1. Volcanoes form as molten rock erupts
A volcano is an opening in earth’s crust through which molten rock, rock fragments, and hot gases erupt.
A volcano can erupt violently or gently

3. Volcanoes form as molten rock erupts
A volcano can have tremendous destruction even with limited molten rock reaching the surface
A volcano can
cause damage
through rock
fragments
starting fires

4. Volcanoes form as molten rock erupts
How violent a volcano is depends on the type of magma
The major portion of most magma is silica
Magma also
contains gases
which expand
as the magma rises

5. Volcanoes form as molten rock erupts
Magma that has less silica will flow better and bubble up and escape very gently
Magma will remain in the chamber until it cools or erupts

6. Volcanoes form as molten rock erupts
A great deal of material that erupts from volcanoes are rock fragments
The fragments form as
Escaping gas
bubbles pop,
tearing magma apart

7. Volcanoes form as molten rock erupts
Larger pieces of lava are thrown into the air cooling and hardening during their flight
Rocks of all sizes rip loose through volcanoes walls during eruptions

8. The smoke rising on a volcano is actually a mixture of ash and gases
The rock fragments form volcanic ash, volcanic cinders, and volcanic block/bombs
The smoke rising
on a volcano is
actually a mixture
of ash and gases

9. Volcanoes form as molten rock erupts
The main gases in magma are water vapor and carbon dioxide
During a eruption volcanic gases mix with rock fragments which form a pyroclastic flow, which is a dense cloud of superhot gases that race downhill.

10. Volcanoes form as molten rock erupts
Pyroclastic flows are the most dangerous type of volcanic eruption and can be as hot as 800 Celsius and travel faster than 100 miles per hour.

11. Volcanoes are common along tectonic plate boundaries where oceanic plates sink beneath other plates.

12. Volcanoes form as molten rock erupts
As a plate sinks it heats and begins to melt forming magma, if the magma reaches the surface it can build tall volcanic mountains.
More than 400 volcanoes about 80% of all active volcanoes are along the subduction zones in the pacific ocean.

13. Volcanoes form as molten rock erupts
The volcanoes around the pacific ocean form a belt called the ring of fire
There are 3 types of major volcanoes
A shield volcano is shaped like a broad flat dome. Its build up by many eruptions of lava that is low in silica and therefore flows easily and is spread out in thin layers.

14. Volcanoes form as molten rock erupts
The largest volcano on earth is the Mauna Loa which is a shield volcano.
2. A cinder cone is a cone shaped hill formed by the eruption of cinders and other rock fragments that pile up along a single crater

15. Volcanoes form as molten rock erupts
3. A composite volcano is a cone shaped volcano built of layers of lava and layers of rock fragments. Its magma is high in silicon and therefore pasty.
A composite volcano has violent eruptions for two reasons.

16. Volcanoes form as molten rock erupts
Expanding gases trapped in rising magma tend to cause explosions
Hardened lava often plugs these volcanoes, then making it harder for the volcano to erupt and when it does, big eruption!