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Mechanical weathering
Ice and water
frost wedging – water seeps into cracks in rock. It expands when it freezes causing the crack to expand. When this occurs over and over rocks can break into smaller pieces.
• http://www.classzone.com/books/earth_science/terc/content/visualizations/es1201/es1201page01.cfm
Chemical weathering
Hydrolysis
as water leeches through the soil it picks up ions that are
often deposited
in caverns below.
Oxidation
when oxygen reacts with rock outcrops, breaking them down.
This process usually
produces rust.
Rates of Weathering
• Surface Exposure– More surface area more weathering
• Composition of rock– Some rocks weather better than others
• Climate– Some climates are more conducive to
weathering
How soil forms
Soil
loose weathered rock and organic matter.
Parent material
the material in which soil is formed from.
Where soil comes from
• Residual soil– Soil that sits above the bedrock it was formed
from
• Transported soil– Soil that has been transported to a new
location
• Soil profile– A cross section of the soil that makes up a
particular area.
• Soil horizons– The individual zones or layers that make up
the soil profile
Types of soil
• Topsoil– A horizon, top layer dark in color, and it
contains humus (organic matter)
• Subsoil– B horizon, red or brownish due to greater iron
content, contains clay
• C horizon– Older more weather layer, larger fragments of
rock
Mass movement vs. erosion
• Mass movement is the downhill transportation of material caused by gravity.
• Erosion is the transportation of material due to wind or water.
Mass movement
Landslide – the mass movement of bedrock downhill
Talus – weathered rock
fragments that have been
pulled downhill
Earthflow vs. Mudflow
• Earthflow is a landslide that occurs in water saturated areas.
• Mudflow is a massive movement of water downhill that contains high amounts of clay and silt.
Soil fertility
Soil fertility is the ability for soil to grow plants.
The amounts of minerals, water, and organic matter determine what plants are able to survive in that particular area.
Soil depletion occurs when soil gradually looses its nutrients and can no longer sustain crops.
How can we prevent this from happening?
Salinization is when irrigation brings in minerals that can add salt deposits to the soil decreasing its fertility.
Strip-cropping is a method where farmers alternate different types of crops. Some maybe tall crops like corn while others are ground covering crops like alfalfa.