Volcanoes

Definitions:

Volcano –

Hot Spot –

A mountain that forms when lava, ash, rocks, and melted rock material piles up and hardens. Eruptions may be violent or “peaceful”.

A location of abnormal amounts of heat in the mantle. The heat/pressure forces magma up through the crust. As a plate moves over top, a row of volcanoes are formed.

– E.g. - Hawaii

Facts:

Volcanoes can be found on land or on the ocean floor.

They are common along plate boundaries.

Volcanoes erupt differently mainly due to the viscosity of the magma. The more viscous the magma, the more violent the eruption. E.g. – Molasses is more viscous than water.

Drawings: (2 ways volcanoes are made)

Hot Spot Subduction Zone

3 ways to classify:

Active –

Dormant –

Extinct –

are erupting or have recently erupted

have not erupted for a long time but show signs of underground activity

have not erupted for a long time and show no signs of underground activity

3 types of volcanoes:

Shield Gently sloped sides, lava hardens to form

wide base Erupts with little force Made mostly of basalt

Interesting Fact:

The 2 types of lava are Aa and Pahoehoe

Aa

Aa

Aa

Pahoehoe

Pahoehoe

Pahoehoe

3 types of volcanoes (cont.):

Cinder Cone Steep sides Erupts with tremendous force

E.g. – Krakatau Indonesia - 1883 could be felt in London and Australia

3 types of volcanoes (cont.):

Composite Cone Alternating layers of rock, lava, and ash Erupts with either tremendous force or

little force E.g. – Mt. Saint Helens

Washington - May 18, 1980 60 people were killed

VEI Description Plume Height Volume Classification How often Example

0 non-explosive < 100 m 1000s m3 Hawaiian daily Kilauea

1 gentle 100-1000 m 10,000s m3 Haw/Strombolian daily Stromboli

2 explosive 1-5 km 1,000,000s m3 Strom/Vulcanian weekly Galeras, 1992

3 severe 3-15 km 10,000,000s m3 Vulcanian yearly Ruiz, 1985

4 cataclysmic 10-25 km100,000,000s

m3Vulc/Plinian 10's of years Galunggung, 1982

5 paroxysmal >25 km 1 km3 Plinian 100's of years St. Helens, 1980

6 colossal >25 km 10s km3Plin/Ultra-

Plinian100's of years Krakatau, 1883

7 super-colossal >25 km 100s km3 Ultra-Plinian 1000's of years Tambora, 1815

8 mega-colossal >25 km 1,000s km3 Ultra-Plinian10,000's of

yearsYellowstone, 2

Ma