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Rocks and Weathering EQ: What is chemical and mechanical weathering?

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Presentation on theme: "Rocks and Weathering EQ: What is chemical and mechanical weathering?"— Presentation transcript:

1 Rocks and Weathering EQ: What is chemical and mechanical weathering?

2 Weathering Weathering – process that breaks up rocks and other substances at the Earth’s surface – Two types of weathering, mechanical and chemical – Heat, cold, water, ice, oxygen and carbon dioxide contribute to weathering Erosion – movement of rock particles by wind, water, ice or gravity

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. Eventually wears away whole mountains

4 Mechanical Weathering Ice wedging – Occurs in cold climates – Water seeps into a crack in the rock, freezes (expands)and thaws (contracts) repeatedly – This process expands the rock slowly and pieces crack off

5 Chemical Weathering Chemical Weathering – process that breaks down rock through chemical changes. – Agents are 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 ntent/visualizations/es1202/es1202page01.cfm

6 Chemical Weathering Creates holes or soft spots in the rock allowing it to break apart more easily Chemical and mechanical weathering often work together. – Mechanical weathering breaks apart rock – This process exposes more surface area of the rock to chemical weathering

7 Five agents of Chemical Weathering Water – most important agent of chemical weathering. Wears away rock by dissolving the rock, mixing it uniformly to make a solution Oxygen – combines with iron in the presence of water. This is oxidation. Causes rust. This process makes the rock crumbly and gives it a red or brown color

8 Five agents of Chemical Weathering Carbon Dioxide – found in our air. Dissolves in water and forms a weak acid called carbonic acid. Weathers marble and limestone Living organisms – as plant roots grow they produce a weak acid that slowly dissolves rock around the roots Acid Rain – cause is burning fossil fuels that pollute air with sulfur, carbon, and nitrogen compounds. The compounds mix with cloud vapor to form acid.

9 Rate of Weathering Two factors that determine the rate – Type of Rock – Depends on the minerals that make up the rock Is the rock permeable – full of tiny, connected air spaces that allow chemicals to seep through it – Climate Average weather conditions of an area Hot and wet climates weather rock more quickly

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


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