Presentation on theme: "EQ: What is chemical and mechanical weathering?"— Presentation transcript:
1 EQ: What is chemical and mechanical weathering? Rocks and WeatheringEQ: What is chemical and mechanical weathering?
2 WeatheringWeathering – process that breaks up rocks and other substances at the Earth’s surfaceTwo types of weathering, mechanical and chemicalHeat, cold, water, ice, oxygen and carbon dioxide contribute to weatheringErosion – movement of rock particles by wind, water, ice or gravity
3 Mechanical Weathering Mechanical weathering – rock is physically broken into smaller piecesCaused by heating and cooling, freezing and thawing, growth of plants, actions of animals, and abrasionAbrasion- grinding away of rock by rock particles carried by water, ice, wind or gravityWorks slowly , over long periods of time. Eventually wears away whole mountains
4 Mechanical Weathering Ice wedgingOccurs in cold climatesWater seeps into a crack in the rock, freezes (expands)and thaws (contracts) repeatedlyThis process expands the rock slowly and pieces crack off
5 Chemical WeatheringChemical Weathering – process that breaks down rock through chemical changes.Agents are water, oxygen, carbon dioxide, living organisms, and acid rainProduces a different mineral makeup from the rock they came fromi.e. – granite begins with minerals of feldspar, quartz and mica. After chemical weathering, granite changes feldspar to clay
6 Chemical WeatheringCreates holes or soft spots in the rock allowing it to break apart more easilyChemical and mechanical weathering often work together.Mechanical weathering breaks apart rockThis 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 solutionOxygen – 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 limestoneLiving organisms – as plant roots grow they produce a weak acid that slowly dissolves rock around the rootsAcid 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 rockIs the rock permeable – full of tiny, connected air spaces that allow chemicals to seep through itClimateAverage weather conditions of an areaHot 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