1. EQ: What is chemical and mechanical weathering?
Rocks and Weathering
EQ: What is chemical and mechanical weathering?
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2. EQ: What is chemical and mechanical weathering?
Weathering – process that breaks up rocks on the Earth’s surface
2 Types: mechanical (physical) and chemical
Causes: heat, cold, water, ice, oxygen, carbon dioxide
Erosion – movement of rock particles by wind, water, ice or gravity
EQ: What is chemical and mechanical weathering?
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3. Mechanical Weathering
Mechanical weathering – rock is physically broken into smaller pieces
Caused by heating and cooling, freezing and thawing, growth of plants, actions of animals, and abrasion
Abrasion- grinding away of rock by rock particles carried by water, ice, wind or gravity
Works slowly , over long periods of time.
EQ: What is chemical and mechanical weathering?
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4. Mechanical Weathering
Ice wedging
Water seeps into a crack in the rock, freezes (expands) and thaws (contracts) repeatedly
Pieces begin to crack
EQ: What is chemical and mechanical weathering?
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5. EQ: What is chemical and mechanical weathering?
Chemical Weathering
Chemical Weathering – breakdown of rock through chemical changes.
5 agents: water, oxygen, carbon dioxide, living organisms, and acid rain
Produces a different mineral makeup from the rock they came from
i.e. – granite begins with minerals of feldspar, quartz and mica. After chemical weathering, granite changes feldspar to clay
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6. EQ: What is chemical and mechanical weathering?
Chemical Weathering
Creates holes or soft spots in the rock.
Chemical and mechanical weathering often work together.
Mechanical breaks apart rock,
More surface area for chemicals to work!
EQ: What is chemical and mechanical weathering?
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7. 5 Agents of Chemical Weathering
Water – most important! Dissolves rock.
Oxygen – combines with iron in the presence of water (OXIDATION). Causes rust. Makes the rock crumbly, gives it a red/brown color.
Carbon dioxide-found in air. Mixes water and forms carbonic acid. Weathers marble and limestone.
EQ: What is chemical and mechanical weathering?
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8. 5 Agents of Chemical Weathering
Living organisms – plant roots produce a weak acid that slowly dissolves rock.
Acid Rain – fossil fuels pollute air with sulfur, carbon, and nitrogen compounds. The compounds mix with cloud vapor to form acid.
EQ: What is chemical and mechanical weathering?
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9. EQ: What is chemical and mechanical weathering?
Rate of Weathering
Two factors that determine the rate
Type of Rock –
What is it made of?
Is the rock permeable?- full of tiny, connected air spaces that allow chemicals to seep through it
Climate
weather conditions
Hot and wet climates weather rock more quickly
EQ: What is chemical and mechanical weathering?
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10. Class Work and Homework
Fill In What did I learn Confused Say Rock Shake Page G46 Read pages G 40 – G 45, #’S 1-5
EQ: What is chemical and mechanical weathering?
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