Weathering and Erosion
Weathering
• The breakdown of the materials of Earth’s crust into smaller pieces.
Mechanical Weathering
• Process by which rocks are broken down into smaller pieces by physical means.
• Types of Physical weathering– Ice wedging– Plant roots– Animal activity (burrowing, moving soil)– Abrasion– Exfoliation
Ice Wedging
Ice Wedging
Plant Roots
Animal Activity
AbrasionThe scraping of materials together
Exfoliation• As pressure reduces on exposed rock, the
granite expands, resulting in long curved cracks and layers that peel away from the rock
Chemical Weathering
• The process that breaks down rock through chemical changes.
• The types of chemical weathering– Carbonation– Hydrolysis– Oxidation
Hydrolysis
• The interaction of water with other substances to weather rock
Oxidation• Iron combines with
oxygen in the presence of water in a processes called oxidation
• The product of oxidation is rust
Carbonation
• CO2 dissolves in rain water and creates carbonic acid
• Carbonic acid easily weathers limestone and marble
Carbonation, Continued
• Chemical weathering of limestone, breakdown of calcite
• Results in Karst Topography - A type of landscape in rainy regions where there is limestone near the surface, characterized by caves, sinkholes, and disappearing streams.
Features of Karst: Sinkholes
Features of Karst: Caves
Features of Karst: Disappearing Streams
Living Organisms
• Compounds from burning coal, oil and gas react chemically with water forming acids.
• Acid rain causes very rapid chemical weathering
Acid Rain
Erosion
• The process by which water, ice, wind or gravity moves fragments of rock and soil.
Water Erosion
• Rivers, streams, and runoff
Ice Erosion
• Glaciers
Wind Erosion
Mass Movements (Gravity)
• Landslides, mudslides, slump and creep, talus
landslide clip.mpeg
Talus
• Rocks at the base of a slope deposited by gravity
Rates of Weathering
How quickly or slowly a rock weathers and erodes depends on several factors:•Rock Composition•Exposure•Climate•Topography•Human Activity
Rock Composition
Some rocks are more resistant to weathering. For example, rocks comprised of quartz are more resistant to weathering since quartz is so stable, having crystallized last from the magma chamber.
Human Activity
Mining, Construction, Transportation, Recreational activities all contribute to wearing away and eroding rocks
TopographyThe elevation and slope of the land surface affects
its rate of weathering, for example:• Colder temperatures at higher elevations, more
ice wedging• Low elevations – more erosion by wave action• Steep slopes more affected by gravity
Exposure
• The more rock exposed, the more weathering can occur, so the rate of weathering increases.