Transcript Three Types of Volcanoes

Three Types of
Volcanoes
VOLCANOES
EQ: What are the types of
volcanoes and how are they
formed?
So, What Is a
Volcano?
•A volcano is a weak spot in the
crust where molten material, or
magma, comes to the surface.
The Ring of Fire
Subduction zones
The Ring of
Fire is a
volcano
belt
formed by
many
volcanoes
that
border the
Pacific
Ocean.
How are
volcanoes
formed?
Deep in the earth it is very
hot and rocks melt.
The melted rock is
called magma and is
lighter than the rocks
around it so it rises.
Sometimes it finds a
crack or hole in the
earth’s crust and bursts
through it (vent). This
is how a volcano begins.
Why do
volcanoes
erupt?
Pressure builds deep in the earth
where the magma is. Suddenly
the gases escape and violently
explode.
What are the
different
kinds of
volcanoes?
Classifying Volcanoes

Composite or
Strato
• Active
• Cinder
Cone
• Intermittent
• Shield
• Dormant
• Extinct
VOLCANIC ACTIVITY
ACTIVE - A volcano that has erupted in the
recent past and is expected to erupt again.
INTERMITTENT – A volcano that erupts in
fairly regular time periods.
DORMANT - A “sleeping” volcano. A volcano
that has not erupted in the recent past, but could
erupt again.
EXTINCT - A volcano that is not expected to
erupt again.
Shield Volcanoes

A shield volcano is a
large, gently sloped
volcano made up from
many slow, steady flows
of hot lava. Low and
broad – like a warrior’s
shield.

Materials Erupted:
mainly liquid lava, so the
volcano is made of layers
of hardened lava.
– Non-explosive eruptions

Example: the volcanoes
of Hawaii
**Click picture for video.
Shield Volcanoes
Low silica level
 Low viscosity Lava
 High or low levels of gas
 Low to medium explosivity
 Flattened mound
 Resembles a warrior’s shield

Mauna Loa, Hawaii
Piton de la Fournaise
Surtsey, Finland
Composite
Volcanoes
Composite Volcanoes

A composite volcano is
a huge mountain-like
volcano. Layers build
up like frosting on a
cake forming a cone
with steep sides.

Materials Erupted:
sometimes lava,
sometimes rock
fragments.
– May have very
explosive eruptions

Example: Mount St.
Helens
**Click picture for video.
Composite Volcanoes
High in silica
 High viscosity magma
 High levels of gas
 Highly explosive
 Cone shaped
 Formed by layers of lava and ash

Mt. Rainier, Washington
Mt. Fuji, Japan
Mt. St. Helens, Washington
Cinder Cone
Volcanoes
Cinder cone volcanoes form
when solid rock and ash shoot
up into the air and fall back
around the volcano opening.
The cinder cone volcano has
steeply sloped sides.
Cindercones
Low silica lava
 High levels of gas
 “Fire-fountain” eruptions
 Commonly found on the flanks of shield
volcanoes
 Made from a pile of rock pieces
 Structurally weak

Cinder Cone Volcanoes

A cinder cone volcano is a
relatively small, volcano with
steep sides. It is where rock
and ash shoot up into the air
and fall back around the
opening.

Materials Erupted: small
pieces of hardened lava
(rock fragments) - called
cinders
– Moderately explosive

Example: Paricutin (Mexico)
**Click picture for video.
Pu'u ka Pele, Hawaii
(on the flanks of Mauna Loa)
Floreana Island, Galapagos
Puu OO, Hawaii