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Chapter 5: Section 1. Weathering . Weathering. Mechanical Rocks are broken from large pieces into smaller ones. Temperature Frost-Action Organic Activity Gravity Abrasion. Chemical Changes occur in mineral composition. Water Oxidation Carbonation Sulfuric Acid Plant Acids. VS.
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Chapter 5: Section 1 Weathering
Weathering • Mechanical • Rocks are broken from large pieces into smaller ones. • Temperature • Frost-Action • Organic Activity • Gravity • Abrasion • Chemical • Changes occur in mineral composition. • Water • Oxidation • Carbonation • Sulfuric Acid • Plant Acids VS. The breaking down of Earth’s surface.
M.W. #1. Temperature • During the day, rocks are heated by radiation. • Outer layer of rock heats up and expands slightly. • Inside layers stay cool and do not expand. • At night, outside layer cools and contracts. • This process continues, and as it does pieces of rock on outside layer flake off. • Exfoliation- Flaking off of rocks into shards.
Changes in Temperature cause Exfoliation Mechanical (Physical)
M.W. #2 Frost Action Unlike most liquids, water expands when changing from a liquid to a solid (water to ice). The repeated freezing and thawing allows water to creep further and further into the rock when cracks expand. Eventually rocks crack and break off.
Frost Action: Freezing and Melting of Water (Ice Wedging) Mechanical (Physical)
M.W. # 3 Organic Activity Root-pry- Roots of plants, usually trees pry apart a rock as roots grow.
M.W. # 4 Gravity Landslide #1 Land Slide # 2 Gravity loosens material and causes it to fall. When it does, it collides with other rocks causing them to break and fall causing landslides.
M.W. # 5 Abrasion Abrasion- Wind blown sand causes weathering of rocks. Water can do the same as it carries sand and rocks.
C.W. #1 Water As water runs over a surface it dissolves the minerals that hold rocks together. Water can also form acids when mixed with gases in the air ( acid rain ).
C.W. #2 Oxidation When oxygen combines with another substance to form a completely different substance. Iron in rocks combines with oxygen to form rust.
C.W. # 3 Carbonation When carbon dissolves into water, carbonic acid forms (Gives soda the fizz). Can dissolve limestone and feldspar.
C.W. # 4 Sulfuric Acid When sulfur dissolves in water (usually water vapor) it can form sulfuric acid which breaks down brick buildings and old gravestones.
Plant Acids Plants produce a weak acid that can break down the minerals in rocks as well.