Transcript Weathering

Aim: What is weathering?
I. Weathering – the breakup of rock
due to exposure to the atmosphere.
A. Erosion – is the removal and transport of
earth materials by agents (streams, rivers,
glaciers, wind, waves and currents, and
gravity)
B. Two types of weathering:
1. Mechanical (physical) weathering –
occurs when rock is broken or split into
smaller pieces of the same material without
changing its composition.
a. Ice wedging (frost action) – when freezing
water causes rocks to crack
b. Ice heaving – when water in ground
freezes and lifts the pavement above it.
c. Wetting and drying – especially effective at
breaking up rocks that contain clay.
d. organic activity (Plants and animals)
i. plants’ roots may grow through rocks
ii. Ants, earthworms, woodchucks dig holes and
expose bedrock to atmosphere.
2. Chemical Weathering (Decomposition) –
occurs when the minerals are changed into
different substances due to rainwater, oxygen,
carbon dioxide, and acids of plant decay.
a. Hydrolysis – reaction of water with other
substances.
b. Oxidation – the chemical reaction of oxygen
with other substances (iron bearing materials are
most easily affected – rust or iron oxide).
c. Carbonic acid – weak acid formed from
carbon dioxide dissolving into water.
•Carbonation – when some minerals react with carbonic acid
to form a new product. (underground caverns).
Examples of Physical weathering
http://www.classzone.com/books/earth_science/terc/content/visu
alizations/es1201/es1201page01.cfm?chapter_no=visualization
Example of Chemical weathering
http://www.classzone.com/books/earth_science/terc/content/vis
ualizations/es1202/es1202page01.cfm?chapter_no=visualizatio
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