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 ID: 719132
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8.2 Volcanic Eruptions
Where the rock cycle beginsSlide2
Learning Targets
Compare the types of volcanic eruptions
Describe a method for predicting volcanic eruptionsSlide3
Volcanic Eruption
Magma collects in
magma chamber
Hot magma
expands
creates
pressure
Vent
: crack in the earth’s surface
Magma moving through vent =
eruptionSlide4
How do volcanoes erupt?
Types of eruptions:
Explosive
Non-explosive;
effusiveSlide5
Explosive Eruptions
Can be 1000 times more powerful than atomic bomb
Pressure builds as gases in magma expandSlide6
Explosive Eruptions
Explosion shoots ash and gas high in the air
Heavy debris falls;
light debris may float around for years
Why is ash and gas in the air important?
Blocks sunlight, produces poisonous gas, mixes with water to form acid, global climate changeSlide7
Explosive Eruptions
Some magma crystallizes in the air
Called
pyroclastic material
: ash, lapilli, bomb
Can come down miles from the volcanoSlide8Slide9Slide10Slide11Slide12Slide13Slide14Slide15
Non-explosive eruptions
Another name for non-explosive eruptions
Effusive eruptions
Different mix of
minerals
in magma
No gas build up
Less dangerous but lava flows are consistent and unstoppableSlide16Slide17Slide18Slide19Slide20
Magma Formation
What causes magma to form
High heat
Hot Spots; effusive
Decreased pressure
Divergent boundaries; effusive
Increased water content
Subduction zones; explosiveSlide21
Lava - Viscosity
Viscosity:
Resistance to flow
Honey, ketchup, water
High viscosity
High silica content
Explosive
eruptions
pressure
Low viscosity
Low silica content
Effusive
eruptions
no pressureSlide22Slide23
Lava formations
Explosive
lava
Pyroclastic
material
Pyroclast
– lava solidifies in the atmosphere
Pyroclastic
flow
– fast moving current of superheated gas and rock
Can move hundreds of miles per hour
Effusive
lava
A’a
: jagged, gravelly texture
Pahoehoe
: smooth, even lava flow
Pillow lava: cools underwater forms rounded lobesSlide24Slide25Slide26Slide27Slide28Slide29Slide30Slide31
Predicting Eruptions
History of eruption
Active, dormant, extinct
Earthquakes
Pressure
of magma causes earthquakes
Slope deformation
Plastic deformation due to pressure
Gas emissions
Gas escapes before magmaSlide32
5. Remote Monitoring