Volcano Notes - Mrs. Weisenbach's Biology Cabinmrsweisenbachsra.weebly.com/uploads/3/7/2/4/37242969/... · 2019-12-10 · Volcano Notes . 2 Individual Volcanoes - Locations ! Subduction

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Volcano Notes

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Individual Volcanoes - Locations

n  Subduction Zones: •  Association between volcanoes & subduction

zones. •  Ring of Fire = Ring of Subduction Zones

n  Continental Rift Zone: •  A few volcanoes are associated with rift zones.

n  Hot Spots: •  Some coincide with plate boundaries, most

don’t. •  e.g. Hawaii

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Where are volcanoes located? Is there a pattern?

AT PLATE BOUNDARIES

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Ring of Fire

There are currently about 1500 active volcanoes around the world

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Volcanoes n  Not currently erupting (but still could anytime)

•  Dormant (still has seismic activity and lava flow)

n  Currently erupting

•  Active

n  Not able to erupt (permanently) •  Extinct (no seismic activity, no magma flow)

Volcano Structure

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Volcanoes

n  Where do volcanoes occur? • Along plate boundaries and above hot

spots • A hot part in the middle of the mantle

that melts rock that is then forced upward as magma

• Hotspot

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Magma!

What is the difference between “lava” and “magma”? Magma is below ground and lava is above ground.

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Volcanoes

n  Shield Volcano: A broad volcano with gently sloping sides, quiet eruptions, silica-poor lava. (ex. Hawaiian Islands)

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Volcanoes

n  Cinder Cone Volcano: steep sided volcano, explosive eruptions that throw lava and rock in the air, silica-rich lava (ex. Paricutin in Mexico)

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Volcanoes

n  Composite Volcano: a small volcano, both quiet and violent eruptions

n  (ex. Mt. St. Helens) n  Also called “stratocones”

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n  Pyroclastic flow n  Lahars/Mud flows n  Pyroclastic fall n  Lava flow n  Noxious Gas n  Earthquakes

Volcanic Hazards

Courtesy of www.swisseduc.ch

Pyroclastic Flow

n  For example, eruption of Vesuvius in 79 AD destroyed the city of Pompeii

Pompeii (79AD)

On August 24, 79AD Mount Vesuvius literally blew its top, erupting tonnes of molten ash, pumice and sulfuric gas miles into the atmosphere. Pyroclastic flows flowed over the city of Pompeii and surrounding areas.

Pompeii (79AD)

Pyroclastic flows of poisonous gas and hot volcanic debris engulfed the cities of Pompeii, Herculaneum and Stabiae suffocating the inhabitants and burying the buildings.

Vesuvius today

n  Vesuvius remains a hazardous volcano with heavily populated flanks: •  around 1.5 million

people live in the city of Naples alone

•  Naples is situated approx. 30 km from Vesuvius

•  Pyroclastic flows can flow up to 100 km from source!

Bay of Naples

Vesuvius

Naples

Courtesy of www.swisseduc.ch

What is pyroclastic flow?

n  Dense, destructive mixture of volcanic ash, rock and gas travelling at high speeds.

n  Usually travels down hill

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Lahars n  Hot volcanic activity can melt

snow and ice n  Water picks up rock and

debris n  Forms fast flowing, high

energy torrents n  Destroys all in its path