Questions Answers For All Chapters – Geography Class 9th
Exercise
Q1. Tick in front of the correct option ✓
(a) On which of the following are slow movements in the earth’s interior dependent?
- Landforms
- Velocity ✓
- Direction
Answer: Velocity is correct because the chapter says slow movements depend on how fast they happen, like forming mountains over time.
(b) When waves divert from each other, what do they create?
- Compression
- Tension ✓
- Mountain
Answer: Tension is correct because the chapter explains that when waves move away from each other, they pull the rocks apart, creating tension.
(c) For the formation of a rift valley, which of the following processes should occur in the earth’s crust?
- Compression
- Tension ✓
- Weathering
Answer: Tension is correct because rift valleys form when the crust is pulled apart due to waves moving in opposite directions, as per the chapter.
(d) Which of these is a fold mountain?
- The Satpudas
- The Himalayas ✓
- The Western Ghats
Answer: The Himalayas are correct because the chapter lists them as fold mountains formed by pressure folding the earth’s crust.
(e) The formation of extensive plateaus is a result of which type of movements?
- Mountain-building
- Continent-building ✓
- Horizontal
Answer: Continent-building is correct because the chapter says extensive plateaus form when the crust is uplifted by slow continent-building movements.
Q2. Give geographical reasons.
(a) Buildings collapsed at the foothills of the Himalayas because of an earthquake. Before collapsing they were moving forward and backward.
- Earthquakes release energy waves from the earth’s interior, causing the ground to shake.
- The chapter says primary (P) waves move buildings forward and backward, weakening them.
- At the Himalayas’ foothills, this shaking was strong, so buildings collapsed due to the force.
(b) There is a difference in the formation of the Meghalaya Plateau and the Deccan Plateau.
- The Meghalaya Plateau is a block mountain formed by tension pulling the crust apart, creating faults.
- The Deccan Plateau formed from fissure-type volcanic eruptions where lava spread out from cracks.
- The chapter explains these different processes: faulting for Meghalaya and lava flow for Deccan.
(c) Most of the volcanoes are found on the plate boundaries.
- The earth’s crust is made of plates, and boundaries are where plates meet or move apart.
- The chapter says volcanoes form here because magma escapes through weak spots at these edges.
- Fig. 2.18 shows volcanoes concentrated along plate boundaries due to this movement.
(d) The Barren Island is becoming conical in shape.
- Barren Island is an active volcano where magma comes out from a central vent.
- The chapter explains that central-type volcanoes build cone shapes as lava piles up around the vent.
- Repeated eruptions make Barren Island more conical over time.
(e) Volcanic eruptions can cause earthquakes.
- When magma moves up during a volcanic eruption, it creates pressure in the earth’s crust.
- The chapter lists volcanic eruptions as a cause of earthquakes because this pressure can break rocks.
- This sudden movement releases energy, leading to tremors or earthquakes.
Q3. Identify and name the internal movement.
(a) Tsunamis are generated in coastal areas.
- Sudden movement
- This is an earthquake because the chapter says tsunamis happen when ocean earthquakes displace water.
(b) The Himalayas are an example of fold mountains.
- Slow movement
- This is mountain-building (orogenic) movement because the chapter says folds form from pressure over time.
(c) Molten magma is thrown out of the earth’s mantle.
- Sudden movement
- This is a volcanic eruption because the chapter describes it as magma coming out suddenly.
(d) Rift valley is formed because of faulting.
- Slow movement
- This is mountain-building movement because the chapter links faulting to tension forming rift valleys.
Q4. 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 (fault lines) rocks break apart
(e) Stored energy is released in the form of seismic waves
Answer:
- (c) Due to the movements in the mantle, compression goes on increasing
- (b) The plates suddenly move
- (d) Along the weak points (fault lines) rocks break apart
- (e) Stored energy is released in the form of seismic waves
- (a) The earth’s surface vibrates
Explanation: The chapter says tension builds in the mantle first, then plates move, rocks break, energy releases as waves, and the surface shakes.
Q5. Distinguish between –
(a) Block Mountain and Fold Mountain
- Block Mountain: Formed by tension pulling rocks apart, creating faults; has flat tops and steep slopes (e.g., Meghalaya Plateau).
