Let’s Learn More About Pompeii
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D. Types of Eruptions
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Quiet Eruptions
Happen if magma is thin,
runny, & flows easily
Occur in Hawaii and Iceland
Produce pahoehoe and aa
Low Silica
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Explosive Eruptions
Happen if magma is thick &
sticky
Gasses (pressure) build up
within thick magma
Cause very forceful
eruptions
High Silica
On May 18, 1980, at 8:32 a.m.
Pacific Daylight Time, a
magnitude 5.1 earthquake shook
Mount St. Helens. The bulge and
surrounding area slid away in a
gigantic rockslide and debris
avalanche, releasing pressure,
and triggering a major pumice
and ash eruption of the volcano.
Thirteen-hundred feet (400
meters) of the peak collapsed or
blew outwards. As a result, 24
square miles (62 square
kilometers) of valley was filled by
a debris avalanche, 250 square
miles (650 square kilometers) of
recreation, timber, and private
lands were damaged by a lateral
blast, and an estimated 200
million cubic yards (150 million
cubic meters) of material was
deposited directly by lahars
(volcanic mudflows) into the river
channels. Fifty-seven people
were killed or are still missing.
USGS Photograph taken on May
18, 1980, by Austin Post.
Different Eruptions Result In…
DIFFERENT VOLCANIC LANDFORMS
E. Landforms from Lava and Ash
1.
Shield Volcanoes
a.
Form by thin layers of lava that pour out of a vent and harden on previously
formed layers
Ex. Mauna Loa, Hawaiian Islands
E. Landforms from Lava and Ash
1.
Shield Volcanoes
a.
Form by thin layers of lava that pour out of a vent and harden on previously
formed layers
Ex. Mauna Loa, Hawaiian Islands
2.
Cinder Cone Volcanoes
a.
b.
Form by ash, cinders, and bombs that erupt from thick and stiff lava.
Material piles up in a cone-shaped pile
Ex. Paricutin, Mexico (shown in Intro Video)
E. Landforms from Lava and Ash
1. Shield Volcanoes
a.
Form by thin layers of lava that pour out of a vent and harden on previously
formed layers
Ex. Mauna Loa, Hawaiian Islands
2. Cinder Cone Volcanoes
a.
b.
Form by ash, cinders, and bombs that erupt from thick and stiff lava.
Material piles up in a cone-shaped pile
Ex. Paricutin, Mexico (shown in Intro Video)
3. Composite Volcanoes (think “combo”)
a.
b.
Erupt both lava and ash
Volcano slopes’ are cone-shaped and its layers alternate from lava layers to
ash layers
Ex. Mt. Fuji, Japan & Mt. St. Helen’s, Washington
E. Landforms from Lava and Ash
1.
Shield Volcanoes
a.
Form by thin layers of lava that pour out of a vent and harden on previously
formed layers
Ex. Mauna Loa, Hawaiian Islands
2.
Cinder Cone Volcanoes
a.
b.
Form by ash, cinders, and bombs that erupt from thick and stiff lava.
Material piles up in a cone-shaped pile
Ex. Paricutin, Mexico (shown in Intro Video)
3.
Composite Volcanoes (think “combo”)
a.
b.
Erupt both lava and ash
Volcano slopes’ are cone-shaped and its layers alternate from lava layers to
ash layers
Ex. Mt. Fuji, Japan & Mt. St. Helen’s, Washington
4.
Caldera
a.
b.
When huge eruptions occur, they can sometimes empty the main vent AND
magma chamber.
The mountain looks like a hollow shell as the top of the mountain collapses
inward.
Ex. Crater Lake, Oregon
HOMEWORK DUE: THURSDAY 1-26-12
• Read Textbook pages 187-188
• Answer Section 2 Review Question #’s 2 and 4
• Continue to work on your Volcano Brochure