3.1.2 Tectonic Hazards
Part 1: Types of volcanoes
a. What are volcanoes and what states can they be in?
A volcano is an opening in the Earth’s crust where magma - a mixture of red-hot liquid
rock, mineral crystals, rock fragments and dissolved gases from inside the planet erupts
onto the surface
Volcanoes are found in three states:
● Extinct
○ Will never erupt again
● Dormant
○ Haven't erupted in 2000 years
● Active
○ Are erupting or have erupted recently and are likely to again
b. What are the different types of volcanoes?
Type Diagram Description How formed Examples
,Cinder Cones Circular or oval cones made up of Cinder cones result from Mount Etna, Sicily
small fragments of lava from a eruptions of mostly small pieces
single vent that have been blown of scoria and pyroclasts that
up. build up around the vent. Most
cinder cones erupt only once.
Cinder cones may from as flank
vents on larger volcanoes, or
occur alone
Composite Steep-sided volcanoes are Composed of many layers of Mount Fuji, Japan
These volcanoes are usually tall volcanic rocks, usually made Mount St Helens, USA
conical mountains composed of from high-viscosity lava, ash and
lava flows and other ejecta in rock debris. Composite
alternate layers. volcanoes are made of cinders,
ash and lava.
Shield Bowl/shield shaped volcanoes with Formed by the eruption of Kilauea, Hawaii
long gentle slopes made of basaltic low-viscosity Mauna Loa, Hawaii
lava flows. Fernandina Island, Galapagos
Islands
Lava domes Steep-sided mound created from Formed when erupting lava is Paricutin, Mexico
lava which had solidified and built too thick to flow, creating a Sunset Crater, USA
up over hundreds of thousands of steep sided mound near the
years. volcanic vent. They are built up
by slow eruptions of high
viscosity lava (not runny). These
produce violent, explosive
eruptions. But their lava
generally does not flow far from
the originating vent.
Caldera A volcano which has a large Gases trapped in the magma Yellowstone, USA
depression, which can eventually chamber eventually cause an Crater Lake, USA
flood extremely explosive eruption
which can destroy the upper
part of the volcano. This leaves a
large depression in the ground
which can eventually flood with
, water.
Part 2: Volcanic processes and hazards
a. What types of volcanic eruptions can we have?
Explosive:
A lot of gas is trapped within magma, causing pressure to build until the
magma erupts explosively out of the volcano.
E.g Eyjafjallajokull - Iceland 2010
Effusive:
If magma has low viscosity (it is runny), gas can escape easily, so lava flows
are formed. These eruptions are more gentle.
When magma is more vicious (sticky) it can’t flow when it reaches the surface
so it therefore builds up a lava dome.
Part 1: Types of volcanoes
a. What are volcanoes and what states can they be in?
A volcano is an opening in the Earth’s crust where magma - a mixture of red-hot liquid
rock, mineral crystals, rock fragments and dissolved gases from inside the planet erupts
onto the surface
Volcanoes are found in three states:
● Extinct
○ Will never erupt again
● Dormant
○ Haven't erupted in 2000 years
● Active
○ Are erupting or have erupted recently and are likely to again
b. What are the different types of volcanoes?
Type Diagram Description How formed Examples
,Cinder Cones Circular or oval cones made up of Cinder cones result from Mount Etna, Sicily
small fragments of lava from a eruptions of mostly small pieces
single vent that have been blown of scoria and pyroclasts that
up. build up around the vent. Most
cinder cones erupt only once.
Cinder cones may from as flank
vents on larger volcanoes, or
occur alone
Composite Steep-sided volcanoes are Composed of many layers of Mount Fuji, Japan
These volcanoes are usually tall volcanic rocks, usually made Mount St Helens, USA
conical mountains composed of from high-viscosity lava, ash and
lava flows and other ejecta in rock debris. Composite
alternate layers. volcanoes are made of cinders,
ash and lava.
Shield Bowl/shield shaped volcanoes with Formed by the eruption of Kilauea, Hawaii
long gentle slopes made of basaltic low-viscosity Mauna Loa, Hawaii
lava flows. Fernandina Island, Galapagos
Islands
Lava domes Steep-sided mound created from Formed when erupting lava is Paricutin, Mexico
lava which had solidified and built too thick to flow, creating a Sunset Crater, USA
up over hundreds of thousands of steep sided mound near the
years. volcanic vent. They are built up
by slow eruptions of high
viscosity lava (not runny). These
produce violent, explosive
eruptions. But their lava
generally does not flow far from
the originating vent.
Caldera A volcano which has a large Gases trapped in the magma Yellowstone, USA
depression, which can eventually chamber eventually cause an Crater Lake, USA
flood extremely explosive eruption
which can destroy the upper
part of the volcano. This leaves a
large depression in the ground
which can eventually flood with
, water.
Part 2: Volcanic processes and hazards
a. What types of volcanic eruptions can we have?
Explosive:
A lot of gas is trapped within magma, causing pressure to build until the
magma erupts explosively out of the volcano.
E.g Eyjafjallajokull - Iceland 2010
Effusive:
If magma has low viscosity (it is runny), gas can escape easily, so lava flows
are formed. These eruptions are more gentle.
When magma is more vicious (sticky) it can’t flow when it reaches the surface
so it therefore builds up a lava dome.
