8. Volcanoes Flashcards
1
Q
What is magma temperature? What role does it play in how volcanoes melt?
A
- the temperature of the magma
- informs how viscous the magma will be
- determined by the silica content
- basalt has higher temperature, intermediate moderate, felsic low temperature
2
Q
What is Silica?
A
- compound in rocks and melts at molecular unit
- tetrahedral structure that polymerizes together to form stiff framework
- higher the amount of silica, more viscous/ stiff and lower the melting point
3
Q
What is rhyolite?
A
- a felsic volcanic rock
- has >60% silica
- more viscous and stiff, lower temperature
- in calderas and composite/ stratavolcanoes
- chemical equivalent to granite
4
Q
What is Andesite?
A
- an intermediate volcanic rock
- intermediate in temperature and viscosity
- porphyritic in texture- has large crystals with fine grained texture
5
Q
What is basalt?
A
- a mafic volcanic rock
- 45-50% silica
- high melting point, low in viscosity
- found in ocanic crust and in shield volcanoes
6
Q
What is advection?
A
The flow of heat by a liquid
7
Q
What 4 types of volcanoes are there?
A
- Composite/ stratavolcanoes
- Shield volcanoes
- Calderas
- Flood volcanoes
8
Q
Describe composite/ stratavolcanoes.
A
- intermediate and felsic
- low melting temperature, high in viscosity
- steep sides
- explode- felsic and intermediate have the tendency to stay at depths and build up pressure
9
Q
Describe shield volcanoes and their lava.
A
- lava high in CO2, H20, SO2
- basalt (mafic), low viscosity and silica
- some explosions
- In Hawaii, areas that have rifted
10
Q
Describe Flood Basalts.
A
- thick basalt lava flows
- forms columnar jointing
- fissure eruption- a line of volcanic eruption
11
Q
Describe calderas.
A
- intermediate and felsic
- massive collapsed dome
- super volcano
- magma beneath crust collapsed and landed on top of it
12
Q
What is a tephra?
A
when ash falls and it becomes rock
13
Q
What are the two factors that contribute to the explosive nature of volcanoes?
A
- Magma composition- tell us eruptive power/ how viscous
2. Dissolved volatiles- cause magmas to explode on surface
14
Q
What are the 3 types of magma composition? Match them with the volcanic rocks.
A
- Felsic– rhyolite
- Intermediate– andesite
- Mafic– basalt
15
Q
Describe felsic volcanic rock.
A
- rhyolite
- high viscosity
- in composite and calderas volcanoes
- > 60% silica–> stiff, rise slowly and builds up pressure
- sometimes explodes
- have more volatiles
- melt at lower temperature
