GEOL 106 Lecture Notes - Sulfuric Acid, The Dead C, Fluorine

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Published on 23 Nov 2011
School
Queen's University
Department
Geological Sciences and Geological Engineering
Course
GEOL 106
Professor
Read Chapter 3 in Textbook (pages 72 to 107)
Do Risk Analysis and Risk Management
Volcano “Zones”
1. Constructive (ie. Divergent) Plate margins
2. Destructive (ie convergent) Plate margins
3. Hot Spots
most commonly not at plate boundaries (eg. Hawaii)
both oceanic and continental
Dealing with volcanic risk
We first need to consider the nature of Magma of different
compositions
Chemical composition
Magma differ in the proportion of elements
o Results in rocks of different colours
o And magmas with different properties
More Si+O More Fe+Mg
Less Fe+Mg Less Si+O
Rock is Whiter/Pinker -> Felsic Rock is blacker -> Mafic
Eg. Rhyolite Eg. Basalt
Magmas
Felsic
Intermediate
Mafic
High Viscosity
Intermed Viscosity
Low Viscosity
High Si
Intermed Si
Low Si
High H20 (>5%)
Intermed H2O (1 to
5%)
Low H2O (<1%)
Viscosity
A measure of the ease with which a fluid flows
Low Viscosity -> flows easily eg. Water
High Viscosity -> does not flow easily eg. Tar or molasses
IMPORTANT NOTE
Magma contains dissolved gases (eg. H20 (water), CO2
(carbon dioxide) ,SO2 (sulphur dioxide) ,F (fluorine) ,Cl
(chlorine))
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H2O is the dominant one
Magma
When it comes out of the ground will be in one of the two
forms
o 1. Lava (liquid)
o 2. Pyroclastic material (hot particles)
Reaches the surface by coming through either
o 1. Fractures (fissures)
ie. Cracks (where a dyke reaches surface)
mostly involve mafic lave (ie. Basalt)
results in extensive lava sheets
due to low viscosity (eg. Iceland)
These are calm eruptions
o Dangers of fissure eruptions
Generally quite safe
But major eruptions can generate atmospheric
effects from SO2 gas and CO2 gas release (eg.
Laki eruption in Iceland)
In particular, enormous flood basalt events may
be catastrophic
Linked to mass extinctions (eg, 65 mya)(eg.
250 mya)
2. Volcanic cones
o pipe-like conduit and vent bringe magma to surface
eruptions range from calm to violent
depends on magma composition
3 Main Types
1. Cinder Cone (kind of material =
Pyroclastic) not really important and not
really big
2. Stratovolcano (composite cone) ( lava +
pyroclastic , felsic to intermediate material )
much bigger
Shield Volcano (lava) mafic material (calm
eruptions)
Magmas
Felsic
Mafic
High viscosity and sticky and high
water content (more than 5%)
Low viscosity and fluid and low
water content less than 1%
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Document Summary

We first need to consider the nature of magma of different. Chemical composition: magma differ in the proportion of elements, results in rocks of different colours, and magmas with different properties. Rock is whiter/pinker -> felsic rock is blacker -> mafic. Read chapter 3 in textbook (pages 72 to 107: do risk analysis and risk management. Volcano zones : constructive (ie. divergent) plate margins, destructive (ie convergent) plate margins, hot spots, most commonly not at plate boundaries (eg. hawaii, both oceanic and continental. Magma: when it comes out of the ground will be in one of the two forms, 1. Fractures (fissures: reaches the surface by coming through either ie. cracks (where a dyke reaches surface) These are calm eruptions: dangers of fissure eruptions. But major eruptions can generate atmospheric effects from so2 gas and co2 gas release (eg. laki eruption in iceland) In particular, enormous flood basalt events may be catastrophic. Linked to mass extinctions (eg, 65 mya)(eg. 2.

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