1. Ch 3 Volcano & Extrusives

2. Volcano History 1. Hawaiian - Pele
Named after Vulcan - Roman God of Fire and Metalworking
Associated w/ gods or hell
1. Hawaiian - Pele
2. Greek – Hephaestus; son of Hera
3. Europe in the middle ages -
a. Gateway to hell
b. Prisons of the damned;
Noises were "screams of
tormented souls“

3. Volcano Distribution 2 major volcano belts Pacific Ring of Fire
Mediterranean Belt

4. Magma vs. Lava Magma – liquid rock under the surface
Lava – magma that reached the surface
Magma described as Mafic, Felsic, or Intermediate

5. Mafic Magma Less than 50% silicate high magnesium, iron, and calcium
Ex minerals: olivine, pyroxene, amphibole, biotite mica, and plagioclase feldspar.
Ex rocks: basalt and gabbro.
high magnesium, iron, and calcium
dark color
Dense
quiet eruptions
low viscosity

6. Felsic Magma 65% silicates low in Mg, Fe, & Ca light color less dense
Ex minerals: quartz, muscovite mica, and orthoclase feldspar
Ex rock: granite
light color
less dense
high viscosity
explosive eruptions

7. Speed of Lava Flow Based on 3 traits Temperature Amount of Silicates
Hotter is faster, cooler is slower
Amount of Silicates
Low is faster, high is slower
Amount of dissolved gases
High is faster, low is slower

8. 3 Types of Volcanoes Shield Volcano mafic magma; basalt
Common above hot spots
Hawaiian Islands – Mauna Loa
Large but not steep
Nonviolent and quiet oozes;
low viscosity, runny

9. 2 Types of Low Flow AA Pahoehoe surface cools while flowing
Looks broken
Pahoehoe
Surface stays fluid, keeps flowing
Looks smooth and ropy

10. 2. Cinder Cone Felsic magma; explosive Small but steep; 33°
Build up of cinders (pumice, scoria, pyroclastics, or tephra)
Tend to pop up next to other volcanoes

11. 3. Stratovolcano Intermediate, mafic & felsic large (1 - 10 km across)
Ka-boom then ooze
Explosive
Adnesite rock (intermediate) – higher silica content
Sticky magma that plugs up til breaking pt. (Zits on earth)
Creates pyroclastic material
Ex. Cascade Range, Dante’s Peak, Mt. Fiji 

12. What comes out?
Pyroclastics – different sizes of “fire broken” rock; cool fast
Ash (tuff): smallest
Pumice: volcanic glass; gas bubbles
Scoria: cinder, basalt, iron rich; gas bubbles
Lapilli (walnut-sized)
Volcanic bombs (basalt)

13. More Dangers Pyroclastic flows Gases Lahars
(nuée ardente) – hot & fast
Gases
CO2
SO2 + water = sulfuric acid
Lahars
Down hill mud flow
Snow & ice melt
Picks up debris
Local dangers

14. Other Volcanic “Things”
Mafic Flows –
Lava tubes
Pillow basalt
Columnar Jointing
Fountains

15. Lava Domes – super volcanoes
all felsic
high silicate
high viscosicty
very violent
Obsidian – cools instantaneously; Newberry Crater Obsidian flows
Caldera
Yellowstone National Park

16. Calderas Volcanic peak disappears Major explosion
Leaking magma to side
Collapse into magma chamber

17. Lava plateaus Broad flat-lying plains Stacked layers of flood basalts
basalt flows extruded from linear fissures
ex: Columbia Plateau
Will see columnar jointing

18. Historical Eruptions 5000 BC, Mt. Mazama, Oregon
40 km3 volcanic debris
Crater Lake
79 AD Vesuvius and Pompeii
Historic remains
1815 Mt. Tambora, Indonesia
30 km3 volcanic debris
"year without a summer
1883 Krakatoa, Indonesia
18 km3 volcanic debris
Heard round the world
1902 Mt. Pelee, Martinique (Carribbean)
nuee ardente killed 28,000 instantly
May 18, 1980 Mt. St. Helens, Washington State
1 - 2 km3 volcanic debris
June 15, 1991 Mt. Pinatubo, Philippines
2m2 of dust & fine ash
SO2 aerosol cloud circled Earth in just 21 days
stratospheric haze caused a 1 degree temperature drop

19. Vesuvius and Pompeii