VolcanoesVolcanoes

March 2012March 2012

Eruption TypesEruption Types

• 1. Explosive • ejects gases, ash, and pyroclastics shot into air and across ground

• caused by lots of water and gases trapped in magma

Eruption TypesEruption Types

• 2. Nonexplosive • lava runs down the slopes of the volcano

Forming VolcanoesForming Volcanoes

1. Subduction Zone -most volcanoes formed this way

(plate boundary)

-one plate melts as it goes under the other, magma rises upward

• http://www.classzone.com/books/earth_science/terc/content/visualizations/es0902/es0902page01.cfm?chapter_no=visualization

Forming VolcanoesForming Volcanoes

2. Hot Spots -located in middle of plates, not boundary

-very thin crust allows magma to rise up, volcano forms, crust moves, starts over

• http://www.wwnorton.com/college/geo/egeo2/content/animations/2_6.htm

Types of VolcanoesTypes of Volcanoes

1. Shield Volcano • Nonexplosive eruptions– Layer upon layer of hardened

lava

• Gradual sloping sides, but can be enormous in size

Mt Etna and Mauna KeaMt Etna and Mauna Kea

Mt. Etna in Italy-notice how broad it is; this volcano is south of Vesuvius on the island of Sicily

Mauna Loa-part of Mauna Kea, which is the largest mountain on Earth when measured from the ocean floor

Types of VolcanoesTypes of Volcanoes

2. Cinder Cone Volcano • explosive eruptions– Layer upon layer of

pyroclastics

• Erode quickly because they are not “glued” together by lava

Paricutin-MexicoParicutin-Mexico

Paricutin erupting at night. The volcano ejected materials from a hole in a cornfield until it covered a whole town. The tower from this church is all that is left of town.

Types of VolcanoesTypes of Volcanoes

3. Composite Volcano

(aka: Statro volcano)

• Made from explosive and non-explosive eruptions

• Alternating layers of lava and pyroclastics

StratovolcanoesStratovolcanoes

Mt. St. Helens, May 18, 1980

Mt Vesuvius, Italy- notice all of the buildings and people that surround the volcano.

Predicting EruptionsPredicting Eruptions

• Volcanologists look for:

1. Faults – the Earth cracks when pressure builds up

2. Gases – content and amount of gases

3. Rockfall (RF) – landslides/deformation

4. Volcano Tectonics (VT) – earthquakes in volcano

Volcanoes and Global CoolingVolcanoes and Global Cooling• Explosive eruptions have released enough

gases and ash into the atmosphere to effect weather globally by blocking the sun’s heat

Picture TimePicture Time

This is some of the damage from Mt. St. Helens in May of 1980. That is volcanic ash on the right, not snow.

Iceland, HeimaeyIceland, Heimaey

The people of Iceland live in very close proximity to many volcanoes.

Iceland-Cold with VolcanoesIceland-Cold with Volcanoes

Volcanoes UNDER the glaciers melt the ice and make glacial lakes.

This is a cinder cone volcano; it just happens to be quiet and snowy for the moment.

Surtsey, IcelandSurtsey, Iceland

Surtsey appeared off the coast of Iceland in 1963. In four years, the island was 1 sq. mile and had elevations of 560 feet!

Mt. Etna, ItalyMt. Etna, Italy

This is just a really cool picture of lava from Mt. Etna.

Pacific Ring of FirePacific Ring of Fire

Pacific Hot SpotsPacific Hot Spots