11. Learning Objectives
At the end of the lesson, the students will be able to:
1. determine what is a volcano;
2. determine the common types of volcanoes;
3. differentiate active and inactive volcanoes;
4. describe different types of volcanic eruptions; and
5. explain what happens when volcanoes erupt.
12. 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
14. Strato volcanoes
• are cone-shaped
mountains that have
been built up from
layers of ash and lava.
They are generally the
tallest type of volcano
and are known for their
violent explosions.
15. Strato volcanoes
• Bubbles of gas build up in the
magma — which has a high
silica content — and explode
creating volcanic ash,
consisting of tiny gritty sharp
fragments of glassy snap-
frozen magma and rock from
the sides of the volcano vent.
17. Shield volcanoes
• This flatter type of
volcano is named after
the Roman Centurion
shield shape of the
volcano made by
repeated gentle flows
of lava down its slopes.
18. Shield volcanoes
• The magma is very hot
and runny, so they are
less likely to build up
and create explosions
— although they still
can.
20. Caldera volcanoes
• This type of volcano
has the coolest and
stickiest magma. It
tends to erupt so
violently its top
collapses and leaves a
large basin shape in its
place.
21. Caldera volcanoes
• Some caldera
volcanoes are up to 90
kilometres across and
are called
supervolcanoes.
22. Caldera volcanoes
• Examples of super
volcanoes are
Yellowstone in the US
and Lake Toba in
Indonesia.
Yellowstone
Lake Toba
24. • Active Volcano
• Inactive Volcano
• Potentially Active/Dormant
Mt. Kilauea in Hawaii is the most
active volcano in the world.
25. Active Volcanoes
• have eruptive histories or
there has been a recorded
eruption in historical times.
• Examples: Mt. Kilauea (Hawaii),
Mt. Mayon (Ph), Mt. Taal (Ph), Mt.
Etna (Italy), Mt. St. Helens (WA),
and Mt. Merapi (Indonesia) Mt. Mayon is the most active
volcano in the Philippines.
26. Active Volcanoes
• There are currently 23 active
volcanoes being monitored
by PHIVOLCS.
• Dateable erupted materials
confirm that they erupted
within the last 10,000 years.
Mt. Vesuvius (Italy, 79 AD) is considered
the most dangerous eruption in history.
27. Active Volcanoes
• Four most active volcanoes
in the Philippines:
• Mt. Mayon
• Mt. Taal
• Mt. Kanlaon
• Mt. Bulusan
Pyroclastic cone of Mt. Taal
28. Active Volcanoes
• Mt. Mayon
• last eruption was in 2018, 52
historical eruptions
• The famous “perfect cone”
signifies Mayon’s structure as a
stratovolcano. Mt. Mayon, Albay
29. Active Volcanoes
• Mt. Taal
• last eruption was in 1977,
33 eruptions
• Taal Lake represents a
collapsed caldera
covering 267 km2. Mt. Taal, Batangas
30. Active Volcanoes
• Mt. Kanlaon
• last eruption in 2016, 30
eruptions
• The highest mountain in Visayas
with several flank vents around
the summit crater.
Mt. Kanlaon, Negros Occidental
31. Active Volcanoes
• Mt. Bulusan
• last eruption in 2017, 18
eruptions
• It is part of the Irosin Caldera,
a complex volcanic field
spanning most of Sorsogon. Mt. Bulusan, Sorsogon
32. Inactive Volcanoes
• have no eruptive histories,
are heavily weathered, and
will never erupt again.
• Examples: Mt. Arayat
(Pampanga) and Seven
Lakes of San Pablo (Laguna)
Lake Sampaloc, one of the
Seven Lakes of Laguna
34. Inactive Volcanoes
● Mt. Arayat
• Mount Arayat’s hiking trails are
well-known, and there is a rich
history of folklore and
superstition surrounding the
mountain.
Mt. Arayat, Pampanga
35. Inactive Volcanoes
● Seven Lakes of Laguna
• Also known as the Seven Lakes of
San Pablo.
• Lake Calibato, Lake Palakpakin,
Lake Muhikap, Lake Sampaloc,
Lake Yambo, Lake Pandin, and
Lake Calibato.
Lake Yambo, Laguna
36. Potentially Active Volcanoes (dormant volcanoes)
• have no eruptive histories and no recent dateable materials,
but are morphologically recent (i.e. un-eroded) and in some
instances present signs of activity or remnant heat.
• PHIVOLCS lists 26 potentially active volcanoes.
• Examples: Mt. Arayat (Pampanga) and Seven Lakes of San
Pablo (Laguna)
37. Potentially Active Volcanoes
● Mount Apo
• the country’s highest peak, which
showcases sulfuric steam and
hosts a geothermal plant
• It is a stratovolcano and is
considered a national park. Mt. Apo, Cotabato
38. Potentially Active Volcanoes
● Cuernos de Negros
• also known as Mount Talinis
• This range exhibits areas of
geothermal alteration and
steaming, and will soon host a
geothermal plant. Mount Talinis, Negros Island
39. Potentially Active Volcanoes
● Mt. Isarog
• Isarog is located in
Camarines Sur.
• It is a stratovolcano famous
for its rich and unique
biodiversity. Mt. Isarog, CamSur
41. Phreatic or hydrothermal
• is a stream-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. Shown on the
right is our Taal Volcano.
42. Phreatomagmatic
• means that erupting magma
reacts with external water,
e.g. ground water, lake
water, sea water etc. As a
result, a large column of
very fine ash and high-
speed and sideway
emission of pyroclastics
called base surges are
observed.
43. Strombolian
• A periodic of weak to
violent eruption
characterized by
fountain lava, just like
the Irazu Volcano in
Costa Rica.
44. Vulcanian
• characterized by tall
eruption columns that
reach up to 20km high
with pyroclastic flow
and ashfall tephra like
that of Paricutin
Volcano in Mexico.
47. Flowing hot lava
can incinerate,
bury and bulldoze
things in its path
but at least is
usually moving
slowly enough for
humans to get out
of its way.
48. For a start there's
hot gas and rock
(called pyroclastic
flows or surges)
that tumble down
the slopes
49. Then there are
"volcanic bombs"
made of rock that
can fly out of the
vent and an
eruption cloud
made of ash and
gas that shoots up
into the air.
