8.2 volcanic eruptions
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8.2 Volcanic Eruptions. Where the rock cycle begins. Learning Targets. Compare the types of volcanic eruptions Describe a method for predicting volcanic eruptions. Volcanic Eruption. Magma collects in magma chamber Hot magma expands creates pressure - PowerPoint PPT PresentationTRANSCRIPT
8.2 VOLCANIC ERUPTIONS
Where the rock cycle begins
Learning Targets
1. Compare the types of volcanic eruptions
2. Describe a method for predicting volcanic eruptions
Volcanic Eruption1. Magma collects in magma chamber2. Hot magma expands creates
pressure3.Vent: crack in the earth’s surface4. Magma moving through vent =
eruption
How do volcanoes erupt?1. Types of eruptions:
a)Explosiveb) Non-explosive; effusive
Explosive Eruptions1. Can be 1000 times more
powerful than atomic bomb
2. Pressure builds as gases in magma expand
Explosive Eruptions1. Explosion shoots ash and gas
high in the air2. Heavy debris falls; light debris
may float around for years3. Why is ash and gas in the air
important?a) Blocks sunlight, produces poisonous
gas, mixes with water to form acid, global climate change
Explosive Eruptions1. Some magma crystallizes in the
air2. Called pyroclastic material:
ash, lapilli, bomb
3. Can come down miles from the volcano
Non-explosive eruptions1. Another name for non-explosive
eruptionsa)Effusive eruptions
2. Different mix of minerals in magma
3.No gas build up4. Less dangerous but lava flows
are consistent and unstoppable
Magma Formation1. What causes magma to form
a) High heati. Hot Spots; effusive
b) Decreased pressurei. Divergent boundaries; effusive
c) Increased water contenti. Subduction zones; explosive
Lava - Viscosity1. Viscosity: Resistance to flow
a) Honey, ketchup, water2. High viscosity
a) High silica contentb)Explosive eruptions pressure
3. Low viscositya) Low silica contentb)Effusive eruptions no
pressure
Lava formations1.Explosive lava Pyroclastic
materiala) Pyroclast – lava solidifies in the
atmosphereb)Pyroclastic flow – fast moving
current of superheated gas and rocki. Can move hundreds of miles per hour
2.Effusive lavaa) A’a: jagged, gravelly textureb) Pahoehoe: smooth, even lava flowc) Pillow lava: cools underwater forms rounded
lobes
Predicting Eruptions1.History of eruption
a)Active, dormant, extinct2.Earthquakes
a)Pressure of magma causes earthquakes
3.Slope deformationa) Plastic deformation due to pressure
4.Gas emissionsa) Gas escapes before magma
5. Remote Monitoring