- Fold Mountain: Formed by pressure pushing rocks together, creating folds; has peaks and ridges (e.g., Himalayas).
- The chapter explains block mountains rise between faults, while fold mountains bend under compression.
(b) Primary and Secondary Seismic Waves
- Primary (P) Waves: Fastest, reach first, move forward-backward, travel through solid, liquid, gas (e.g., shake buildings side to side).
- Secondary (S) Waves: Slower, reach after P waves, move up-down, travel only through solids (e.g., more destructive to buildings).
- The chapter says P waves are less harmful, while S waves cause more damage due to their motion.
(c) Earthquakes and Volcanoes
- Earthquakes: Sudden shaking of the ground due to energy release from moving plates or faults; cause cracks, landslides.
- Volcanoes: Eruptions of magma, ash, and gas from the mantle; form mountains or plateaus (e.g., Mt. Fuji).
- The chapter notes earthquakes are tremors, while volcanoes involve material coming out of the earth.
Q6. Answer in brief
(a) Give reasons why an earthquake occurs.
- Earthquakes happen when tension builds up in the earth’s crust due to moving plates.
- The chapter lists causes like plates colliding, sliding, or breaking rocks, releasing energy as waves.
- Volcanic eruptions can also cause earthquakes by disturbing the crust.
(b) Which type of movements have led to the formation of the major fold mountains in the world?
- Slow mountain-building (orogenic) movements form major fold mountains.
- The chapter says pressure from energy waves folds soft rocks over time.
- Examples like the Himalayas show this process happening slowly.
(c) How is the magnitude of the earthquake related to the collapse of houses?
- Magnitude measures earthquake strength on the Richter scale; higher magnitude means more energy.
- The chapter suggests stronger waves (e.g., L waves) from high magnitude can destroy buildings.
- Weak houses collapse more easily when the shaking is intense.
(d) What are the effects of earthquakes on the earth’s surface and human life?
- On the surface: Cracks, landslides, uplifts, subsidence, tsunamis, avalanches (per the chapter).
- On humans: Buildings collapse, causing deaths, injuries, and loss of property.
- Transport and communication also get disrupted, affecting daily life.
(e) Explain the types of seismic waves.
- Primary (P) Waves: Fastest, move forward-backward, travel through all mediums, less destructive.
- Secondary (S) Waves: Slower, move up-down, only through solids, more damaging.
- Surface (L) Waves: Slowest, travel along crust, most destructive (chapter Fig. 2.12).
(f) Explain the types of volcanoes on the basis of periodicity of eruption with examples.
- Active: Erupt regularly now (e.g., Mt. Fujiyama, Japan; Mt. Stromboli, Mediterranean).
- Dormant: Not erupted for long but could erupt (e.g., Mt. Vesuvius, Italy; Barren Island, India).
- Extinct: No eruptions for a long time, unlikely to erupt (e.g., Mt. Kilimanjaro, Tanzania).
Q7. Show the epicentre, focus and the primary, secondary and surface waves of an earthquake with the help of a neat labelled diagram.
Diagram Description (for students to draw):
- Draw the earth’s surface as a horizontal line.
- Below it, mark a point as the focus (where energy starts).
- Directly above on the surface, mark the epicentre (first tremor point).
- Draw wavy arrows from focus to surface labeled P waves (straight, fast).
- Add up-down arrows labeled S waves (slower, wavy).
- Along the surface, draw big wavy lines labeled L waves (most destructive).
Explanation: The chapter (Fig. 2.12) shows focus underground, epicentre above, and waves spreading out.
Q8. Show the following on a given outline map of the world.
(a) Mt. Kilimanjaro: Mark in Tanzania, East Africa (extinct volcano).
(b) Mid-Atlantic Earthquake zone: Draw a line in the Atlantic Ocean between North and South America (plate boundary).
(c) Mt. Fuji: Mark in Japan, near Tokyo (active volcano).
(d) Krakatoa: Mark in Indonesia, between Java and Sumatra (active volcano).
(e) Mt. Vesuvius: Mark in Italy, near Naples (dormant volcano).
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