Weathering
Anticipation Guide #4 Ice wedging is a form of chemical weathering Erosion is the process where rocks are broken down The most active erosion agent on the planet is running water Gravity plays a role in all erosion except wind Rivers have 3 stages of development
VA SOL SOL 7 The student will investigate and understand geologic processes... Key concepts include b. processes ( weathering, erosion, deposition, and sedimentation) and their resulting features.
Objective 1 Summarize weathering as the process by which rocks are broken down by the action of water, air, and organisms. 2 Distinguish between physical (mechanical) and chemical weathering. 3 Recognize factors that affect the rate of weathering.
Enduring Understandings Weathering, erosion, and deposition are interrelated processes that form a cycle of forces that wear down and build up the Earth s surface.
Weathering Immediately after the first rocks on earth crystallized billions of years ago the process of weathering began to take effect to break them down again. http://www.uky.edu/as/geology/ho well/goodies/elearning/module07swf. swf
Weathering Weathering is the process by which rocks on or near the Earths surface break down and change
Weathering Erosion is the removal and transport of weathered material from one location to another. Materials are transported by moving water, ice or wind
Mechanical Weathering Before the agents of erosion can pick up and transport Earth materials, these materials must undergo some form of weathering.
Mechanical Weathering Mechanical weathering (also called physical weathering) is the process by which rocks and minerals break down into smaller pieces
Mechanical Weathering Mechanical weathering does not change the composition, only the size and shape of the rock
Mechanical Weathering Temperature plays a significant role in mechanical weathering.
Mechanical Weathering As water freezes it expands and will crack rocks
Mechanical Weathering Pressure is another factor in mechanical weathering as overlying layers of rock are removed the pressure is reduced and the exposed surface will expand and crack
Mechanical Weathering Exfoliation is the process by which the outer layers of rocks are stripped off
Chemical Weathering Exposed rocks can undergo changes in their chemical composition as well and result in the formation of new minerals and the release of dissolved substances.
Chemical Weathering Chemical weathering is the process by which rocks and minerals undergo changes in their composition due to chemical reactions
Chemical Weathering Water, carbon dioxide and acids are common agents
Chemical Weathering Hydrolysis is the reaction of chemical water with other substances
Chemical Weathering Oxidation is the chemical reaction of oxygen with other substances
Chemical Weathering Carbon Dioxide combines with water in the atmosphere to form carbonic acid that falls to the surface as precipitation
Chemical Weathering Carbonic acid reacts with minerals such as calcite in limestone and marble to dissolve rocks
Chemical Weathering Acid precipitation (acid rain) is another agent of chemical weathering caused by the oxidation of sulfur dioxide and nitrogen oxides released into the atmosphere by human activities
Chemical Weathering These gasses combine with water and oxygen in the atmosphere to form sulfuric and nitric acids. http://www.epa.gov/airmarket/aci drain/education/site_students/acid_a nim.html
Factors Affecting the rate of Weathering Natural weathering is a very slow process. Certain conditions and interactions can accelerate or slow the process significantly
Factors Affecting the rate of Weathering Climate is a major influence. The interaction between temperature and precipitation has the greatest effect on a region s rate of weathering
Factors Affecting the rate of Weathering Physical weathering rates are highest in cool, areas where water undergoes repeated freezing and thawing
Factors Affecting the rate of Weathering Chemical weathering rates are highest in areas with warm temperatures and abundant rainfall, and heavy vegetation
Factors Affecting the rate of Weathering Rock type and composition also affects the weathering rate. Some are quite resilient (Quartz) while some are easily broken down (Talc)
Factors Affecting the rate of Weathering Surface Area interacts with both mechanical and physical weathering as pieces break up through mechanical weathering more surface area is exposed for chemical weathering http://courses.soil.ncsu.edu/resource s/physics/texture/soilgeo.swf
Factors Affecting the rate of Weathering Topography is the shape and slope of the Earth s surface. Materials that lie on steep slopes are more likely to move and expose even more surface area