CHAPTER 19 SECTION 4 Weathering and Erosion. Objectives Identify the causes of rock shaping due to weathering and erosion Explain how chemical weathering.

CHAPTER 19SECTION 4

Weathering and Erosion

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

Key Terms

ErosionDepositionAcid rain

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

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

Erosion

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

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)

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)

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

Wind Erosion

Wind can reshape the landscapeWind 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)

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

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