Volcanic Activity

1. VOLCANIC
ACTIVITY

2. Objectives

3. How volcanoes formed?
⦿ “Volcanoes are formed when tectonic
plates collide and go through the
process of subduction (The sideways and
downward movement of the edge of a plate of the earth's
crust into the mantle beneath another plate.), it sets the
foundation for volcano. The overlapping
of the tectonic plates causes the magma
to break through the crust, which is the
cause of a Volcanoes’ birth.”

4. Places where volcanoes occur
⦿ “Most volcanoes occur near the edges of
plates. When plates push together, one
plate slides beneath the other.”
⦿ “Most volcanoes occur in the basin of the
Pacific Ocean, also known as the Ring of
Fire. Most volcanoes are situated on the
edges of tectonic plates. One of the largest
of these tectonic plates, the Pacific plate, is
the area around which the majority of
volcanoes lie.”

5. Pacific , Ring of Fire

6. Pacific , Ring of Fire
⦿ There are 452 volcanoes dotting the Ring of
Fire
⦿ 75 % of all the world's volcanoes
⦿ This 25,000-mile-long ring includes volcanoes
on Antarctica, extends along the coast of South
America, up Central America and Mexico,
along the West Coast of the United States and
the coast of California, marches across Alaska
to Russia, extends down to Japan, over the
Philippines, down to New Zealand and back to
Antarctica. It also includes volcanoes in Hawaii
and other islands in the Pacific Ocean.

7. Volcanic Hotspots
⦿ “A volcanic "hotspot" is an area in the
mantle from which heat rises as a
thermal plume from deep in the Earth.
High heat and lower pressure at the
base of the lithosphere (tectonic plate)
facilitates melting of the rock. This melt,
called magma, rises through cracks and
erupts to form volcanoes.”

8. Volcanic Hotspots
⦿ “The melted rock, known as magma,
often pushes through cracks in the crust
to form volcanoes. Hot spot volcanism is
unique because it does not occur at the
boundaries of Earth's tectonic plates,
where all other volcanism occurs.
Instead it occurs at abnormally hot
centers known as mantle plumes.”

9. Volcanic Hotspots
⦿ More than a hundred
hotspots beneath
the Earth's crust have been
active during the past 10
million years. Most of these
are located under plate
interiors (for example, the
African Plate), but some
occur near diverging plate
boundaries.
⦿ As the tectonic plate moves
over the stationary hot spot,
the volcanoes are rafted
away and new ones form in
their place. This results in
chains of volcanoes, such as
the Hawaiian Islands.

10. How Volcanoes Erupt
⦿ Hot, molten rock (magma) is buoyant (has a lower
density than the surrounding rocks) and will rise up
through the crust to erupt on the surface.
● Same principle as hot air rising, e.g. how a hot air balloon works
⦿ When magma reaches the surface it depends on how
easily it flows (viscosity) and the amount of gas (H2O,
CO2, S) it has in it as to how it erupts.
⦿ Large amounts of gas and a high viscosity (sticky)
magma will form an explosive eruption!
● Think about shaking a carbonated drink and then releasing the cap.
⦿ Small amounts of gas and (or) low viscosity (runny)
magma will form an effusive eruption
● Where the magma just trickles out of the volcano (lava flow).

11. Types of Volcanic Eruption

12. ⦿Explosive Eruption
⦿Effusive Eruption
⦿Magmatic Eruption
⦿Phreatomagmatic Eruption
⦿Phreatic Eruption

13. ⦿Explosive
Eruption
- Magma is torn apart
as it rises and reaches
the surface in pieces
known as pyroclasts.
- An explosive
eruption is a volcanic
term to describe a
violent,explosive type
of eruption

14. ⦿Effusive
Eruption
- An effusive
eruption is a type of
volcanic eruption in
which lava steadily
flows out of
a volcano onto the
ground. Effusive
eruption differs from
explosive eruption,
wherein magma is
violently fragmented
when expelled from
a volcano.

15. Magmatic eruptions (*)
⦿ Magmatic eruptions
produce juvenile clasts during explosive
decompression from gas release. They
range in intensity from the relatively
small lava fountains on Hawaii to
catastrophic Ultra-Plinian eruption
columns more than 30 km (19 mi) high,
bigger than the eruption of Mount
Vesuvius in 79 that buried Pompeii.

