Q 1. Tick in front of the correct option ✓
(a) On which of the following are slow movements in the earth’s interior dependent?
(1) Landforms
(2) Velocity
(3) Direction
Ans.
Landforms
Velocity ✔
Direction
(b) When waves divert from each other, what do they create.
(1) Compression
(2) Tension
(3) Mountain
Ans.
(1) Compression
(2) Tension ✔
(3) Mountain
(c) For the formation of a rift valley, which of the following processes should occur in the earth’s crust?
(1) Compression
(2) Tension
(3) Weathering
Ans.
(1) Compression
(2) Tension ✔
(3) Weathering
(d) Which of these is a fold mountain?
(1) The Satpudas
(2) The Himalayas
(3) The Western Ghats
Ans.
(1) The Satpudas
(2) The Himalayas ✔
(3) The Western Ghats
(e) The formation of extensive plateaus is a result of which type of movements ?
(1) Mountain-building
(2) Continent-building
(3) Horizontal
Ans.
(1) Mountain-building
(2) Continent-building ✔
(3) Horizontal
Q 2. Give geographical easons.
(a) Buildings collapsed at the foothills of the Himalayas because of an earthquake. Before collapsing they were moving forward and backward.
Ans. (1) The seismic primary or ‘P’ waves are the first ones to reach the surface of the earth after the energy is emitted in the earth’s interior. (2) They travel at a very fast speed from the focus of the earthquake in radial direction. (3) Subjected to a P wave, particles in the rock move in the direction of waves to and fro (forward-backward). (4) Therefore before collapsing the buildings at the foothills of the Himalayas they were moving forward and backward.
(b) There is a difference in the formation of the Meghalaya Plateau and the Deccan Plateau.
Ans. (1) The Meghalaya plateau is formed due to slow movements (orogenic movements) whereas the Deccan Plateau is formed due to sudden movements (fissure volcano). (2) During the formation of the Meghalaya plateau, a part of the Earth’s crust in between two parallel faults was lifted forming a plateau whereas, the Deccan plateau was formed due to molten material coming out with the eruption spreading on both sides of the fissure. (3) Thus, there is a difference in the formation of the Meghalaya plateau and the Deccan plateau.
(c) Most of the volcanoes are found on the plate boundaries.
Ans. (1) Plate boundaries are directly related to areas of earthquakes and volcanoes. (2) The part of the plate boundary which slides under the crust, results in the loss of material. Such boundaries are called plate consuming boundaries. (3) In areas where new material (magma) is coming up onto the Earth’s crust, they are called plate creating boundaries. Both the processes result in earthquakes and volcanoes. Thus, most of the volcanoes are formed in the plate boundaries.
(d) The Barren Island is becoming conical in shape.
Ans. (1) Barren volcano was dormant for a long time. But, in February 2017, it started erupting. (2) Mainly dust, smoke and mud is coming out of this eruption along with some lava. (3) As a result, a cone-shaped mountain starts forming. Therefore Barren Island is becoming conical in shape.
(e) Volcanic eruptions can cause earthquakes.
Ans. (1) Sometime volcanic eruptions can cause earthquakes because due to the tension in the interior of the earth, fractures in rock layer is formed leading to the formation of magma. (2) The magma rises upward along the gap between the two plates leading eruption of volcanoes. (3) Due to tremendous pressure at the time of volcanic eruption, the earth’s surface trembles leading to earthquake.
Q 3. Identifyand name the internal movement.
(a) Tsunamis are generated in coastal areas.
Ans. Sudden Movements.
(b) The Himalayas are an example of fold mountains.
Ans. Orogenic movement / Slow movement.
(c) Molten magma is thrown out of the earth’s mantle.
Ans. Sudden Movements.
(d) Rift valley is formed because of faulting.
Ans. Orogenic movement / Slow movement.
Q 4. Arrange the following statements in chronological order in which an earthquake occurs.
(a) The earth’s surface vibrates
(b) The plates suddenly move.
(c) Due to the movements in the mantle, compression goes on increasing.
(d) Along the weak points ( faultlines) rocks break apart.
(e) Stored energy is released in the form of seismic waves.
Ans.
(a) The plates suddenly move.
(b) Due to the movements in the mantle compression goes on increasing.
(c) Along the weak point (faultlines) rocks break apart.
(d) Stored energy is released in the form of seismic waves.
(e) The earth’s surface vibrates.
Q 5. Distinguish between –
(a) Block Mountain and Fold Mountain
Ans. 
