Hazards Exam 2
Terms
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- Where do volcanoes form?
- Subduction zones, hot spots, spreading centers, plate edges
- Why are volcanoes that form due to subduction andesitic and not basaltic?
- Water carried with the plate lowers the melting point, so the continent melts as the magma rises, changing it's composition
- What does SiO2 have to do with the type of eruption?
- More SiO2=More explosive
- Viscosity to do with an eruption?
- More=more volatile
- Dissovled gasses to do with an eruption?
- More=more explosive because temp decreases=more solubility
- Where do the most explosive volcanoes form?
- Subduction zones
- What makes volcanoes at subduction zones more explosive?
- Lower melting point=higher SiO2, H2O content, viscosity, and gases
- What three things generate an eruption?
- Low Pressure, temperature rises, water content increases
- 6 types of volcanoes
- Shield, Cinder/Scoria, Composite/Strato, Fissure/Flood, Lava dome, caldera
- 6 types of eruption styles
- Vulcanian, Plinian, crater collapse, icelandic, hawaiian, stromboilian
- Where is crater lake? How did it form?
- Oregon, Mt. Mazma roof collapse
- Volcanoes and eruption styles at spreading centers?
- Fissure, flood. Stromboli and icelandic
- Volcanoes and eruption styles at subduction zones?
- Composite, vulcanian, plinian, caldera
- 3 cascade mountains and the one that has erupted the most in the past 4000 years
- Mt Rainier, Shasta, Lassen Peak; St. Helens
- How do we know the age of eruptions?
- Radiocarbon dating of the surrounding trees
- Describe the eruption of Mt. St. Helens
- Earthquake caused a lahar, which released pressue and caused a lateral pyroclastic flow followed by a plinian eruption
- Why are Shasta and Rainier eruptions so dangerous?
- Lahars, high populations
- Ways a volcano can kill you
- Bombs, pyroclastic flow, lava flow, lahar, acid rain, landslide, gases
- How does a P flow work and why is it so dangerous?
- hot ash/gas/air flowing at high speeds
- What makes a Nuee Ardente different from a pyroclastic flow?
- It glows because it's incandescent
- What causes a mass movement?
- Gravity
- External causes of slope failure
- Material pulls away (tear away) or accumulates (pile up)
- Internal causes of slope failure
-
weak material
water
reduced cohesion
Adverse Geologic Structure - Inherently Weak Material
- Small, book like structure
- Water
- Water fills pores and dissolves rocks or erodes loose material
- Reduced Cohesion
- Rock is compressed, then expands when compressor is lifted.
- Adverse Geologic Structure
-
Ancient slip surfaces
Rock Layer Orientation
Rock Weakness - Mass Movement Triggers
-
Heavy Rain
Earthquakes
Thawing of frozen ground
Construction - Quick Clay
- clay flour+salt from glaciers. Gets lifted above sea level, water removes salt which makes it weak
- Sink hole creation
- Collapse into void, vertical downward movement, move as separate blocks
- Maria
- Sea on the moon
- Why are few impacts visible on Earth?
- erosion
- Comets
- orbit far past outer planets in the Oort Cloud
- Asteroids
- Inner planets/asteroid belt
- Meteroide vs. meteor vs. meteroite
-
-ide=orbiting
-or=in atmosphere
-ite=hit earth - Rate of impact
- 100,000/24 hours
- How are we protected?
- The atmosphere acts like a solid
- Where is meteor crater?
- Arizona
- Evidence for meteor impacts?
- No local volcanoes, steep sides/rim, no sinkholes in area, high temp and pressue minerals found, fused sand
- What is the K/T boundary?
- Crutaceous/Tertiary iridium boundary
- Life after an impact
-
Aftershocks
Wildfires
Acid Rain
Dust
Global Warming
Tsunami - Crater forming process
- Impact, melts, debris, vapor
- Torino Scale
- Rates possible impacts 0-10
- Icelandic
- Non-explosive, basalt, shield
- Hawaiian
- Non explosive, basalt, shield
- Strombolian
- Low explosions, basalt to slight andesite, scoria/cinder
- Vulcanian
- Moderately explosive, basalt to rhyolite, scoria and strato
- Plinian
- Highly explosive, andesite to rhyolite, strato
- Caldera
- high viscosity, high volit, large volume
- Shield/Flood Basalts
- Low viscosity, low volatiles, large volume
- Scoria
- Low/med viscosity, med/high volatiles, small volume
- Strato
- med/high visco, med/high vol, large volume
- Lava Dome
- high visco, low vol, small volume
- Creep
- Slow and dry
- Falls
- Fast and dry
- Transitional Slide
- rapid and moist
- Rotational Slide
- slow and moist
- Mudflow
- Rapid and saturated
- Snow avalanche
- Rapid and moist
- Subsidence
- Rapid and moist
- Debris flow
- Rapid and saturated