8th grade Earth Science

Volcanoes

Shield

Composite

Cindercone

There are three types of volcanoes:

Formed by layer after layer of lava.

Usually have low silica content, and gases can escape easily.

Has quiet eruptions.

Extremely broad and flat in shape.

Found in Hawaii.

SHIELD VOLCANOES

Shield volcanoes have gently sloping sides that can stretch for miles.

These pictures are Mauna Loa, a volcano on the Big Island of Hawaii.

SHIELD VOLCANOES

A typical Hawaiian Eruption

Can sometimes be called Stratovolcanoes.

Formed by alternating layers of lava flow and cinders or ash.

Has a high silica content and gases are usually trapped.

Has explosive eruptions.

Mount St. Helens and Mount Rainier in Washington.

COMPOSITE VOLCANOES

• Mt. Mayon, Phillippines (left)• Arenal, Costa Rica

(below)• Mt. Rainier, Washington (bottom, left)

COMPOSITE VOLCANOES

1980 2000

Mount St. Helens ( COMPOSITE)

Eruption of Mt. St. HelensVIDEO

Virtual Tour of Mt. St. Helens

Harry Truman – the man who refused to leave “his” mountain.

Mt. St. Helens (COMPOSITE)

Formed by layers of cinders and ash, not a lot of lava erupts from these volcanoes.

Very explosive when it erupts.

Has trapped gases.

The shape is nearly perfect on all sides… almost like an orange road pylon.

CINDERCONE VOLCANOES

CINDER CONE VOLCANOES

This eruptions that created Paricutin began in 1943 and continued to 1952. Most of the explosive activity was during the first year of the eruption when the cone grew to 1,100 feet (336 m). The cone continued to grow for another 8 years but added only another 200 feet.

Psricutin, Mexico (CINDERCONE)

In mythology, Etna was identified as the location of the forge of Volcan, home of the Cyclopses, and where the giant Enceladus laid (eruptions being his breath and earthquakes being his motion). Etna’s beauty, frequent eruptions, and long record of eruptions makes it one of the world’s best know volcanoes.

Mt. Etna, Italy (COMPOSITE)

City of Pompeii, Mt. Vesuvius(COMPOSITE)

Images of Pompeii

Both pictures are the remaining core of the volcanic neck of a once active volcano.

Located in Wyoming (left)Ship Rock, San Juan County New Mexico (below)

Devils Tower/Ship Rock

Mt. St. Helens has been periodically erupting for the 2 years. It is building its peak back up --- slowly but surely.

Latest Eruptions

Montserrat Volcano in the Caribbean. A large explosion and dome collapse occurred on March 3, 2004, causing a high eruption column and basal surge.

Latest Eruptions

Latest Eruptions

Etna Volcano in Sicily

Late October, 2002

Lava – molten rock that oozes out of volcanoes.

TephraAsh – smallest sized tephra

Cinders – small pieces of cooled lava up to the size of a basketball.

Bombs – any projectile bigger than a basketball.

Materials thrown out of a volcano

Volcanic ash can cover areas like a snow storm

ASH – the smallest size tephra

Lava Ash

Lava Cinders

Bombs – cinders usually come out in a pyroclastic flow

Lava Bombs

Aa – Thick, chunky and difficult flow

Pahoehoe – Thin, watery, and easily flows

Types of lava

Lava Flows

Dante’s Peak Eruption…video