(b) Primary and Secondary Seismic Waves
Ans. 
(c) Earthquakes and volcanoes
Ans. 
Q 6. Answer in brief
(a) Give reasons why an earthquake occurs.
Ans.
(1) Earthquake occurs due to the energy released by increased tension in the earth’s crust by the movements occurring in its interior.
(2) Some of the major causes of earthquake are as follows;
(a) Moving of the plates in the earth’s interior
(b) Colliding of plates
(c) Plates sliding below the other
(d) Forming of fractures in rock layers due to tension in the interior of the earth.
(e) Occurring of volcanic eruptions
(b) Which type of movements have led to the formation of the major fold mountains in the world?
Ans.
(1) Fold mountains are formed due to mountain building (orogenic) movements. (2) Energy is transferred from the interior of the earth. Because of these energy waves and pressure working towards each other and in horizontal direction, the layers of the soft rocks form folds. (3) If the pressure is very high, large scale folds are formed and their complexity increases. (4) As a result, the surface of the earth gets uplifted and fold mountains are formed.
(c) How is the magnitude of the earthquake related to the collapse of houses
Ans.
(1) The magnitude of the earthquake will determine the intensity of the seismic waves generated from the focus of the earthquake. (2) The primary waves cause forward-backward movement of the buildings and other structures on the earth’s surface. This does not cause a lot of destruction. (3) The secondary waves reach earth’s surface after primary waves and the surface waves are generated after both the primary and secondary waves. Both of these waves are more destructive than the primary waves. (4) The increase in the magnitude of the earthquake will result in the above three waves to cause more destruction. Thus, the magnitude of the earthquake is related to the collapse of houses.
(d) What are the effects of earthquakes on the earth’s surface and human life?
Ans.
Following are the effects of earthquakes:
(l) Cracks/fractures develop on the ground. (2) These causes landslides which leads to sliding of rocks. (3) Sometimes the groundwater changes its course. For example, wells may get water, or may dry up. (4) Some areas get uplifted while some may subside. (5) Tsunamis are generated in oceans. These waves can cause great loss of life and property in the coastal areas. (6) In snow-covered areas, avalanches may occur. (7) Buildings collapse and loss of life and property occurs. (8) Transportation routes gets disrupted. (9) Communication system collapses.
(e) Explain the types of seismic waves.
Ans.
The seismic waves can be divided into primary, secondary and surface waves.
(i) Primary or ‘P’ waves : These are the first ones to reach the surface of the earth after the energy is emitted in the earth’s interior. They travel at a very fast speed from the focus of the earthquake in radial direction. The wave moves to and fro, therefore these waves are also called forward-backward waves. These waves can travel through all the three states – liquid, solid and gaseous. It is because of the primary waves that the buildings on the earth’s surface move back and forth.
(2) Secondary or ‘S’ waves : The waves which reach the earth’s surface after the primary waves are called secondary waves. These waves also scatter in all directions from the focus of the earthquake. Their velocity is lesser than the P waves. The particles lying in the way of these waves move up and down in the direction of energy transfer. These waves can travel only through the solid medium. The buildings on the earth’s surface move up and down because of these waves.
(3) Surface or ‘L’ waves : These waves are generated after the main P and S waves reach the epicenter. They travel in the direction of the circumference of the earth along the crust. They are highly destructive.
(f) Explain the types of volcanoes on the basis of periodicity of eruption with examples.
Ans.
According to the periodicity of the volcanic eruptions, three types of volcanoes can be identified.
(1) Active Volcanoes –
(a) If the volcanic eruptions are regular even in the present times, then such volcanoes are called active volcanoes.
(b) E.g., Mt Fujiyama in Japan and Mt. Stromboli in Mediterranean Sea.
(2) Dormant Volcanoes –
(a) When a volcano has not erupted since long, but may become active suddenly is called dormant volcano.
(b) E.g., Mt. Vesuvius in Italy, Mt. Katmai in Alaska and Barren Island, India.
(3) Extinct volcanoes –
(a) Those volcanoes which have not erupted in the past since long and are not likely to erupt in the future are called extinct volcanoes.
Q 7. Show the epicentre, focus and the primary, secondary and surface waves of an earthquake with the help of a neat labelled diagram.
Ans.
Q 8. Show the following on a given outline map of the world.
(a) Mt. Kilimanjaro
(b) Mid-Atlantic Earthquake zone
(c) Mt. Fuji
(d) Krakatoa
(e) Mt. Vesuvius
Ans. 