This document discusses different types of volcanoes. It defines an active volcano as one currently erupting or expected to erupt soon, with approximately 500 considered active. Dormant volcanoes are not currently erupting but have in the past, while extinct volcanoes will never erupt again. The document also examines factors that influence magma viscosity like temperature, chemical composition, and dissolved gas content. Finally, it outlines different types of volcanic eruptions like phreatic, phreatomagmatic, Strombolian, and Plinian eruptions.

5.  An opening in Earth’s crust through which
molten rock, gases, and ash erupt.
 A volcano is an opening in the Earth’s crust
that allows molten rock, gases, and debris to
escape to the surface.

7. 1. Active Volcanoes
 A volcano is classified as active if it is currently
erupting or is expected to erupt in the near
future. Approximately 500 volcanoes on Earth
are classified as active, not including volcanoes
that are submerged under the oceans. Between
50 and 70 active volcanoes erupt every year..

8. 2. Dormant Volcanoes
 A dormant volcano is one that is not currently
erupting but has erupted within recordable
history and is expected to erupt again in the
future.

9. 3. Extinct Volcanoes
 Extinct volcanoes are considered dead and are not
expected to ever erupt again.

11.  Magma inside the volcano has high
temperature. As the magma is continously
heated, it goes up. As it rises, gas bubbles
are developed. The gas bubbles are trapped
and expanded causing the molten material to
swell also, resulting in a gradual increase in
pressure within the volcano. When the
pressure exceeds the strength of the
overlying rock, fracturing occurs. The
resulting breaks lead to a further drop in
confining pressure, which in turn causes even
more gas bubbles to form.

12.  At the summit, there is an opening which
may be either be a crater or a caldera.
 Crater – is a funnel-shaped opening at the
top of a volcano
 Caldera – is formed when a part of the wall
collapses following an explosive eruption.
 A volcano can have one crater, like Mayon
Volcano, or more than one, like Taal Volcano
that has 47 craters.

15. 1. Magma’s temperature
 The higher the temperature of magma is, the
lower is its viscosity.
 Is the property of the material’s resistance to
flow. It is also described as the liquid’s
thickness and stickiness. The more viscous and
thicker the material is, the greater is its
resistance to flow. For instance, syrup is more
viscous than water.

16.  The viscosity of magma decreases with
temperature.
 The higher the temperature of magma is, the
lower its viscosity is. As lava, flows, it cools
and begins to harden, its ability to flow
decreases and eventually stops.

17. 2. Chemical Composition
 Magmas with high silica content are more
viscous than those with low silica content.
 The magma that contains less silica is relatively
fluid and travels far before solidifying.

18. 3. Amount of Dissolved Gases it Contains
 Gas dissolved in magma tends to increase its
stability to flow. Therefore, in near-surface
environments, the loss of gases makes magma
more viscous, forming a dome or a columnar.

23.  Is a steam-driven
eruption as the hot
rocks come in
contact with water.
It is short-lived,
characterized by ash
columns but may be
an onset of a larger
eruption.

24. Is a violent eruption
due to the contact
between water and
magma. As a result,
a large column of
very fine ash and
high-speed and
sideway emission of
pyroclastics called
base surges are
observed.

25. - A periodic weak
to violent
eruption
characterized by
fountain lava,
just like the Irazu
Volcano in Costa
Rica.

26. -characterized by
tall eruption
columns that
reach up to 20 km
high with
pyroclastic flow
and ashfall tephra
like that of
Paricutin Volcano
in Mexico.

27. -excessively
explosive type of
eruption of gas
and pyroclastics,
just like our
Pinatubo Volcano
in Zambales.

28. -characterized by
tall eruption
columns that
reach up to 20 km
high with
pyroclastic flow
and ash fall tephra
like that of
Paricutin Volcano
in Mexico.

29. -are built from
ejected lava
fragments. They
have steep slope,
wide crater and
are the most
abundant of the
three major
volcano types.

30. -also known as
STRATOVOLCANOES,
are large, nearly
perfect sloped
structure formed
from alternate
solidification of both
lava and pyroclastic
deposits.