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