mid-day sun is exactly overhead atleast 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

Temperate Zones: 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.

Frigid 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 and provide less heat. These are, therefore, called Frigid Zones (very cold).

Longitudes:

To locate places precisely, one 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 meridians of longitude, and 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.

Unlike parallels of latitude, all meridians are of equal length. The meridian which passes through Greenwich, where the British Royal Observatory is located is called the Prime Meridian. Its value is 0o longitude and from it we count 180o eastward as well as westward. The prime meridian and 180o meridian divide the earth into two equal halves, the Eastern Hemisphere and the Western Hemisphere. The 180o East and 180o West meridians are on the same line.

Why do we have standard time?

  • The local time of places which are on different meridians are bound to differ. It is, therefore, necessary to adopt the local time of some central meridian of a country as the standard time for the country.
  • In India, the longitude of 82o30’ E is treated as the standard meridian. The local time at this meridian is taken as the standard time for the whole country. It is known as the Indian Standard Time (IST)
  • Some countries have a great longitudinal extent and so they have adopted more than one standard time. For example, in Russia, there are as many as eleven standard times.
  • The earth has been divided into 24 time zones of one hour each. Each zone covers 15o of longitude.

VI NCERT Geo Gist – The Earth in the Solar System

  • The sun, the moon and all those objects shining in the night sky are called celestial bodies
  • The celestial bodies which have their own heat and light, which they emit in large amounts are called stars
  • Different groups of stars are called constellations. Ex: Ursa Major or Big Bear
  • One of the most easily recognizable constellation is the small bear or the Saptarishi, a part of the Ursa Major constellation
  • The North Star or the Pole Star indicates the north direction. It always remain in the same position in the sky
  • Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called Planets.
  • The word ‘Planet’ comes from the Greek word “Planetai” which means ‘wanderers’.

The Solar System:

The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.

  • The sun is about 150 million km away from the earth.

Planets:

  • There are eight planets in our solar system. In order of their distance from the sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
  • Mercury is nearest to the sun. Takes only about 88 days to complete one revolution
  • Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.
  • ‘Pluto’ may be called a ‘dwarf planet’.

The Earth:

  • The earth is the third nearest planet to the sun.
  • In size, it is the fifth largest planet.
  • It is slightly flattened at the poles. That is why, its shape is described as a Geoid.
  • The earth is a unique planet as it has life-supporting conditions like water, air and oxygen.
  • Earth is called a blue planet as its two-thirds surface is covered by water.

The Moon:

  • The earth has only one satellite, that is, the moon.
  • It’s diameter is only one-quarter that of the earth.
  • It is about 3,84,400 km away from the earth.
  • The moon moves around the earth in about 27 days. It takes exactly the same time to complete one spin.

Satellites:

  • A Satellite is a celestial body that moves around the planets in the same way as the planets move around the sun.
  • A Human-made Satellite is an artificial body. It is designed by scientists to gather information about the universe or for communication. Some of the Indian satellites in space are INSAT, IRS, EDUSAT etc.

Asteroids:

Apart from the stars, planets and satellites, there are numerous tiny bodies which also move around the sun. These bodies are called asteroids. They are found between the orbits of Mars and Jupiter.

Meteoroids:

The small pieces of rocks which move around the sun are called meteoroids.

Galaxy:

A galaxy is a huge system of billions of stars, and clouds of dust and gases. There are millions of such galaxies that make the Universe. Our solar system is a part of the Milky Way galaxy.