WeatheringWeathering is the break- is the break-up of rock due to up of rock due to exposure to the exposure to the

atmosphere.atmosphere.

WeatheringWeathering involves two involves two processes that often processes that often

work together to work together to decompose or break decompose or break

down rocks.down rocks.

Chemical and MechanicalChemical and MechanicalWeathering!Weathering!

Chemical weatheringChemical weathering, or , or decomposition, takes place decomposition, takes place when at least some of the when at least some of the

rock’s minerals are changed rock’s minerals are changed into different substances.into different substances.

Chemical processes include Chemical processes include rain, acid etching by plants, rain, acid etching by plants,

oxidizing, and demineralizing oxidizing, and demineralizing by water.by water.

Chemical

Weathering

Mechanical weatheringMechanical weathering, or , or disintegration, involves physically disintegration, involves physically

breaking rocks into fragments breaking rocks into fragments without changing the chemical without changing the chemical make-up of the minerals within make-up of the minerals within

them.them.

There are four main sources of power There are four main sources of power for mechanical weathering.for mechanical weathering.

Gravity, Water, Wind, & WavesGravity, Water, Wind, & Waves

Of these, water appears to be the Of these, water appears to be the leader in changing the surface.leader in changing the surface.

If a particle is loosened by weathering, but stays put, its

just weathering. If it starts moving, its Erosion.

Remember this!: You’ll be quizzed soon!

Mechanical weathering Mechanical weathering processes, many of which processes, many of which

are erosional, include are erosional, include some of the following.some of the following.

Frost WedgingFrost Wedging

Frost WedgingFrost Wedging is the freezing is the freezing and thawing of and thawing of

water in water in cracks.cracks.

Mechanical ExfoliationMechanical Exfoliation

Mechanical Mechanical Exfoliation Exfoliation is the is the

peeling off of peeling off of sheets of rock as sheets of rock as they expand and they expand and

crack.crack.

Crystal Growth WedgingCrystal Growth Wedging

Crystal Growth Crystal Growth WedgingWedging

involves salt involves salt crystals growing crystals growing

from salty from salty waters.waters.

Crystal Growth WedgingCrystal Growth Wedging

Crystal Growth Crystal Growth WedgingWedging usually usually

occurs near occurs near coastlines as it coastlines as it

has on this has on this granite.granite.

Root PenetrationRoot Penetration

Plant roots have to be strong to Plant roots have to be strong to survive the elements.survive the elements.

Root PenetrationRoot Penetration

Powerful plant Powerful plant roots grow into roots grow into rock cracks and rock cracks and cause fractures.cause fractures.

AbrasionAbrasion

Both wind and Both wind and water can water can

cause cause abrasion abrasion as rock as rock

fragments fragments bounce off bounce off each other.each other.

AbrasionAbrasion

This “moon This “moon looking” picture looking” picture of an Antarctic of an Antarctic

rock, shows rock, shows weathering weathering

from the wind from the wind blown sands.blown sands.

Glacial WeatheringGlacial Weathering

Glaciers and avalanches can Glaciers and avalanches can cause weathering as ice and cause weathering as ice and

rock interact.rock interact.

Other Agents of WeatheringOther Agents of Weathering

Things likeThings like flash flash floods, mud floods, mud

slides, slides, landslides, and landslides, and other forms of other forms of mass wasting mass wasting

can cause can cause weathering. weathering.

ErosionErosion

Remember: Remember: Erosion involves Erosion involves removalremoval and and transporttransport..

ErosionErosionRainRain,, wind wind, and , and streamsstreams are all are all

agents of erosion.agents of erosion.

Can you think of any others? Can you think of any others?

Get out a piece of paper and Get out a piece of paper and identify if the following identify if the following

involve involve weathering, erosion, weathering, erosion, both, or neither.both, or neither.

Ready?Ready?

1.Waves are crashing on a sand 1.Waves are crashing on a sand beach.beach.

2.Water expands as it freezes in 2.Water expands as it freezes in the cracks of rocks.the cracks of rocks.

3. Pebbles move down a stream 3. Pebbles move down a stream with the current.with the current.

4. Acid rain causes the 4. Acid rain causes the decomposition of a statue in New decomposition of a statue in New York.York.

5. A man shovels dirt to plant a tree.5. A man shovels dirt to plant a tree.

6. A Glacier slowly moves down a 6. A Glacier slowly moves down a mountain.mountain.

7. A tree’s roots grow into the 7. A tree’s roots grow into the cracks of rocks.cracks of rocks.

8. A major volcano erupts.8. A major volcano erupts.

9. A boy takes out the garbage 9. A boy takes out the garbage for his mother.for his mother.

10. A shovel is left outside and 10. A shovel is left outside and begins to rust.begins to rust.

Once you’ve answered these, discuss you’re answers with the rest of the class before you go

on.

Let’s Discuss The Questions.Let’s Discuss The Questions.

1. As the sand is moving there 1. As the sand is moving there is definitely erosion; there is is definitely erosion; there is also abrasion from the sand also abrasion from the sand gains colliding. gains colliding. BothBoth

2. This is frost wedging so it’s 2. This is frost wedging so it’s mechanical weathering. There mechanical weathering. There is no mention of movement. is no mention of movement. WeatheringWeathering

3. There is probably some 3. There is probably some weathering, but there is weathering, but there is definitely erosion. definitely erosion. Erosion or Erosion or BothBoth

4. Acid rain on a statue is 4. Acid rain on a statue is chemical weathering. This is chemical weathering. This is mainly mainly Weathering.Weathering.

5.Since the man is transporting 5.Since the man is transporting Earth materials, it’s Earth materials, it’s Erosion.Erosion.

6. A glacier moving down a 6. A glacier moving down a mountain would have both mountain would have both weathering and erosion. weathering and erosion. BothBoth

7. A tree’s roots growing into 7. A tree’s roots growing into cracks of rocks would be cracks of rocks would be weathering. weathering. WeatheringWeathering

8. A major volcanic eruption 8. A major volcanic eruption would involve both weathering would involve both weathering and erosion. and erosion. BothBoth

9. Unless the garbage has 9. Unless the garbage has “Earth Material” or dirt in it “Earth Material” or dirt in it there is probably no erosion or there is probably no erosion or weathering. weathering. NeitherNeither

10. The rusting of a shovel is 10. The rusting of a shovel is oxidation. This is chemical oxidation. This is chemical

weathering. weathering. WeatheringWeathering

Think you understand the difference?