WeatheringWeathering Students will be able to

describe and give examples of chemical

and physical weathering.

Weathering• The breakdown of materials on Earth’s

crust into smaller pieces.

Two Types of WeatheringVenn Diagram

• Mechanical Weathering

• Chemical Weathering

Mechanical Weathering• Process by which rocks are broken down

into smaller pieces by external conditions.• Types of Mechanical Weathering

– Frost Action• Ice Wedging

– Wind– Water– Abrasion– Plant growth– Animals

Ice wedging: water is confined in cracks or pores then freezing on the rock surface and

downward into the rock, solidifying and expanding deeper inside, thus wedging the

rocks apart.

Ice Wedging

Ice wedging slowly breaks up this sedimentary rock into

unusual shapes.

Abrasion• Water

• Moves rocks, making them hit each other

• Wind• Blows sand against rocks

• Gravity• Rocks rub against each other as

they slide downhill

These rocks have been blasted by wind and sand causing them to

become rounded.WIND

Water• Rivers, streams, and runoff

This is a picture of the Half

Dome. The rock is peeling away

from the mountain in

layers just like an onion. This is exfoliation.

(Abrasion)

Plant Growth

Plant growth

The tree is growing in the

rock and soon the rock will break

apart because of the tree roots.

Animals

Chemical Weathering

• The process that breaks down rock through chemical changes. Greatest in warm/wet environments.

• The agents of chemical weathering– Water– Acid in ground water– Living organisms– Acid Precipitation (rain, snow)– Oxygen

Water

• Water weathers rock by dissolving it

Acids in Groundwater: Caves and caverns typically form in limestone

stalactites - hang from ceiling stalagmites - on the ground

The lichen covered boulder produces a habitat for mosses and eventually higher

plants which continue the breakdown of the rock surface by producing weak acids.

Acid Precipitation

1908 to 1969

Acid precipitation has eaten away this limestone statue. Rain, sleet, ice snow, that contains a high concentration of

acids.

Oxygen the second most common element in the air we

breathe, reacts with iron in minerals to form iron oxide minerals, e.g. hematite (rust). As many minerals

contain iron, it is not unusual to see red-colored rocks like the example from Arches National Park shown

here.

Weathering and Erosion Video1. What is an example of weathering and erosion in the restroom?2. Weathering means _________________. Erosion means

____________________.3. What 3 ways does water cause weathering?

1.2.3.

4. What are the 2 types of weathering?1.2.

5. What are the 2 types of erosion?1.2.

https://youtu.be/exS9gFXgib0

Karst Topography• A type of landscape in rainy regions where

there is limestone near the surface, characterized by caves, sinkholes, and disappearing streams.

• Created by chemical weathering of limestone

Karst Topography Video1. What are karst topography examples?2. Why is pollution of karst land forms harmful to the

environment?3. Where are there a lot of karst environments?4. How does pollution affect cave systems outside of urban

environments?5. What university is the leader in karst topography

research?6. Where can you find materials on karst topography

online?

https://www.youtube.com/watch?v=DBUZLNIlAmg

Features of Karst: Sinkholes

Features of Karst: Caves

Features of Karst: Disappearing Streams