Section 12.1WEATHERING

WEATHERING

TWO TYPES:

·Physical Weathering:

·Chemical Weathering:

rocks are broken down without a chemical reaction.

chemical reaction occurs changing the composition of the rock

Ice and water frost wedging – water

seeps into cracks in rock

expands when it freezes causing the crack to expand

Mechanical Weathering

Which type of climate has the greatest amount of rock weathering caused by frost wedging?

1 a dry climate in which temperatures remain below freezing

2 a dry climate in which temperatures alternate from below freezing to above freezing

3 a wet climate in which temperatures remain below freezing

4 a wet climate in which temperatures alternate from below freezing to above freezing

Checkpoint #1

Abrasion Striking rock with

sand, pebbles, and large rocks

Mechanical Weathering

Examples of Abrasion

1. Ice: Glacial

2. Gravity: Mass Movement

3. Water: River, Ocean, Lake action

4. Wind

The picture (see image) shows a geological feature in the Kalahari Desert of southwestern Africa. Which process most likely produced the present appearance of this feature?

1 Wind Erosion

2 Volcanic Eruption

3 Earthquake Vibrations

4 Plate Tectonics

Checkpoint #2

Plants and animals The breakdown of rock

due to plant and animalactivity

Mechanical Weathering

Upward expansion Rock outcrops lift,

exposing them to weathering

Mechanical Weathering

The diagram shows the stump of a tree whose root grew into a small crack in bedrock and split the rock apart.

The action of the root splitting the bedrock is an example of

1 Chemical Weathering

2 Deposition

3 Erosion

4 Mechanical Weathering

Checkpoint #3

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1201/es1201page01.cfm

Mechanical Weathering

Hydrolysis Reaction of water with

other substances

Chemical Weathering

Oxidation oxygen reacts

with rock, breaking them down

produces rust

Chemical Weathering

Think: After thousands of years Cleopatra's Needle looked like the picture on the left. After 100 years in NYC it looks like the picture on the right. Why do you believe this happened?

Pair: Discuss this with someone near you

Share: Be ready to be called on to share your answers

Think-Pair-Share

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1202/es1202page01.cfm

Surface Exposure More surface area more weathering

Composition of rock Some rocks weather better than others

Climate Some climates are more conducive to

weathering

Rates of Weathering