8-1 rocks and weathering 1)how do rocks and weathering affect earth’s surface? 2)what are the...

8-1 Rocks and Weathering

1) How do rocks and weathering affect Earth’s surface?

2) What are the causes of mechanical weathering ands chemical weathering?

3) What determines how fast weathering occurs?

How do arches form?

Define: “Weathering”

• “Weathering” is the process that breaks down rock on Earth’s Surface.

Erosion• “Erosion” is

the removal of rock particles by wind, water, or gravity.

Uniformitarianism “Uniformitarianism”

is the principle that the processes that operate today are the same processes that operated in the past.

Mechanical Weathering

• The type of weathering that breaks rocks into smaller pieces.

Chemical Weathering

• “Chemical Weathering” is the type of weathering that breaks down rock through chemical changes.

Types of Mechanical Weathering

• Release of Pressure

• Freezing and Thawing

• Animal Actions• Plant Growth• Abrasion

Release of Pressure

• Erosion removes material from the surface of a mass of rock, this reduces pressure on the rock and causes it to crack.

Freezing and Thawing

When water freezes in cracks in a rock it expands and makes the crack bigger, this is called “Ice Wedging”

Animal Actions

• Animals that burrow break up rock and soil.

• Their burrowing also exposes more rock to weathering.

Plant Growth

• The roots of trees and other plants enter cracks in rock. As the plant grows its roots force the crack to widen.

Abrasion• Sand or rock

particles carried by wind or water wear away at rock.

• This is similar to sandpaper being used on wood.

Chemical Weathering

• The types of chemical weathering include the action of water, oxygen, carbon dioxide, living organisms and acid rain.

Living Organisms

• Plant roots can produce weak acids that wear away rock.

• Lichens for example.

Acid Rain

• Compounds from fossil fuels can mix with water in the atmosphere and come down as acid rain.

• This causes rapid chemical weathering.

Action of Water

• Most important cause of chemical weathering

• Water dissolves rock making a solution.

Oxygen

• Oxygen combined with water will cause iron to undergo Oxidation otherwise known as rust.

Carbon Dioxide• Carbon dioxide can

dissolve into rainwater and create a weak acid called Carbonic acid.

• This weak acid easily weathers marble and limestone.

Rate of Weathering

• Type of Rock and the climate affect the rate of weathering.

• Some rocks are more permeable and weather faster.

• Chemical weathering occurs more quickly in warm climates.