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Lecture 9

GEOG 1120 Lecture Notes - Lecture 9: Chert, Mafic, Ripple MarksPremium

5 pages38 viewsFall 2016

Department
Geography
Course Code
GEOG 1120
Professor
John Martin
Lecture
9

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Lecture 9: Weathering and SED Rocks
I. Intro
- Contain fossils.
- Important economics: Soil, oil.
- Rock cycle:
A. Sedimentary rocks
B. Metamorphic rocks
C. Igneous rocks
D. Sediments
- Hardness: Hard rocks will weather slowly, soft minerals will
weather quickly due to solubility and oxidation potential
(Felsic oxides very fast).
- Silicates can be summarized using Bowen's DSI (Olivine weather
very quickly, Quartz the strongest).
II. Mechanic Weathering
- Physical breakdown of rocks.
1. Frost Wedging - requires water and temperature of zero (once
there is a crack in the rock, water gets in and freezes).
2. Root Wedging
3. Unloading/Exfoliation - rock forms deep in Earth and in under
pressure and when it expands, it results a fracture.
- Do not move the rocks, they breakdown on their own.
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- When they physically weather, they rare angular shape.
- The process of rock breakdown cannot be stopped.
III. Chemical Weathering
- Chemical breakdown of rocks.
1. Dissolution - some minerals are soluble and dissolve in water.
=> Ex: Halite dissolves quickly but rocks do dissolve in
water slowly.
=> Halite is the most susceptible to dissolution.
2. Oxidation - most commonly Fe(2+) with O and H2O to form
Fe(3+).
=> The Oxides are the most susceptible to oxidation.
3. Hydrolysis - results in the production of ions, give it's
dull appearance.
- Mafic rocks cannot be stopped from rusting.
- Rates of Weathering:
=> Three main factors:
A. Mineralogy
B. Climate
C. Process
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