prentice hall earth science ch05 weathering & erosion
TRANSCRIPT
Chapter
55 Erosion and weathering are major forces
that shape Earth’s surface.
For example, the Grand Canyon was formed through erosion by the Colorado River running through it!
Weathering, Soil, and Mass Movements
Mechanical Weathering
5.1 Weathering
Mechanical weathering occurs when physical forces break rock into smaller and smaller pieces without changing the rock’s mineral composition.
In nature three physical process are especially important causes of weathering: frost wedging, unloading, and biological activity.
What is weathering?
Weathering: The breaking down of rocks into smaller pieces.
1. Mechanical /Physical
2. Chemical
5 Agents of Mechanical Weathering:
1. Release of Pressure
2. Freezing & Thawing
3. Animal Actions
4. Plant Growth
5. Abrasion
Mechanical Weathering
5.1 Weathering
• Reduced pressure on igneous rock causes it to expand and allows slabs of outer rock to break off in layers in a process called exfoliation.
1. Release of Pressure
Mechanical Weathering
5.1 Weathering
2. Frost wedging
• The mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices
Freezing & ThawingWhen water in the cracks
of rocks freezes it expands causing the crack to enlarge or get bigger. The ice melts & refreezes over & over, breaking the rock apart.
Mechanical Weathering
5.1 Weathering
3. Biological activity
• The activity of organisms, including plants, burrowing animals, and humans, can also cause mechanical weathering.
Mechanical Weathering
5.1 Weathering
3. Biological - Plant growth
• Plants roots can grow into cracks in the rock, slowly breaking them apart.
Plant Root Growth
Mechanical Weathering
5.1 Weathering
4. Biological – Animal actions
Animals dig (burrow) through the ground to make their homes. This loosens the soil & breaks apart rocks.
5.1 Weathering
5. Abrasion
Sand and other rock particles in wind, water or ice can wear away exposed rock surfaces.
Like sandblasting or sandpaper on wood
Sand-Blasting
Chemical Weathering
5.1 Weathering
Chemical weathering is the breaking down of rock through chemical reactions.
Chemical Weathering
5.1 Weathering
5 Agents of Chemical Weathering1. Water2. Oxygen3. Carbon Dioxide4. Living Organisms5. Acid Rain
Chemical Weathering
5.1 Weathering
5 Agents of Chemical Weathering1. Water – Water dissolves rock.2. Oxygen – Chemically changes rock
through a process called Oxidation.
Oxygen + Water + Iron = RustOxygen + Water + Iron = Rust
Chemical Weathering
5.1 Weathering
5 Agents of Chemical Weathering1. Water – Water dissolves rock.2. Oxygen – Chemically changes rock
through a process called Oxidation.3. Carbon Dioxide – forms carbonic acid.
Chemical Weathering
5.1 Weathering
CO2 + rainwater = Carbonic Acid
Carbonic Acid weathers softer rock like limestone & marble as it seeps into spaces in rock.
Examples: Karst topography – caves, sinkholes
Chemical Weathering
5.1 Weathering
5 Agents of Chemical Weathering1. Water – Water dissolves rock.2. Oxygen – Chemically changes rock
through a process called Oxidation.3. Carbon Dioxide – forms carbonic acid.4. Living Organisms -
The roots of plants make a weak acid that slowly dissolves rocks around the plant.
Chemical Weathering
5.1 Weathering
5 Agents of Chemical Weathering1. Water – Water dissolves rock.2. Oxygen – Chemically changes rock
through a process called Oxidation.3. Carbon Dioxide – forms carbonic acid.4. Living Organisms -
Chemical Weathering
5.1 Weathering
5 Agents of Chemical Weathering1. Water – Water dissolves rock.2. Oxygen – Chemically changes rock
through a process called Oxidation.3. Carbon Dioxide – forms carbonic acid.4. Living Organisms - Lichen, mosses5. Acid Rain – rapid weathering
• http://classroom.synonym.com/effects-acid-rain-cemetery-stones-19291.html
• http://www.dnrec.state.de.us/DNREC2000/Divisions/AWM/aqm/education/airqualityLesson6.pdf
• Summary & Quiz