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 Organic activity- plants and animals (Plant roots, Animal activity burrowing, moving soil) Abrasion Exfoliation

Ice Wedging

Plant Roots (organic activity)

Animal Activity (Organic activity)

Abrasion The 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. NOT SEEN IN ALABAMA

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- important in soil formation

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 characterized by caves and sinkholes.

Features of Karst: Sinkholes

Features of Karst: Caves

Features of Karst: Disappearing Streams

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 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.

Climate

Human Activity Mining, Construction, Transportation, Recreational activities all contribute to wearing away and eroding rocks

Topography The 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.