1. Weathering and Erosion
Chapter 19
Section 4

2. Objectives
Identify the causes of rock shaping due to weathering and erosion
Explain how chemical weathering can form underground caves in limestone
Describe how acid rain affects the landscape

3. Key Terms
Erosion
Deposition
Acid rain

4. Physical Weathering Also called Mechanical Weathering
Breaks rocks into smaller pieces and eventually becomes soil
Ice can break rocks
In a process called frost wedging, water fills in cracks in the rock and splits it apart when it expands during freezing
Plants can break rocks
The roots or other parts of plants can grow into the cracks between rock and split it apart as it grows larger

5. Chemical Weathering
Chemical weathering takes longer and is based on several chemical reactions
Rusting reactions
Iron oxides or rust cause a red color to the land
Think Mars!
Carbon Dioxide
CO2 dissolved in rainwater can “eat away” limestone underground and cause caves to form
Acid Rain
Air pollution can dissolve in rain water and fall to Earth causing rock to “melt” and lakes and rivers to be polluted

6. Erosion
The removal and transportation of weathered and non-weathered materials by:
Running water
Wind
Waves
Ice
Underground water
Gravity

8. Water Erosion
Fast moving water can dissolve and carry away sediments, (small pieces of broken rock material)
When the water slows down, the larger sediments will fall out of the stream of water and become part of the riverbed, (deposited there until the water flow increases)
Huge amounts of sediment encircle our continent, (we see them as beaches)

9. Sea Erosion Sediments can be washed away by ocean waves
Rocks may be put in place to stop this erosion process
Even rocks can be eroded by fast moving water or powerful waves
The type of rock determines how fast erosion occurs, (sandstone faster than igneous rock)

10. Glacier Erosion Ice can move tremendous amounts of rock and soil.
The ice can scrape the landscape and remove everything down to the bedrock
Melt water from glaciers may carry sediments away from the glacier
When the glacier melts away, there may be a different landscape after than what was there before

11. Wind Erosion Wind can reshape the landscape
Wind can carry sediments like water can…
The faster the wind, the heavier the particles
The particles strike objects in their way and can cause erosion at the surface
Sand and other particles, (dust), may be transported and deposited many miles from their source, (like sand dunes on a larger scale)

12. Summary Physical weathering breaks down rock by:
Water erosion, ice wedging, wind abrasion, and glacial abrasion, (there are other forces also0
In chemical weathering, rock is altered by chemical reactions between water and minerals, causing a breakdown of the rock
Carbonic Acid acts as a weathering agent and is responsible for the formation of limestone caves

13. Summary Acid rain can weather rock and harm living organisms.
It is the by-product of fossil fuel emissions, (smog), reacting with water in the atmosphere