Download Geography Notes PDF: The Earth, Latitude & Longitude from Parmar SSC Fatman + Lucent. Useful for SSC, Railway, WBCS, UPSC, and other competitive exams.

THE EARTH

Shape of Earth

• Shape of Earth is Geoid or Oblate Spheroid (a little flat from top and bottom) and bulged at the centre.

• Reason: Centrifugal force (due to rotation of Earth).

Radius of Earth

• Equatorial radius: 6378 km

• Polar radius: 6357 km

• Mean radius: 6371 km

Circumference of Earth

• Polar: 40,007.863 km

• Equatorial: 40,075 km

• Mean: 40,040 km

• Equatorial speed > Polar speed

• Equatorial radius > Polar radius

• Equatorial circumference > Polar circumference

• (All because the Earth is bulged at the equator and flattened at the poles)

• 23½° N – Tropic of Cancer

Rotation of Earth

• Earth rotates on its own axis from West to East (Anticlockwise).

• One rotation of Earth = 23 hours 56 minutes 4 seconds

• Rotational speed is maximum at the Equator and minimum at the Poles.

• Day and night are caused by the Earth’s rotation on its axis.

Revolution of Earth

• Earth revolves around the Sun in elliptical orbit.

• One revolution = 365 days 6 hours 9 minutes and 9 seconds

• Orbital speed = 29.8 km/sec

• Mercury has the maximum orbital speed.

• Neptune has the minimum orbital speed.

• The Earth’s revolution around the Sun and the tilt of its axis cause the seasons.

Distance of Earth from Sun and Moon

Sun

• The point in a planet’s orbit when it is closest to the Sun is called Perihelion.

• On January 3rd, the Earth is nearest to the Sun (147 million km).

• The point in a planet’s orbit when it is farthest from the Sun is called Aphelion.

• On July 4th, the Earth is farthest from the Sun (152 million km).

Moon

• The point in the Moon’s orbit when it is closest to Earth is called Perigee.

• At Perigee, the Moon appears larger in the sky.

• The point in the Moon’s orbit when it is farthest from Earth is called Apogee.

• At Apogee, the Moon’s tide-raising force is smaller and the tidal ranges are less than average.

Inclination of Earth’s Axis

• Axial inclination = 23½°

• Orbital inclination = 66½°

LATITUDE AND LONGITUDE

Latitude

• They are imaginary horizontal lines on the globe that run from East to West.

• It is the angular distance of a place from the Equator.

• Total latitudes = 181

• Distance between each latitude is same.

• 1° of latitude = 111 km

Important Latitudes

• 0° – Equator (divides Earth into Northern and Southern Hemisphere)

• 23½° N – Tropic of Cancer

• 66½° N – Arctic Circle

• 23½° S – Tropic of Capricorn

• 66½° S – Antarctic Circle

• All parallel circles from the Equator to the Poles are known as Parallels of Latitude.

• Largest latitude: Equator

• Smallest latitude: Poles

Longitude

• They are imaginary vertical lines on the globe that run North to South.

• Distance between each longitude decreases from Equator towards Poles.

• At the Poles it is 0, while it is maximum at the Equator (111.32 km).

• Total longitudes = 360

Important Meridians (Longitudes)

• Prime Meridian = 0° Longitude (passes through Greenwich, London)

• International Date Line = 180° Meridian

• Prime Meridian is also known as International Meridian or Greenwich Meridian.

It passes through:

• Burkina Faso

• Spain

• France

• Ghana

• Algeria

• Mali

• Togo

• United Kingdom (UK)

Trick to Remember

BSF GAme in TOGO KINGDOM

Concept of Time Using Longitude

• 360° = 24 hours

• 15° = 1 hour

• 1° = 4 minutes

• Earth rotates 15° in 1 hour.

• Earth rotates 1° in 4 minutes.

• Moving East from Prime Meridian, time increases by 1 hour for every 15°.

• Moving West from Prime Meridian, time decreases by 1 hour for every 15°.

Time Zones

• Entire Earth is divided into 24 Time Zones.

• France has the most number of Time Zones (13).

• Russia has 11 Time Zones.

• USA has 6 Time Zones.

Isochrones

• Lines joining points located at equal travel time from a common centre.

International Date Line (180° E/W)

• It is the imaginary zig-zag line passing through the Pacific Ocean from where the date changes.

• Crossing eastbound (Japan to USA), the date is subtracted by 1 day.

• A person gains a day and vice versa.

Concept of Great Circle

• A Great Circle is the largest possible circle that can be drawn around a sphere.

• It divides the Earth into two equal hemispheres.

• All longitudes are Great Circles.

• Equator is the only latitude that is a Great Circle.

Uses of Latitude

Climatology

• Temperature zones

• Wind pressure system

• Planetary wind system

Location of Place

• Hemisphere identification

• Equal division of Earth into two parts

Hemisphere

• Equator divides the globe horizontally into Northern and Southern Hemisphere.

• Prime Meridian divides the globe vertically into Eastern and Western Hemisphere.

SOLSTICE AND EQUINOX

Solstice

• A solstice occurs when the Sun reaches its highest or lowest point in the sky, resulting in the longest or shortest day of the year.

Summer Solstice

• Occurs on 21st June

• Longest day of the year in Northern Hemisphere

• Sun’s vertical rays fall on Tropic of Cancer

• Northern Hemisphere gets more heat

• Continuous sunlight on North Pole for 6 months

Winter Solstice

• Occurs on 22nd December

• Shortest day and longest night in Northern Hemisphere

• Sun’s vertical rays fall on Tropic of Capricorn

• Southern Hemisphere gets more heat

• Continuous sunlight on South Pole for 6 months

Equinox

• Day and night are approximately equal.

• Neither pole is tilted towards the Sun.

• Vernal (Spring) Equinox – 21st March

• Autumnal (Fall) Equinox – 23rd September

ECLIPSES

Solar Eclipse

• Moon comes between Earth and Sun.

• Shadow falls on Earth.

• Occurs during New Moon (Amavasya).

Lunar Eclipse

• Earth comes between Sun and Moon.

• Shadow falls on Moon.

• Occurs during Full Moon (Purnima).

Red Moon

• Earth’s atmosphere scatters blue light and allows red light to reach the Moon.

Blue Moon

• Two Full Moons within a single calendar month.

Types of Solar Eclipse

• Partial Eclipse

• Annular Eclipse

• Total Eclipse

Supermoon

• Occurs when the Moon is closest to Earth during a Full Moon.

• Moon appears larger than normal.

Syzygy

• Alignment of Sun, Moon and Earth in a straight line.

TORRID, TEMPERATE AND FRIGID ZONES

Torrid Zone

• Hottest zone of Earth.

• Receives direct overhead rays of the Sun.

• Located between Tropic of Cancer and Tropic of Capricorn.

Temperate Zone

• Located between Tropic of Cancer and Arctic Circle.

• Located between Tropic of Capricorn and Antarctic Circle.

• Receives slanting rays of the Sun.

Frigid Zone

• Coldest region of Earth.

• Experiences 6 months day and 6 months night.

• Located beyond Arctic Circle (66½° N).

• Located beyond Antarctic Circle (66½° S).

TIDES

Tides

• Periodic rise and fall of ocean water levels.

• Caused by gravitational pull of the Moon and the Sun.

• Two types of tides.

Neap Tides

• Earth, Moon and Sun are in perpendicular alignment.

• Lower tidal range.

Spring Tides

• Earth, Moon and Sun are aligned in a straight line.

• Higher tidal range.