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Volcanoes: Part Ihttp://www.inquisitr.com/135388/78-million-in-lost-cash-returned-after-japan-tsunami/
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Learning Objectives1. Know the different types of volcanoes
and their associated features2. Understand volcanoes’ relationship
with to plate tectonics3. Know what geographic regions are at
risk from volcanoes4. Know the effects of volcanoes and
how they are linked to other natural disasters
http://bali-news-views.blogspot.com/2010/10/mentawai-tsunami-destroys-179-houses.html
Magma =
http://bali-news-views.blogspot.com/2010/10/mentawai-tsunami-destroys-179-houses.html
*Both terms for liquid rock*
Lava= On Earth’s surface
Magma =
http://bali-news-views.blogspot.com/2010/10/mentawai-tsunami-destroys-179-houses.htmlLava= On Earth’s surface
Magma = Within Earth
http://bali-news-views.blogspot.com/2010/10/mentawai-tsunami-destroys-179-houses.htmlLava= On Earth’s surface
Magma = Within Earth
http://bali-news-views.blogspot.com/2010/10/mentawai-tsunami-destroys-179-houses.htmlLava= On Earth’s surface
Magma = Within Earth
http://bali-news-views.blogspot.com/2010/10/mentawai-tsunami-destroys-179-houses.htmlLava= On Earth’s surface
Where do you find volcanoes?
Hot spots
2/3s in “Ring of Fire”
How magma forms
How magma forms Which parts liquid/molten?
How magma forms
Outer core
Which parts liquid/molten?
Why?
How magma forms Which parts notliquid/molten?
Inner core?
Why?
How magma forms Which parts notliquid/molten?
Inner core?
Too much pressure!
Why?
Question: How does magma
form?
Answer:
Heat + Pressure
To melt a rock…
To melt a rock…
1) Increase heat
To melt a rock…
2) Decrease pressure
To melt a rock…
2) Decrease pressure
This one first!
Pressure: Where???
Pressure: Where???
Pressure: Where???
Sea-Floor Spreading
Sea-Floor Spreading
Lighter here
Hot Spots/PlumesSuperheated rock rises, melts
Hot Spots/PlumesSuperheated rock rises, melts
Re
du
cin
g p
ress
ure
Return to Heat in moment…
Return to Heat in moment…THIRD WAY!
Add water!
From where?
Water saturated down-going plate
Dehydration
Water saturated down-going plate
Dehydration
Water saturated down-going plate
Melting induced!
Melting
*Subduction Zones*
Dehydration
Melting
Back to heat…
Hot magma melts crust
Hot magma melts crust**Very important**
Hot magma melts crust
Continental & oceanic crust =
different
Continental & oceanic crust =
different
Varying amounts of SILICA
Continental & oceanic crust =
different
Varying amounts of SILICA
>
Continental & oceanic crust =
different
Varying amounts of SILICA
>
<
Continental & oceanic crust =
different
Varying amounts of SILICA
>
<
Felsic
Mafic
Inter.
Continental & oceanic crust =
different
Varying amounts of SILICA
>
<
Continent
Ocean
Felsic
Mafic
Inter.
Why?
Silica-rich crystalize last—melt first!
Silica-rich crystalize last—melt first!
Granite
Where do you find them? Why?
Granite
How does oceanic crust produce granite?
Granite
Partial melting: Mostly Si-rich minerals
Partial melting: Mostly Si-rich minerals
Water reduces melting temp
H2O
Cool, but so what?
>
<
>
<
Thought Experiment:Imagine blowing bubble in peanut butter
>
<
BANG!
FLOW
>
<
BANG!
FLOW
Volatile: Water, CO2, etc. = EXPLOSION!
>
<
BANG!
FLOW
Volatile: Water, CO2, etc. = EXPLOSION!
Hot magma melts crust**Very important**
Important why?
Hot magma melts crust*Incorporates Si-rich rocks*
>Viscosity
A
B BA+B
Extending that idea… We get:
Viscosity makesvolcanoes
The less viscous, the further it can flow before hardening
The less viscous, the further it can flow before hardening
Low viscosity and broad (basaltic)
Low viscosity and broad (basaltic)
Example: Hawaiian Islands
Video
Very high viscosity; round & smallish
Example: Mono Crators (CA)
Very high viscosity; round & smallish
Potentially VERY explosive
Form within collapsed calderas
Mixed/alternating comp.; explodes & flows
Example: Mt. St. Helens
Mixed/alternating comp.; explodes & flows
Example: Mt. St. Helens
“Classic” volcanoes
Cinder Cone
• Built around vents/faults/sides of volcanoes
• Composed of ‘scoria’/lava rock• Various compositions
Cinder Cone
• Built around vents/faults/sides of volcanoes
• Composed of ‘scoria’/lava rock• Various compositions
Volcán de Parícutin
Video
Pyroclastic: ‘fire’ + ‘broken’
• Ash, scoria, lapilli/blocks/bombs, etc. ejected from volcano
• Huge potential for damage
• Champagne analogy Scoria/cinder
