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Volcanoes

This presentation goes over the basics of volcanoes, how they form, the three different types of volcanoes, and more!
by

Rebecca Miller

on 5 September 2013

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Transcript of Volcanoes

photo credit Nasa / Goddard Space Flight Center / Reto Stöckli
Have you ever wanted to know how volcanoes work?
Volcanoes on Earth
The Cinder Cone, Composite Cone , and Shield Volcanoes
Andesitic Magma
-
has a
thick
velocity
High
gas content
High
silica content
Produces a
Composite volcano
Game on the different kinds of volcanic rocks

http://www.kidsgeo.com/geology-games/rocks-game.php
Game:
L
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a
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n
v
o
l
c
a
n
i
c
R
o
c
k
s
!

Volcanoes don't just happen anywhere, certain patterns occur. Here is a list of volcanically active locations:


The Ring of Fire
, including
both the west coasts of North and South America , the Aleutian Islands, East Asia,
the Philippines, Indonesia, and New Zealand.
A band that stretches from the Mediterranean through Iran
East Asia
Iceland
Hawaii
Windward islands of the Caribbean
Along mid-ocean ridges.
Where do Volcanoes occur?
Volcanic Eruptions
What is a Volcano?
A volcano is vent in the earth's surface in which substances such as

ash
,
gases
, and
magma
erupt.
Some volcanoes erupt, while others simply leak.
The composite volcano
Volcanoes emit:
Gas, Ash, Lava, Dust, and Pyroclastic materials
Gas
- dissolved gases from magma, mainly water vapor, sulfate dioxide, carbon dioxide, and hydrogen sulfate
Ash
- fine particles of rock.
Lava
- Molten basalts and andesites.
Dust
- Extremely fine particles, smaller than ash.
Pyroclastic Materials
- fragments of rock, volcanic glass, and lava. (Size varies)
Viscosity
Silica
Content
Gas
Content
Three factors of magma that affect the type of volcano:
Silica
- Silica

Content

determines viscosity.
Viscosity
- how thick
the magma is; viscosity
determines how magma flows.
Gas
-the percentage
of dissolved gasses.
Different Types of Magmas Determine the type of Volcano.
Ryolitic
-
has
medium
velocity
medium
gas content
medium
silica content
Produces a
cone
Basaltic
-
Runny
velocity
low
gas content
low
silica content
Produces a
shield volcano
What types of volcanoes form at
divergent boundaries
?
Divergent Plate Boundaries
Volcanic Hot Spots
Convergent Plate Boundaries
Molten

rocks
from the mantle rise,break through the crust,and push plates apart at divergent boundaries.
Some
divergent boundaries
occur on land (continental rift valleys),but most occur undersea along mid-ocean ridges.
Undersea-
molten rock passes through the mantle and oceanic crust and erupts through a fissure in a quiet,non-explosive manner.The rising mantle rocks and oceanic crust are basalt,so the lava is basaltic.
Continental-
Magma comes from partially melted mantle(basalt)and continental crust(granites)and erupts non-explosively through a rift.The lava consists of
basalt
and
rhyolite
.
What types of volcanoes form at
convergent boundaries
?
At
convergent boundaries,
one plate sinks under another,the sinking plate partially melts,and the molten rocks rise through the overlying plate.
Oceanic-oceanic convergence-
Magmas consist of molten rock from the mantle and ocean plates themselves and erupt explosively forming volcanic island arcs.The lava tends to be mostly basalt and some andesite.
Oceanic-continental convergence-
Magmas consist of mantle,oceanic crust,and continental crust;erupt explosively;and form composite and cinder cones along the continental margins.The lava tends to be rhyolite and andesite.
Where a plate moves across a rising mantle plume you have a
hot spot
.
In the ocean,
rising molten rock from the deep mantle melt through the ocean crust,erupt non-explosively on the ocean floor,and build up shield volcanoes,which become chains of volcanic islands.
The lava consists of basalt.
The
Hawaiian Islands
are an example of this type of hot spot volcano.
On the continent,
the rising molten rocks must pass through continental crust and erupt non-explosively through fissures.The lava tends to be flood basalt and rhyolite.
The Type of Magma Determines the Type of Volcano.
Thank you for watching! We certainly hope you enjoyed our presentation and that it has increased your knowledge on volcanoes!

This presentation was created by:
Alexis Schwartz and Rebecca Miller
Full transcript