16. Magmatic eruptions
⦿ Hawaiian: A Hawaiian
eruption is a type of volcanic
eruption where lava flows from
the vent in a relatively gentle,
low level eruption; it is so
named because it is
characteristic
of Hawaiian volcanoes.
Hawaiian eruptions usually
start by the formation of a
crack in the ground from which
a curtain of
incandescent magma or
several closely spaced magma
fountains appear

17. Magmatic eruptions
⦿ Strombolian: Strombolian
eruptions are relatively mildly
explosive. Strombolian
eruptions consist of ejection
of incandescent cinder, lapilli,
and lava bombs, to altitudes of
tens to a few hundreds of
meters. The eruptions are small
to medium in volume, with
sporadic violence.

18. Magmatic eruptions
⦿ Vulcanian: Vulcanian eruptions are
a type of volcanic eruption, named
after the volcano Vulcano. It was
named so following Giuseppe
Mercalli's observations of its 1888-
1890 eruptions. In Vulcanian
eruptions, highly viscous magma
within the volcano make it difficult
for vesiculate gases to escape.
Similar to Strombolian eruptions,
this leads to the buildup of high gas
pressure, eventually popping the
cap holding the magma down and
resulting in an explosive eruption.

19. Magmatic eruptions
⦿ Peléan: They can occur
when viscous magma, typically
of rhyolitic or andesitic type, is
involved, and share some
similarities with Vulcanian
eruptions. The most important
characteristic of a Peléan
eruption is the presence of a
glowing avalanche of hot volcanic
ash, a pyroclastic flow. Formation
of lava domes is another
characteristical feature. Short flows
of ash or creation of pumice cones
may be observed as well.

20. Magmatic eruptions
⦿ Plinian: also known
as Vesuvian eruptions. Plinian
eruptions are marked by
columns of gas and volcanic
ash extending high into
the stratosphere, the second
layer of Earth's atmosphere.
The key characteristics are
ejection of large amount
of pumice and very powerful
continuous gas blast eruptions.

21. Phreatomagmatic eruptions (*)
⦿ Phreatomagmatic eruptions are eruptions
that arise from interactions
between water and magma. They are
driven from thermal contraction (as
opposed to magmatic eruptions, which are
driven by thermal expansion) of magma
when it comes in contact with water. This
temperature difference between the two
causes violent water-lava interactions that
make up the eruption.

22. Phreatomagmatic eruptions
⦿ Surtseyan: takes place in
shallow seas or lakes. These
eruptions are
commonly phreatomagmatic
eruptions, representing violent
explosions caused by rising
basaltic or andesitic magma
coming into contact with
abundant, shallow groundwater
or surface water.

23. Phreatomagmatic eruptions
⦿ Submarine: Submarine
eruptions are
those volcano eruptions which
take place beneath the surface
of water. These occur at
constructive
margins,subduction zones and
within tectonic plates due
to hotspots.

24. Phreatomagmatic eruptions
⦿ Subglacial: Subglacial eruptions are a
type of volcanic eruption characterized
by interactions between lava and ice,
often under a glacier. The nature of
glaciovolcanism dictates that it occurs
at areas of high latitude and
high altitude. It has been suggested
that subglacial volcanoes that are not
actively erupting often dump heat into
the ice covering them,
producing meltwater. This meltwater
mix means that subglacial eruptions
often generate
dangerous jökulhlaups (floods)
and lahars.

25. Phreatic eruptions (*)
⦿ Phreatic eruptions (or steam-
blast eruptions) are a type of
eruption driven by the
expansion of steam. When cold
ground or surface water come
into contact with hot rock or
magma
it superheats and explodes,
fracturing the surrounding rock[
and thrusting out a mixture of
steam, water, ash, volcanic
bombs, and volcanic blocks

26. Types of Lava
⦿ Aa’s: Pronounced “ah-ah”, this is a basaltic lava that doesn’t flow very
quickly. It looks like a slowly moving mass of hot jello, with cooler, rough
surface. Once it hardens, the sharp spiny surface of a’a lava is
extremely difficult to walk across. These types of lava erupt at
temperatures above 1000 to 1100 degrees C.
⦿ Pahoehoe: Pronounced “pa-ho-ho”, this type of lava is much
thinner and less viscous than a’a. It can flow down the slopes of a
volcano in vast rivers. The surface of the lava congeals into a thin crust
that looks very smooth. Pahoehoe lava can also form lava tubes, where
the rock hardens around a fast-moving liquid core. When that core
flows out of the tube, a long tunnel remains. Pahoehoe erupts at
temperatures of 1100 to 1200 C.
⦿ Pillow Lava: Pillow lava is typically found erupting from
underwater volcano vents. As soon as the lava contacts the water, it’s
cooled down and forms a hardened shell. As more lava issues from the
vent, the shell of lava cracks and more “pillows” come out of these
cracks.

