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Weathering How are the earth’s surfaces changed?
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Weathering How are the earth’s surfaces changed?.

Jan 17, 2016

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Marcus Richards
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Page 1: Weathering How are the earth’s surfaces changed?.

Weathering

How are the earth’s surfaces changed?

Page 2: Weathering How are the earth’s surfaces changed?.

Weathering is the breaking down of rocks and other materials on the earth’s surface.

There is no change in the rock’s chemical make-up or composition with this.

Page 3: Weathering How are the earth’s surfaces changed?.

There are two types of weathering.

Page 4: Weathering How are the earth’s surfaces changed?.

Types of Weathering

Mechanical or physical weathering ~ causes:

Temperature changes causing ice or frost wedging

Root, organic, or biological weatheringGravity Abrasion (scraping or sanding)Unloading or exfoliating (like peeling)

Skip ahead to details…

Page 5: Weathering How are the earth’s surfaces changed?.

Second Type of Weathering

Chemical or physical weathering ~causes:

Water wears down rocksAcid dissolves Earth’s surfacesAir pollution Plant chemicalsOxidation (exposure of minerals to

oxygen)

Page 6: Weathering How are the earth’s surfaces changed?.

Mechanical and chemical weathering can work together…

Advance to chemicalweathering

Page 7: Weathering How are the earth’s surfaces changed?.

Causes of mechanical weathering include:

Temperature: which causes cycles of expansion and contraction

Mechanical or physical weathering

Page 8: Weathering How are the earth’s surfaces changed?.

Ice or frost wedging (frost action, freeze-thaw cycle): when liquid water goes into cracks and then freezes causing the cracks to get wider

Mechanical/physical weathering

Page 9: Weathering How are the earth’s surfaces changed?.

The power of the freezing and warming cycle

Page 10: Weathering How are the earth’s surfaces changed?.

More mechanical orphysical weathering

Organic activity root-pry, burrowing animals, human activities

Page 11: Weathering How are the earth’s surfaces changed?.

A hearty growing plant can expand a crack in a rock until it splits!

CRACK!

Roots can also raise up cement slabs, crack sewer lines, and house foundations. Don’t you think they could also crack a rock?

Page 12: Weathering How are the earth’s surfaces changed?.

Gravity causes rocks to fall and collide with other rocks

Mudslides and sinkholes…

Page 13: Weathering How are the earth’s surfaces changed?.

Landslides, rockslides,holes, and cracks

Page 14: Weathering How are the earth’s surfaces changed?.

Abrasion: wearing away by solid particles

Wave rock, Australia – carved by wind blown sand.

Phoenix, AZ

Page 15: Weathering How are the earth’s surfaces changed?.

Unloading: the expanding of high pressure rock when exposed to a lower pressure

Classic sheeted granite in Yosemite National Park. It is broken into gently dipping plates by unloading joints.

Page 16: Weathering How are the earth’s surfaces changed?.

Exfoliation or unloading - rock breaks off by layers or sheets along joints parallel to the ground surface; caused by expansion of rock due to uplift and erosion; removal of pressure of deep burial

Page 17: Weathering How are the earth’s surfaces changed?.

Extreme exfoliation!

Page 18: Weathering How are the earth’s surfaces changed?.

Contraction due to crystallization

The surface pattern on this pedestal rock is honeycomb weathering, caused by salt crystallization. This example is on the island of Taiwan.

Salt weathering of building

stone on the island of Gozo, Malta

Back to overview

Page 19: Weathering How are the earth’s surfaces changed?.

The other kind of Weathering~

Chemical Weathering

The altering of the composition or the make-up of minerals within a rock that results in a reduction

in size.

Page 20: Weathering How are the earth’s surfaces changed?.

Agents of chemical weathering include:

Water: Dissolves minerals out of rocks making them weaker.

Example:

Page 21: Weathering How are the earth’s surfaces changed?.

Acid: Dissolves minerals in rocks (examples: carbonic acid, acid rain, and plant acid)

Cave wall

Chemical weathering

Page 22: Weathering How are the earth’s surfaces changed?.

Lichens such as these growing on the rocks in the pictures can produce weak acids that react with the rock.

Page 23: Weathering How are the earth’s surfaces changed?.

Air polllution can produce acid rain.

Page 24: Weathering How are the earth’s surfaces changed?.

3000 year old Egyptian Obelisk

3000 year old Egyptian Obelisk after 100 years in NY

Picture it…

Page 25: Weathering How are the earth’s surfaces changed?.

The ancient Parthenon in Greece shows discoloration and chemical weathering

effects just from air pollution and acid rain.

Page 26: Weathering How are the earth’s surfaces changed?.

Oxidation: Oxygen combines with iron minerals and sulfur minerals changing the composition of the rock

More chemical weathering

Oxidation turned these rocks in Nevada's Valley of Fire red.

Page 27: Weathering How are the earth’s surfaces changed?.

Look at factors that hasten weathering:

1. How much surface area is exposed to the elements?

Page 28: Weathering How are the earth’s surfaces changed?.
Page 29: Weathering How are the earth’s surfaces changed?.

2. Climate:

Warm, wetclimates +

chemical weathering breaks down rocks rapidly, too.

Mechanical

weathering

+ cold climates break down rocks rapidly.

Page 30: Weathering How are the earth’s surfaces changed?.

3. Topography: the position of the rock (Is it in a position where gravity can pull it down?)

4. Air pollution

5. Exposure time (Will the elements have time to break down the surface?)

Mechanical and chemical weathering work together to break down rocks and our earth surface.

Page 31: Weathering How are the earth’s surfaces changed?.