WEATHERING BY MS. HOUSTON ARMS 6 TH GRADE EARTH SCIENCE

Weathering  Natural process that breaks down rock into sediment (sand, silt, clay)  Begins the process of forming soil from rock and sediment.  Affects sediment particle size and soil texture.

Mechanical Weathering Burrowing Animals Ice Wedging Plant Roots Wind Water Physical process that breaks down rock but does not change the composition of rock.

Mechanical Weathering  Ice wedging is the process that occurs when water freezes, expands and thaws in the cracks of a rock  Overtime the cracks will get wider and deeper and the rock will break  Plant growth causes rock to break by roots exerting pressure on the rock  Plant roots can seek their way into rock cracks and continue to grow creating pressure in the cracks of rock.

Mechanical Weathering  Burrowing animals dig tunnels in the ground loosening small rocks and sediment and eventually pushing them to the surface  Wind carries other sediment and potentially beat on the surface of other rock loosening or breaking other rock  Water can exert pressure on sediment and small rock thereby further breaking the rock.

Chemical Weathering  Chemical process that breaks down rock by chemical reactions that dissolve minerals or change them into different minerals.  Rock composition will change!  Carbonic acid  Natural plant acids  Oxidation  Acid rain

Chemical Weathering- Natural Acids  Carbonic acid forms when water reacts w/ carbon dioxide gas in the air.  Carbonic acid is a weak acid that can dissolve some minerals found in rock.  Carbonic acid dissolves calcite a mineral found in limestone  Ex: cave formation  Other natural acids can dissolve the mineral feldspar which is found in granite, some types of sandstone and other rocks.  Kaolinite is a clay mineral found in some soil and is formed from dissolved (broken down) feldspar.

Chemical Weathering- Plant Acids and Oxidation  Plant roots give off acids  These acids can dissolve some minerals found in rock making the rock weak and causing the rock to break into smaller pieces  Oxidation occurs when oxygen gas and moisture react with certain materials to form a new material  This new material looks like rust.  Oxidation of minerals gives some rock a red or rust color

Effects of Climate and Rock Type  Climate affects the rate (how fast) weathering occurs  Cold, polar climates increases MECHANCAL weathering  Warm, wet climates increases CHEMICAL weathering  Desert climate slows CHEMICAL weathering  Cold, polar climates slows CHEMICAL weathering

For Additional Information: See the Glencoe textbook. You may access the textbook online via the ARMS website. Click on Academics Click on Science Information Click on Online Textbook and look for the 6 th Grade textbook. Highlight and copy the code Click on the 6 th grade textbook and paste t he code the click submit. If you can not access the book, make sure that you have the latest version of Adobe reader then repeat the steps