Volcanoes 1

Volcano definition

where magma and gas leak out from earths crust and mantle

Magma vs lava

magma is under the surface, lava is magma that comes out of surface

magma extrudes as __ or explodes as

lava, pyroclastic material

Extrusives:

• quick cooling

• tiny crystals

• lava and ash

Intrusives:

• slow cooling

• large crystales

• “ingenious intrusion”

Storage Region

• bottom region

• deep and hot

• periodite (mantle) melts to magma

Transport magma

• 2nd to bottom

• 2 types of magma pathways

• dikes and sills

• between source region and magma chamber

Storage region

• magma chamber @ the crust

Eruption Region

• surface volcanoes

Magma properties

• DENSITY: 2.5-3.3 g/cm3

• more dense than water, less dense than mantle

• approx same density as crust

• TEMP: 600-1200

Extrusive Rock Type

1) Basalt

2) Andesite

3) Dacite

4) Rhyolite

BADR

What is the most mafic rock?

basalt (f or m)

what is the most felsic rock?

rhyolite (f or m)

Which rock has less silica?

basalt Si content

Which rock has more silica

rhyolite Si content

Which rock is darker?

basalt (dark or light)

which rock is lighter?

rhyolite (dark or light)

which rock has low viscosity?

basalt viscosity

which rock has high viscosity?

rhyolite viscosity

if its effusive, there is

• low visocsity

• non explosive (like magma)

• low gas content and volatiles

• low crystallization

• hot (1200-1400)

if its explosive, there is

• high viscosity

• explosive (ask

• high gas content and volatiles

• high crystallization

• cool (600-1000)

magma viscosity

10-10 to the power of 15 (Pa s)

• depends on temp, gas content, crystal content

what controls flow and eruption style?

magma viscosity

Felsic ingeneous rocks have

• 65-75 SiO2

• light color

• rich in K, NA, Al, Si

• high viscosity/ sticky

• granite and rhyolite

Mafic Ingenous rocks have

• 45-55 SiO2

• dark color

• rich in Mg, Fe

• low viscosity/ runny

• basalt, Gabbro

Magma average temp

600-1200 •celcius

hot magma is

low viscosity, low silica (mafic)

cool magma is

high viscosity, high silica (felsic)

Magma gas content (volatiles)

• H20

• CO2

• SO2

Felsic and mafic have what percent dissolved volatiles

• felsic 4-6 %

• magic 0.1-1 %

As magma rises the amount of bubbles__

increases

• magma rises

• lower PSI

• less solubility

• leads to bubbles

What is the most important factor that determines ingenous texture/ grain size?

cooling rate

2 types of flowy lava

Pahoehoe and Aa

What is the similarity and difference of Pahoehoe and Aa

• same composition (basalt)

• flow differently

• AA: crumbly

• PAHOEHOE: flowy

Is high associated with Mafic or Felsic?

Felsic (explosivity)