Ch 3 Volcano & Extrusives

1. Ch 3 Volcano & Extrusives

2. Volcano History • 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 • 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 • 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 • 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 • 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 • (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