Download Weathering Weathering - Surface processes that work to break

Weathering
Weathering - Surface processes that work to break down rock and the earth’s surface
Weathering breaks rock into smaller pieces such as sand (largest), silt (medium), and
clay (smallest).
Mechanical Weathering – occurs when rocks are broken apart by physical process.
The overall chemical makeup (composition) of the rock stays the same.
2 Processes
1) Plants and Animals
 Roots can cause cracks in rocks
 Burrowing animals can loosen sediment and push it to the surface
2) Ice Wedging
 Occurs in temperatures and cold climates where water enters cracks in
rock and freezes
 Water expands when it freezes causing cracks to enlarge or breaks apart
rocks
 The ice then melts allowing more water to enter the cracks
 Common in mountains where warm days and cool nights occur
Chemical Weathering – occurs when chemical reactions dissolve or alter the minerals
in rocks or change them into different minerals. Changes the chemical composition
1) Natural Acids – Carbonic acid reacts with minerals such as calcite, which is the
main mineral that makes up limestone. Over many thousands of years,
carbonic acid has weathered so much limestone that caves have formed
2) Plant Acids – Some roots and decaying plants give off acids that also dissolve
minerals in rock. When the mineral dissolves, the rock is weakens and the rock
breaks into smaller pieces.
3) pH Scale – the strength of acids and bases
4) Oxidation – occurs when some materials are exposed to oxygen and water
 Materials high in iron will rust
 Can give rock layer a red color
Soil Erosion
Soil Erosion – Soil erodes when it is move from the place where it formed. Erosion
occurs as water flows of Earth’s surface or when wind picks up and transports
sediment.
Causes and Effects of Soil Erosion
1. Agriculture Cultivation – if topsoil erodes rapidly the nutrients are removed
2. Forest Harvesting – when forests are removed, soil is exposed and erosion
increases
3. Overgrazing – Farm animals graze fields until almost no ground remains
4. Excess Sediment – Eroded soil is removed to a new location where it is
deposited
Preventing Soil Erosion
No-Till Farming – plant stalks are left in the field after
harvesting and the next year’s crop is planted within the stalks
without plowing.
Contour Farming – planting along the natural contours of the
land to reduce soil erosion.
Terracing – farming method used to reduce erosion