Geography Question Answers Chapter 3 Exogenetic Processes Part-1 Class 9 Maharashtra Board

Questions Answers For All Chapters – Geography Class 9th

Exercise

Solutions

Q 1. Answer in brief.

(a) What is mechanical weathering?

• Mechanical weathering is the process where rocks break into smaller pieces without any change in their chemical composition.
• It happens due to physical forces like temperature changes, frost, or pressure release.
• For example, rocks crack when they expand and contract due to heat or when water freezes in their crevices.

(b) What are the main types of chemical weathering?

• The main types of chemical weathering are carbonation, solution, and oxidation.
• Carbonation occurs when rainwater mixes with carbon dioxide to form carbonic acid, dissolving rocks like limestone.
• Solution happens when minerals in rocks dissolve in water, making them brittle.
• Oxidation is when iron in rocks reacts with water and oxygen, forming rust.

(c) How does biological weathering occur?

• Biological weathering occurs when living organisms break down rocks.
• Plant roots grow into cracks, expand, and split rocks apart.
• Burrowing animals like ants, rats, or rabbits dig into the ground, loosening rocks.
• Algae, moss, and lichens grow on rocks and help break them down over time.

(d) Distinguish between weathering and mass wasting.

• Weathering is the breaking down of rocks into smaller pieces by external processes like temperature, water, or organisms.
• Mass wasting is the movement of weathered rock materials down slopes due to gravity.
• Weathering happens in place, while mass wasting involves the shifting of materials.
• For example, exfoliation is weathering, but a landslide is mass wasting.

Q 2. Write whether the statements are true or false. Correct the incorrect ones.

(a) Climate affects earthquakes.

• False.
• Corrected: Climate does not affect earthquakes; earthquakes are caused by internal earth movements, not climate.

(b) Mechanical weathering is less effective in humid climates.

• True.
• In humid climates, chemical weathering is more effective due to more water, while mechanical weathering is less dominant.

(c) Mechanical weathering happens on a large scale in dry climates.

• True.
• In dry climates, temperature changes and lack of moisture make mechanical weathering more common.

(d) The breaking down of rocks into smaller particles is called weathering.

• True.
• Weathering is the process of breaking rocks into smaller pieces by external forces.

(e) Lateritic rocks are formed through exfoliation.

• False.
• Corrected: Lateritic rocks are formed through chemical weathering, not exfoliation, which is a mechanical process.

Q 3. Complete the flowchart below.

Weathering Process

1. Physical Weathering

   • Exfoliation

   • Frost action

2. Chemical Weathering

   • Solution

   • Oxidation

   • Carbonation

3. Biological Weathering

   • Burrowing by animals

   • Root action

Q 4. Identify the type of weathering from the given description.

(a) Some animals live inside the grounds by making burrows.

• Biological weathering.
• Burrowing animals break rocks by digging into them.

(b) The rock rusts.

• Chemical weathering (Oxidation).
• Rusting happens when iron in rocks reacts with water and oxygen.

(c) Water which has accumulated in the crevices of the rocks freezes. Consequently, the rock breaks.

• Mechanical weathering (Frost).
• Freezing water expands in cracks, breaking the rock.

(d) The pipes supplying water in colder regions break.

• Mechanical weathering (Frost).
• Water freezes and expands in pipes, causing them to break, similar to rocks.

(e) Sand formation occurs in deserts.

• Mechanical weathering (Granular weathering).
• Rocks break into sand particles due to wind and temperature changes in deserts.

Q 5. Using internet, look for incidences of a few landslides that have occurred in India and write about them briefly.

Malin Landslide (2014):

• Occurred on July 30, 2014, in Malin village, Pune district, Maharashtra.
• Heavy rainfall triggered a mudslide, burying over 40 houses and killing 151 people.
• The steep slope and weathered soil contributed to this rapid mass movement.

Kedarnath Landslide (2013):

• Happened in June 2013 in Uttarakhand during heavy floods.
• Landslides and flash floods destroyed homes, roads, and temples, killing over 5,000 people.
• Excessive rain and unstable slopes caused the disaster.

Kerala Landslides (2018):

• Took place in August 2018 in Idukki and Wayanad districts during monsoon floods.
• Heavy rain led to landslides, killing over 400 people and displacing thousands.
• Weathered slopes and deforestation worsened the event.