Ch 3 Volcano  Extrusives

Ch 3 Volcano Extrusives PowerPoint PPT Presentation


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Volcano History . Named after Vulcan - Roman God of Fire and MetalworkingAssociated w/ gods or hell1. Hawaiian - Pele2. Greek

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Ch 3 Volcano Extrusives

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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

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