Published by Pearson Education India Authored by Edgar Thorpe & Showick Thorpe

Published by Pearson Education IndiaAuthored byEdgar Thorpe & Showick ThorpePART 1: Basic Knowledge About The Earth [Section 3]

Topics Covered Slide Numbers3.1 Shape [2 ]3.2 Structure [3]3.3 Composition [4]3.4 Geological history [5]3.5 Earth’s movements [6-8]3.6 Seasons [9]3.7 Equinoxes and Solstices [10]3.8 Eclipses [11]

Question 1: What is the shape of the Earth’s orbit around the Sun? Is it elliptical or oblate spheroid?

Answer: Oblate spheroid.

Extra Fact Punch:

Oblate spheroid means flattened at the poles with a slight bulge at the equator.

Question 2: Which layer is responsible for Earth’s magnetism?

Answer: The Earth’s inner core.

Extra Fact PunchThe Earth’s inner core solid and of depth of 1,370km. It contains Nickel and Iron that create the magnetic effects.

Question 3: Of the 8 important elements constituting the Earth surface. Which element is the most abundant?

Answer: Oxygen(46.5%). Extra Fact Punch

The earth is made up of more than 100 elements.

Question 4: Geological history of the present living world can be best tracked by four Era’s in the sequence of____.

Answer: (a) Pre-cambium Era. (b) Paleozoic era. (c) Mesozoic Era. (d) Cenozoic Era. Extra Fact PunchThe pre-cambium era originated 4,600 million years ago and ends 570 million years ago. And then starts the Paleozoic era, and lasts till 225 million years. then the Mesozoic era started about 251 million years ago and ended 65 million years ago and the last Era started about million years ago.

Question 4:Rotation and revolution relate to earth’s movement. The earth spins on its imaginary axis from west to east once in 24 hour. It is also known as_____.

Answer: Diurnal or daily motion.

Extra Fact PunchThe imaginary axis always remain inclined at an angle 66.5 degrees to the plane of the Earth’s orbit.

Question 5: If June 22 and December 21 are shortest night and longest night in northern hemisphere respectively. Then date the shortest and longest night in the southern hemisphere. Answer: December 22 shortest night June 21 longest night.

Extra Fact PunchDays and night are equal at equator throughout the year, as the circle of illumination always divide the equator in two equal parts.

Question 9: State the duration of one revolution of Earth around the sun?

Answer:365 days, 6 hours, 9 minutes, and 9.54 seconds.

Extra Fact PunchThe journey of the Earth around the Sun is called revolution. It takes one solar year to complete the journey..

Question 6: What are the two factors responsible for causing change in season?

Answer: (a) Revolution of the Earth around the Sun. (b) A fixed inclination of the Earth’s axis at 66.5 degrees to the plane of its orbit.

Extra Fact PunchThe first half of the year the northern hemisphere tilts towards the sun resulting in longer days and the summer season in the region and the southern hemisphere experiences winter.

Question 7: March 21 is called vernal equinoxes then September 23 is known as______.

Answer: Autumnal equinox.

Extra Fact PunchEquinoxes are the dates when the days and nights are equal.

Question 8: What is the mechanism behind solar and lunar eclipse?

Answer: When the light of the Sun or the moon is masked by another body the Sun or Moon is said to be in eclipse.

Extra Fact PunchLunar eclipse occurs only on full moon day and solar eclipse occurs on a new moon day, when the moon is inline with the Sun.