1. VOLCANOES
Elisa Turiello Hernández
2º Bachillerato Bilingüe

2. Introduction
Volcanoes (word that comes from the ancient Roman god
Vulcano) are ruptures in the planet’s surface. From this
ruptures magma, ash and gases are or had been expelled.
Volcanoes communicate directly the superficial solid Earth’s
crust with the lower one.

3. Definitions
MAGMA: magma is the igneous mass made by molten rock
inside the Earth. Saying it in a easier way, magma is a mixture
made generally by molten rock, located inside the Earth.
LAVA: lava is the molten material that floods out of a volcano
when it erupts, forming fire rivers.
Even easier: the difference between magma and lava is
that the magma is inside the Earth and the lava has been
already expelled.

4. Volcanoes structures
A volcano is formed by different parts.
We have the magma chamber, a compartment communicated
to the surface by a kind of pipe called vent. The magma
chamber is the place underground where we can find the
magma that will be expelled from the crater, the volcano’s
“mouth”. The crater the higher place of the volcano and it’s
where the volcano as we know it (the “mountain” that we
see) expels the lava, that floods by the mountainside.

5. Types of magma
The type of magma usually is what makes volcanoes
erupt in a way or in another. Generally it depends on
the magma’s viscosity (we must understand “viscosity”
as the capacity of the magma to flow). If the magma is
very viscous, the eruption will be very hard. That is
because viscous magma offers resistance to exit and
when it finally is expelled, the eruption in harder. The
viscosity of magma depends on the silica content of
the magma and its temperature. If there is a lot of
silica, magma won’t be fluid at all, and so with
temperature (if the temperature is high, magma will be
more fluid).

6. Types of lava
There are three kind of lava, but number three is not very
important.
• Pāhoehoe Lava
It has a more or less smooth and plain surface. It’s very fluid
and it moves quickly.
• Aʻā Lava
It is characterize by a very irregular surface. It’s very viscous
and sticky, and it moves very slowly.
• Pillow Lava
It solidifies under the water, and because of that the lava
acquires a characteristic oval shape. It’s because of that
because it’s called “pillow lava”, because (with a lot of
imagination) it looks like a rock pillow.

7. Pahoehoe lava

8. Aʻā lava

9. Pillow lava

10. Differences between an extinct volcano and an actives one
Well, obviously an active volcano expels lava from his
crater and an extinct one doesn’t do anything, is just like
a mountain with a hole. But it’s more complicated than
that, and it is not clear at all. All I can say is that someone
says that it depends on the time (for example if a volcano
has erupt 25.000 years ago it is not active, but if it has
erupt 23.000 years ago, it is). Other ones say that it
depends if the volcano will in a future erupt again or not.
This part is not very clear, solo what can I say being sure
is…

11. This is an active volcano

12. This is NOT an activ volcano

13. Types of volcanic eruptions
The main ones are:
• Hawaiian: lava is accumulate in the volcano vent and then it
overfloods by the crater. The lava is very liquid, and it falls very
quickly by the mountainside forming lava rivers.
• Strombolian: it takes place when air bubbles are formed in the
magma. When this bubbles become bigger, they pull the lava out of
the crater and it falls down the mountainside. The lava is not very
viscous, but it isn’t as liquid as Hawaiian one.
• Vulcanian: tha magma that we see in these eruptions is very
viscous. Because of that it moves very slowly (tha lava is ʻAʻā
type).The explosions are very hard and they cause a high quantity of
ash and gas.

14. • Peléan: they are characterize by the high quantity of gases, ash,
dust and lava that is expelled. The lava of this kind of eruptions is
usually very liquid and for this reason it moves very quickly. This
type is one of the worst.
• Plinian or Vesuvian: the eruption of this kind is started too in the
magma chamber, where gases are stored and then released, pulling
lava out of the volcano. This lava floods easily by the mountainside
because it’s not very viscous and it reaches a very high speed. A lot
of gas is expelled, and it may forms an ash cloud, that can cause ash
and rocks rain. This occurred on 79 a.C. in Pompei, with Vesuvius’
eruption.

15. Vesuvio, Italia (Napoli)
That’s the double crater of the Vesuvio.

16. Photo of an eruption of the Vesuvio, which took place on
the Second War World.

17. A drawing of the Vesuvio inspirate on the eruption that
took place on 79 a.C. on Pompei, destroying the city.

18. Etna, Italia (Sicilia)
Of course in perpetual activity.

22. Laghi di Monticchio
They are two lakes in a extinct volcano crater. This water is
a natural source of sparkling water.

24. And now, watch the video. I hope you like it.
THE END