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Chapter 10 Section 2

Rates of Weathering

Objectives

• Explain how the composition of rock affects

the rate of weathering.

• Describe how a rock’s total surface area

affects the rate at which the rock weathers.

• Describe how differences in elevation and

climate affect the rate of weathering.

Ledges exist in nature because

the rock that the ledge is

made of weathers more slowly than the

surrounding rock.

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Differential Weathering“Hard rocks, such as granite, weather more slowly than softerrocks, such as limestone.”

Differential Weathering – softer rocks weather away leaving harder rocks behind.

• Harder rocks = more weather resistant

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The Shape of Rocks

Where does weathering take place?

On the outer surface of rocks

“The more surface area that is exposed to weathering, the faster the rock will be worn down.”

“Smaller rocks have more surface area… and is more exposed to the weathering process.”

Remember the rock weathering lab we did? Which experiment demonstrated how surface area affects the rate of weathering?

(p285)

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Weathering and Climate

Who do you think has fewer worries about the

condition of their car: Someone living in

Georgia or someone living in Arizona? Explain

your answer.

(p286)

Weathering and Climate

Three reasons why weathering happens more in warm humid climates:

1. Oxidation happens faster when temps are warmer

2. Water increases the rate of mechanical weathering

3. Climates of freezing and thawing have more ice wedging

(p286)

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Weathering and Elevation

Rocks of high elevation exposed to more:

• Wind

• Rain

• Ice

(p287)

Weathering and

Elevation

Gravity & weathering

• Steep slopes = quick rainwater run off

• Rainwater carries sediments

• Removing sediment = exposes rock

• Exposed rock = weathering, falling down sides

• Increased surface area = faster weathering

(p287)