GEOGRAPHY TOPICAL QUESTIONS AND ANSWERS

What is mechanical weathering?

1/3/2021

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KCSE Geography Paper 1 2001 Section A Question 3.

(a) What is mechanical weathering?

It is the breaking down/ disintegration of rocks into smaller particles without altering the minerals composition of the rock/ breaking down or rocks by physical force

(b) How is an exfoliation dome formed?

A large homogeneous rock is exposed to alternate expansion and contraction of the outer layer in a rock. This is caused by temperature differences. Once the material has peeled off and rolled away a smooth dome shaped rock is left behind. It is called an exfoliation dome.

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State two conditions which may influence the occurrence of landslides

24/2/2021

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KCSE Geography Paper 1 2003 Section A Question 3.

a) State two conditions which may influence the occurrence of landslides

Nature of materials
Extent of saturation /amount of rainfall
The angle of slope/gradient of the land
Human activities/ mining /building
Occurrence of earthquakes/volcanic eruptions

b) Using the diagram (in question paper), name

(i) The type of mass movement shown

Rock fall

(ii) The features marked P and Q

P- cliff face/steep slope
Q-Talus/ talus creep/scree

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Give two processes involved in each of the following types of weathering

19/2/2021

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KCSE Geography Paper 1 2006 Section A Question 2.

Give two processes involved in each of the following types of weathering
(a) Physical weathering

Pressure release/ offloading/ sheeting
Block disintegration
Exfoliation
Frost action/ frost shattering
Crystal growth/ crystallization
Slaking/ wetting and drying
Granular disintegration

(b) Chemical weathering

Hydrolysis
Solution
Oxidation
Carbonation
Hydration

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What is the difference between weathering and mass wasting?

18/2/2021

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KCSE Geography Paper 1 2007 Section B Question 10.

(a) (i) What is the difference between weathering and mass wasting?

Weathering – is the breaking down and decomposition of solid rocks on the earth though physical and chemical processes without movement.
Mass wasting- down slope movement of the weathered material by the aid of gravity.

(ii) Apart from plants, give three other factors that influence the rate of weathering

Water
Heat/ temperature
Chemicals/ dissolved substances

(a) (i) What is the difference between weathering and mass wasting? (ii) Apart from plants, give three other factors that influence the rate of weathering (iii) Explain two ways in which plants cause weathering (b) (i) List two types of mass wasting other than soil creep (ii) Explain three factors that cause soil creep. (c) Explain four effects of mass wasting on the environment.

(iii) Explain two ways in which plants cause weathering

Plants roots e.g. trees grows into joints and cracks, they widen the joints and cracks as they grow causing rock blocks to disintegrated.
Plants like algae, mosses and lichen retain water on rocks resulting to chemical weathering processes
Decaying plant material produce organic acids. That reacts with some of the rock minerals causing it to decay.

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What is weathering?

9/2/2021

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KCSE Geography Paper 1 2011 Section A Question 2.

(a) What is weathering?

Weathering is the breaking down/disintegration and decomposition of rocks at or near the earth's surface in situ by physical or chemical process.

(b) Give three factors that influence the rate of weathering.

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Explain the following processes of weathering:

7/2/2021

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KCSE Geography Paper 1 2012 Section B Question 8.

(a) Explain the following processes of weathering:
(i) hydration;
(ii) oxidation;
(iii) frost action.

(i) Hydration: In hydration certain rock minerals absorb water and expand.
This causes internal stress in the rock and it eventually disintegrates.
(ii) Oxidation: Oxidation takes place in rocks that contain iron.
The iron combines with oxygen forming iron oxides/Ferric oxide
Such rocks change colour and crumble easily.
(iii) Frost action
In temperate/high mountain areas, water may occupy services/cracks in the rocks during the day.
At night the temperatures drop below freezing point causing the water to freeze/expand, exerting pressure in the cracks.
During the day, temperatures rise, causing the ice to melt thus releasing pressure in the cracks.
This alternate freeze-thaw action weakens the rock causing it to disintegrate.

