weathering+and+erosion

=Weathering, Soils and Mass Movement=


 * Weathering and Erosion** – [|Over time], the surface of all rocks begin to break down. __Weathering__ is the break down of rocks that have been exposed to the atmosphere. Once the rocks are broken down, the pieces are transported from one place to another. This process is called [|erosion]. Erosion is caused by wind, moving water (streams, waves, ocean currents), ice (glaciers), and by gravity.
 * Most erosion that takes place on Earth is caused by moving water.
 * __Types of Weathering__** -
 * //Mechanical weathering// – is the breaking down of rocks into smaller pieces __without__ changing their composition (what they’re made of).
 * //Chemical weathering// – is the breaking down of rocks as their minerals __change__ in composition (they become different substances).
 * __Types of Mechanical Weathering__** -


 * //Ice wedging/frost action// – water enters small cracks in the rock. When it freezes, it __expands__ and forces the crack to open more. The process repeats over again until the rock breaks apart.
 * //Wetting and drying// – breaks up rocks that are made from clay. When they are wet they expand, and they shrink as they dry. As this repeats over and over, the clay becomes weak and cracks (think of all the projects you have made out of clay…they all crack and fall apart)!
 * //Exfoliation// – soil and rock is removed (glaciers or uplifting), exposing rock found deep underground. This releases the pressure causing the __surface__ of the rock to expand and eventually crack.

Types of Chemical Weathering –

 * //Hydrolysis// – [|water] (hydro) reacts with minerals such as feldspar and form clay.
 * //Oxidation// – oxygen reacts with some minerals, especially those containing iron (magnetite) to form __rust__ (called iron oxide). This occurs faster with water!
 * //Carbonic acid// – carbon dioxide (CO²) dissolves in water to form this acid. It can cause minerals to dissolve, especially those containing calcite!

Weathering Rates – Many factors affect the rate of weathering. They are:
1. The rock’s resistance to weathering (hardness). 2. The amount of surface area (LAB). 3. Climate a. Chemical weathering occurs faster in warm, wet climates. b. Mechanical weathering occurs faster in cold or dry climates. Soil is formed from weathered rock and organic material called //__humus__//. The material from which the soil is formed is called the __parent material__. If the parent material is the underlying bedrock, it is called __residual soil__ (residue is a substance that is left behind, so residual soil is soil that is left over after the bedrock has been weathered)! If the soil was formed in one place and then carried someplace else by wind, water, glaciers, etc.,then it is called __transported soil__.
 * __Soil Formation__** –
 * much of the soil in New York is transported soil left behind by the glaciers.**

__Soil Profile__ **- This is a cross-section of the layers of soil. Each layer is called a horizon.** Test yourself [|here].

__Mass Movements__ **– These are movements of loose Earth materials caused by the force of gravity. //Creep//- a very slow downward movement of the soil. Only noticeable by the results of fence posts and telephone poles tilted downhill. //Landslide// – is a sudden movement of material downhill (usually a very steep slope). //Avalanche// – landslide made up of ice and snow as well as soil. //Slump// – small areas of land move downhill (usually a short distance) – especially along roadways that cut into the side of a hill. //Mudflow// – A very fast and dangerous movement of water saturated soil.**

__Soil Conservation__– Topsoil is the nutrient rich portion of the soil that is necessary for growing crops. It is important to prevent the erosion of this non-renewable resource (takes very long to form and replace). Methods used to slow soil erosion: Windbreaks Contour farming Strip cropping No-till farming