Weathering SWBAT distinguish between weathering and erosion; identify the variables that affect the rate of weathering

What do you think created the cracks in the rock to form? Where did the smaller rocks come from?

Get your Lab notebooks In your group read through the discovery lab on page 153. Title and date your lab Send one person from your group to gather the supplies Complete the observe section in your lab notebook. Write your answers in complete sentences!!

Weathering Weathering –The process that breaks down rocks on Earth’s surface Erosion –The removal and transport of materials from one location to another Mechanical weathering –Physical weather – the process by which rocks and minerals break down into smaller pieces

Mechanical Weathering What are the 2 big factors in mechanical weathering? –Temperature When water freezes it expands, which can expand cracks –Pressure Buried rock is under pressure. When the pressure is removed, it can expand creating cracks. Frost wedging –The repeated thawing and freezing of water in the cracks of rocks Exfoliation –The process that strips away the outer layer of a rock

Chemical Weathering Chemical weathering –The process by which rocks and minerals undergo changes in their composition as a result of a chemical reaction

Agents of Chemical Weathering Water Oxygen Carbon Dioxide Acid Precipitation Can dissolve many kinds of minerals and rocks. Acts as a medium for other reactions Can combine with other substances to create reactions When combined with water in the atmosphere it forms a weak acid that can dissolve certain rocks and minerals Caused by the oxidation of sulfur dioxide and nitrogen oxides that are released in the atmosphere by human activities

Agents of Chemical Weathering Water –Hydrolysis The reaction of water with other substances Oxygen –Oxidation The chemical reaction of oxygen with other substances

What affects the rate of weathering? Climate –Precipitation, temperature, and evaporation influence the rate of chemical weathering. –Chemical weathering happens in areas with warm temperatures, abundant rain, and lush vegetation –Physical weathering happens in cool, dry areas, where water is more likely to freeze and thaw repeatedly

What affects the rate of weathering? Rock Type and Composition –Sedimentary are more easily weathered than other types –Igneous rocks are harder and more resistant to weathering

What affects the rate of weathering? Surface Area –Mechanical weathering breaks rocks into smaller pieces, increasing surface area –The more surface area, the more weather can break it down

What affects the rate of weathering? Topography and other variables –Materials on slopes are more easily eroded, due to gravity –Decaying materials give off carbon dioxide which when combined with water creates an acid that aids in weathering

In your Groups Individually record the answers to questions 1-4 on page 161 Turn in your individual work by the end of the period