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Volcanoes
Chapter 8Section 2
Class Outcomes
Describe a volcanoName and describe the 4 types of volcanoesDifferentiate between Pahoehoe and Aa lava
Volcano
Area where magma and gases are released to the Earth’s surface.Area where magma becomes lava
Magma = under surfaceLava= above surface
Have circular shaped openings called cratersRelease Tephra, or solid lava, that enters the air during an eruption.
Subduction Zone VolcanoesOceanic plate dives under and melts. The newly formed magma rises to the surface and creates a volcano.
4 types of volcanoes
Shield VolcanoesCinder Cone VolcanoesComposite VolcanoesFissure Eruptions
Shield Volcanoes
Made from basaltic lava Thin and easy flowing“pahoehoe”
Gradually sloping sidesBroad/ largest volcanoes on earthHawaiian Islands/Iceland
Mauna Loa
Cinder Cone Volcanoes
Short in height (less than 300m)Made of tephraViolent eruptions from gas buildup
Lava and gas shoot high in the air and cool to form volcano
Short eruption time
Composite Volcanoes
Steep sided mountainComposed of alternating layers of basaltic lava and tephraExplosive eruptions followed by lava flowsMt. St. Helens, Mt. Ranier, Mt. Shasta
Composite = pyroclastic flows
Hot gases and ashes released at the beginning of a composite eruption2000 degrees FahrenheitUp to 450 miles/hourDeadliest event of a composite eruption
Pyroclastic Flow
Composite = “Lahars”
Mud Flows caused by the super heating of glaciers on the top of these high mountains.Water + Ash = Lahar2nd deadliest aspect of these giants.
Mt. Shasta, California
Fissure Eruptions
Basaltic lava flows from cracks in the earth’s crust
Thin and flows easily
Form flat landforms known as lava plateaus/flood basalts.
Volcano Tour on Google Earth
tour
Fissure Eruption, Kilauea Volcano field, Hawaii
“Pahoehoe vs. Aa”
Pahoehoe lavaThin and flows easily
Aa lavaThick and chunky and doesn’t flow, but breaks apart as it moves.
?Aa
?Pahoehoe
What kind of volcano would be the best to have in your backyard?
Extinct• Have no magma chamber or source.
Active• Have regular, predictable eruptions that never
gain strength.
Dormant • Have irregular, unpredictable eruptions and can
be very catastrophic in strength.
Enjoy the Show
Mountains of Fire