WELCOME BACK!

Do Now For Monday, Jan. 7th 2013

-WRITE AT LEAST TWO FULLSENTENCES-Use your memory and your common knowledge to describe the difference

between weathering and erosion

GUIDED NOTES FOR 7 -1ROCKS AND WEATHERING

• Weathering – The process that breaks down rock and other substances at Earth’s surface.– Heat, cold, water and ice – CO2, & O2 contribute to

weathering.

– Ontario, CA

Erosion is the MOVEMENT of rock particles by wind, water ice or gravity.• Erosion is the process that wears away surface

materials and moves them from one place to another.

Mechanical Weathering – The process that breaks rock into smaller pieces while the rock’s

composition remains the same.

• Five types of mechanical weathering:– Freezing and thawing – (Ice wedging) – Release of pressure– Plant growth– Abrasion – Animal action

Ice Wedging is the freezing and thawing of water in cracks in rock

Release of pressure happens when erosion below rock causes it to crack and flake off.

Ontario, CA

Another example of pressure release is a famous 8,800 ft. mtn. in Yosemite National Park. (Half Dome)

Plant Growth refers to tree and other plant roots prying apart cracked rocks as they grow.

Abrasion happens when sand and rock particles scrape and wear away rock surfaces like

sandpaper on wood.(Ohio)

Animal action loosens and breaks apart rocks in the soil.

• *

Chemical Weathering!

• The process that breaks down rock through chemical changes.

• Chemical weathering alters (changes) the composition of the rock.

• As chemical weathering occurs, the new rocks are made up of different minerals than before.

• Many times, mechanical weathering breaks rock into smaller pieces creating greater surface area for easier chemical weathering.

Four Types of Chemical Weathering!

• Water or Hydrolysis• Oxidation • Carbonic Acid or Carbonation • Plant roots

Water or Hydrolysis –Water dissolves certain types of rock.

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Clay is a product of hydrolysis of rock.

Oxidation – O2 in the air plus iron in the rock may cause rust, which weakens the rock’s structure.

• .

Carbonic Acid or Carbonation – CO2 in the air and rainwater combine to produce a weak acid (acid rain) that dissolves some types of rock.

Plant Growth – Trees, plants and lichen produce weak acids that dissolve the rock they touch.

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Rate of Weathering is affected by two factors!

• Type of Rock: Rocks that are more permeable weather faster. Permeable rock has tiny air spaces that allow water to seep in.

• Climate: In hot and wet climates, rock weathers faster.

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