A volcano is a vent in the Earth's crust that allows magma and erupted material to reach the surface. It includes the cone of erupted material surrounding the vent. The main parts of a volcano are the vent, crater, and volcanic cone. Volcanoes can have different shapes depending on the type of material they erupt, including shield, cinder cone, and composite cone volcanoes. Volcanic eruptions can be either explosive or effusive and pose hazards like pyroclastic flows, lava flows, ash falls, and noxious gases.

1. What is a volcano?
• A volcano is a vent
or 'chimney' that
connects molten rock
(magma) from within
the Earth’s crust to
the Earth's surface.
• The volcano includes
the surrounding cone
of erupted material.
vent
cone
magma
chamber
conduit

2. What are the parts of a Volcano?
1. VENT- the vent is the
opening from which
lava flows. Dust,
ash, and rock
particles can also be
thrown out of the
vent!

3. 2. Crater- the top of
the volcano. It is a
funnel shaped pit.
It is formed when
the material
explodes out of the
vent!

4. 3. Volcanic cone- is the
pile of lava, dust,
ashes, and rock
around the vent. It
can be found in
different shapes!

5. Volcanoes do not all look alike. Their
shape is based on what type of
materials they erupt. There are three
main kinds, or shapes, of volcanoes.

6. Shield ( Basic) Cone
Shield Volcanoes are enormous features built up only from layers of lava.
They produce lots of lava but they tent not to erupt violently.
Mauna Loa Hawaii -USA
250 miles
10,000m
Layers of Lava Lava Flow

7. Ash and Cinder Cone
Paracutin - Mexico
Layers of Ash
and Cinder
Volcanic Bombs
Pipe
The volcano is built up of layers of ASH.
When it erupts it is normally with great explosive force.
3,000m

8. Composite Cone
The volcano is built up of alternate layers of LAVA and ASH.
They can explode with great violence.
Mt St Helens - USA
Conelet
Dyke
Crater
Ash layer
Lava Layer Flank
eruption
Lava
Flow
Crust
Pyroclastic Flow

9. The GALAPAGOS Islands are a volcanic
group of islands 600 miles off the coast of
Ecuador on the equator.

10. Kilauea on Hawaii is a good example of
a shield cone, with less explosive
eruptions and less viscous lava.

11. Crater Lake in Oregon is a CALDERA formed
from the collapse of the gigantic volcano Mount
Mazama. Wizard Island in the center of the lake
is a small CINDER CONE.

12. Mt Rainier and Mt St Helens are good
examples of composite cones, with
explosive eruptions and erupted materials
such as ash, bombs, and blocks.
Mt St Helens
Mt Rainier

13. Explosive Eruptions
Mt. Redoubt
• Explosive volcanic
eruptions can be
catastrophic
• Erupt 10’s-1000’s km3 of
magma
• Send ash clouds >25 km
into the stratosphere
• Have severe
environmental and
climatic effects
• Hazardous!!!
Above: Large eruption column and ash
cloud from an explosive eruption at Mt
Redoubt, Alaska

14. • Three products
from an explosive
eruption
– Ash fall
– Pyroclastic flow
– Pyroclastic surge
Explosive Eruptions
Pyroclastic flows on
Montserrat, buried the
capital city.

15. Effusive Eruptions
• Effusive eruptions are
characterized by
outpourings of lava on to
the ground.
Hawaii

16. • Pyroclastic flow
• Lahars/Mud flows
• Pyroclastic fall
• Lava flow
• Noxious Gas
• Earthquakes
Volcanic Hazards

17. Pyroclastic Flow
• For example,
eruption of
Vesuvius in 79 AD
destroyed the city
of Pompeii