Gel 105 lecture 7 volcanoes 1

Volcanoes: Part Ihttp://www.inquisitr.com/135388/78-million-in-lost-cash-returned-after-japan-tsunami/

Video

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






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


Dehydration


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


different

Varying amounts of SILICA


different


>


different


>

<


different


>

<

Felsic

Mafic

Inter.


different


>

<

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

Gel 105 lecture 7 volcanoes 1

Environment