27. Difference Between Magma and Lava
⦿Magma and lava are the same
substance in two different forms.
Magma is molten rock that is
found beneath the earth's crust,
while lava is what magma
becomes once it reaches the
surface and erupts from a volcano
or crack in the earth.

28. Method for predicting Volcanic
Eruption
⦿ Ground deformation: Swelling of a volcano signals that magma has
accumulated near the surface. Scientists monitoring an active volcano
will often measure the tilt of the slope and track changes in the rate of
swelling. An increased rate of swelling, especially if accompanied by an
increase in sulfur dioxide emissions and harmonic tremors is a high
probability sign of an impending event. The deformation of Mount St.
Helens prior to the May 18, 1980 eruption was a classic example of
deformation, as the north side of the volcano was bulging upwards as
magma was building up underneath. Most cases of ground deformation
are usually detectable only by sophisticated equipment used by
scientists, but they can still predict future eruptions this way. The
Hawaiian Volcanoes show significant ground deformation; there is
inflation of the ground prior to an eruption and then an obvious deflation
post-eruption. This is due to the shallow magma chamber of the
Hawaiian Volcanoes; movement of the magma is easily noticed on the
ground above.

29. Sources
⦿ www.slideshare.net
⦿ www.reference.com/science/volcanoes-occur
⦿ www.education.nationalgeographic.com/educati
on/encyclopedia/hot-spot/
⦿ https://en.wikipedia.org/wiki/Types_of_volcanic_
eruptions#Magmatic_eruptions
⦿ https://en.wikipedia.org/wiki/Lava
⦿ https://www.reference.com/science/difference-
between-magma-lava-5ecc64127ba16ce
⦿ https://en.wikipedia.org/wiki/Prediction_of_volca
nic_activity

30. Questionnaire/Quiz
1.) _________ are formed when tectonic
plates collide and go through the process
of subduction.
A. Lava
B. Magma
C. Volcanoes
D. Muscles

31. Questionnaire/Quiz
2.) Most volcanoes occur in the basin of
the Pacific Ocean, also known as the ____
__ _____
A. Ring of Fire
B. Cheese ring
C. Tectonic plates
D. Island

32. Questionnaire/Quiz
3.) There are ___ volcanoes dotting the
Ring of Fire
A. 452
B. 7107
C. 1
D. 13

33. Questionnaire/Quiz
4.) “A volcanic “_______" is an area in the
mantle from which heat rises as a thermal
plume from deep in the Earth.
A. Splash
B. Power
C. Hotspot
D. Current

34. Questionnaire/Quiz
5.) An ________ eruption is a volcanic
term to describe a violent, _______ type
of eruption
A. Explosive eruption
B. Magmatic Eruption
C. Effusive Eruption
D. Airplane

35. Questionnaire/Quiz
6.) ____ is what magma becomes once
it reaches the surface and erupts from a
volcano or crack in the earth.
A. Lava
B. Magma
C. Oil
D. Fish

36. Questionnaire/Quiz
7.) _____ is molten rock that is found
beneath the earth's crust.
A. Air
B. Water
C. Earth
D. Magma

37. Questionnaire/Quiz
8.) _______ eruptions (or steam-blast
eruptions) are a type of eruption driven by
the expansion of steam.
A. Phreatic eruption
B. Effusive eruption
C. Explosive eruption
D. Picolo

38. Questionnaire/Quiz
9.)______________ eruptions are
eruptions that arise from interactions
between water and magma
A. Baseline eruption
B. Phreatomagmatic eruption
C. Perimeter eruption
D. Paint area eruption

39. Questionnaire/Quiz
10.) ________ eruptions
produce juvenile clasts during explosive de
compression from gas release.
A. Melting eruption
B. Explosive eruption
C. Effusive eruption
D. Magmatic eruption

40. Essay

41. Reporters
⦿ Almazan, Angelo A.
⦿ Ventura, Joshua O.