(b) Describe how an exfoliation dome is formed.

In arid/semi arid areas, there is large diurnal ranges of temperature.
During the day, a homogenous rock is intensely heated/at night, the rock looses heat rapidly.
The differential heating causes the outer layer to expand/contract faster than the inner layer.
When this expansion and contraction takes place repeatedly, stress develops in the outer layer of rocks. Cracks appear on the surface layer.
Eventually, the outer layer peels off.
The peeling off leaves behind a rounded mass of rock known as exfoliation dome.

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Apart form alternate wetting and drying, name three other processes of mechanical weathering.

1/2/2021

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KCSE Geography Paper 1 2015 Section B Question 9.

(a) (i) Apart form alternate wetting and drying, name three other processes of mechanical weathering.

Exfoliation/onion peeling/spalling
Block disintegration/block separation
Pressure release
Granular disintegration
Frost action
Crystal growth

(ii) Describe the following processes of weathering:
alternate wetting and drying;
hydrolysis:
carbonation.

Alternate wetting and drying

During the wet season surface rocks such as clay/shale absorb water causing them to swell.
During the dry season these rocks dry out causing the outer surface to shrink.
Repeated wetting and drying weakens the rocks leading to cracking/slaking.
These rocks break away from the main rock.

Hydrolysis

This is a process in which hydrogen ions/hydroxyl ions in water react with mineral ions in a rock.
This reaction leads to formation of new chemical compounds in the rocks.
With alteration of the original minerals, the rock becomes weak and disintegrates/decays.

Carbonation

It involves rain water dissolving carbon 4 oxide in the atmosphere forming a weak carbonic acid.
The carbonic acid reacts with calcium carbonate in rocks to form calcium bicarbonate solution.
Calcium bicarbonate solution is removed by running water.
This leads to the weakening/disintegration of the rock.

(b) (i) State three conditions that influence the process of solifluction in mass wasting.

The presence of a gentle slope.
The occurrence of alternating warm and cold season.
Presence of a permafrost layer/frozen ground/bedrock.
Unconsolidated saturated weathered materials/debris.

(ii) Give three negative effects of mass wasting on the physical environment.

Destruction of vegetation.
Blockage of rivers/disruption of flow of rivers.
Exposure of land to agents of soil erosion.
Loss of life/property.
Results in the formation of scars on the land/derelict land.

(i) Apart form alternate wetting and drying, name three other processes of mechanical weathering. (ii) Describe the following processes of weathering: alternate wetting and drying; hydrolysis: carbonation

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Name two types of landslides.

27/1/2021

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KCSE Geography Paper 1 2018 Section B Question 9.

(a) Name two types of landslides.

Slump
Debris slide
Rock slide
Debris fall
Avalanche
Rock fall.

(b) Explain how each of the following factors influence mass wasting:
(i) Climate
(ii) Slope

Climate

(i)- Areas that receive high rainfall experience massive landslides on steep slopes areas that receive low rainfall have slow movement of rock materials down the slope.
- In areas with large diurnal range of temperature there is expansion and contraction of soil particles which leads to movement of the soil particles.
Alternate freezing and thawing encourage mass movement of rock and soil materials.

(ii) Slope

-Steep slopes encourage faster movement of material down the/ Gentle slopes have slow movement of materials down the

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List Five process involved in chemical weathering and ways in which soil creep occurs

26/1/2021

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KCSE Geography Paper 1 1998 Section B Question 7.

(a) (i) What is the difference between weathering and mass wasting

Weathering is the break down/ disintegration and decomposition of rocks in site while weathered materials under the influence of gravity
(Weathering 2 mks)
(Mass wasting 2 mks)

(ii) List Five process involved in chemical weathering

Solution
Oxidation
Hydration
Carbonation
Hydrolysis

(b) Explain five ways in which soil creep occurs

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