Transcript weathering 06

Weathering
Topic 9
Regents Earth Science
Weathering

The break down of
rock material as a
result of chemical
and/or physical
action
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Physical weathering aka
mechanical weathering
 The
breakdown of rock into smaller
pieces without chemical change
1. Frost action

Weathering of rock
by the alternate
freezing and
thawing of water in
the pores or cracks
in the rock
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Frost
Wedging
2. Plant action

Occurs when cracks in rock are widened
by the forces exerted by growing plants
Plant Action
3. Pressure unloading
 Occurs
when rocks split along the
planes of weakness when the pressure
of overlying material is removed
 Usually occurs as the result of natural
processes such as landslides, erosion,
and earthquakes
 But humans also cause this through
quarrying and mining
4. Abrasion
 The
physical action of scraping,
rubbing, grinding, or wearing away of
rock surfaces due to the movement of
solid sediment in an erosional system
such as stream or wind
*As time increases, particles
become more rounded.*
5. Exfoliation
 The
scaling or peeling of successive
shells from the surface of rocks
 Generally occurs in coarse-grained
rocks that contain feldspar (like granite)
Pressure Unloading and
Exfoliation
Chemical weathering aka
decoposition
 The
breakdown of rock by chemical
action, during which there is a change in
chemical composition of the minerals in
the rock
The agents of chemical
weathering include
1. oxygen
 The
chemical reaction of oxygen with
another element is called oxidation
2. water
 Speeds
up chemical reactions
 Dissolves many materials
 Reacts directly with many mineral
substances (hydrolysis)
Caves form
3. Carbon dioxide
 Easily
dissolves in water to form
carbonic acid
 Calcite, limestone, and marble react
with carbonic acid
 Reaction of carbonic acid with other
substances is known as carbonation
Sinkhole
4. acids
 Produced
in the atmosphere by
lightning and on the surface by decay of
organic wastes
 Also gases released by people and
industry combine with water to form
acids