VOLCANIC ERUPTIONS

2. LEARNING COMPETENCY
Explain what happens when
volcanoes erupt. (S9ES-IIIb-27)

4. OBJECTIVES
1. describe the formation and composition of
magma and explain the effects of temperature
and composition and its viscosity;
2. relate the characteristics of magma with the
type of volcanic eruption;

5. OBJECTIVES
3. explain the process of volcanic eruption; and,
4. enumerate the material emissions of volcano
and describe the effects of material emissions
from volcanoes to humans and other living
things.

6. What Is It

7. What Is It
VOLCANOES – is a rupture in the Earth's
crust that allows lava, ash, and gases to
escape from a magma chamber below
the surface.

8. What Is It
VOLCANIC ERUPTIONS– is the expulsion of
gases, rock fragments, and/or molten lava
from within the Earth through a vent onto
the Earth's surface or into the atmosphere.

9. What Is It
TYPES OF
VOLCANIC
ERUPTIONS

10. What Is It
TYPES OF VOLCANIC ERUPTIONS
*PHREATIC *PHREATOMAGMATIC
*STROMBOLIAN *VULCANIAN
*PLINIAN

11. What Is It
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 a beginning of a larger
eruption.

12. What Is It
PHREATOMAGMATIC 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
pyroclastic materials called base surges are
observed.

13. What Is It
STROMBOLIAN a periodic, weak to violent
eruption characterized by fountain lava, just
like the Irazu Volcano in Costa Rica.

14. What Is It
VULCANIAN is 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.

15. What Is It
PLINIAN is the excessively explosive type of
eruption of gas and pyroclastic materials like in
Mt. Pinatubo in 1991.

16. What Is It
MAGMA is the molten rock which
lies underneath volcanoes. It is
formed at destructive plate
boundaries and is rich in silicate.
These are products of crustal rocks
(which are richer in silica than the
rock of the mantle).

17. What Is It
MAGMA AND ITS
COMPOSITION

18. What Is It
CRYSTAL CONTENT
Some magmas begin to crystallize as they
reach the surface. High temperature minerals
are formed as magma slowly cools down
followed by low temperature minerals. Magma
always contains crystals of high temperature.

19. What Is It
VISCOSITY
The magma’s silica content affects its viscosity, the
resistance of the fluid to flow. Low viscosity magma has low
silica content and is composed mostly of basalt. While
magma with rhyolite is viscous or high in viscosity due to
its high silica content. Temperature also affects the viscosity
of the magma. Magma with high temperatures have low
viscosity while magma with low temperatures have high
viscosity..

20. What Is It
TEMPERATURE
Temperature also affects the viscosity
of the magma. Magma with high
temperatures have low viscosity while
magma with low temperatures have high
viscosity.

21. What Is It
VOLATILE CONTENT
Magma contains small amounts of
dissolved gas (water vapor, Carbon
dioxide, etc.) which is released as
pressure is removed.

22. What Is It
VOLATILE CONTENT
Magmas formed by melting of mantle
rocks have generally low volatile contents,
but those formed by partial melting of
crustal rocks are often volatile-rich.

23. What Is It
Magmas formed by melting of mantle
rocks have generally low volatile
contents, but those formed by partial
melting of crustal rocks are often
volatile-rich.

24. What Is It
CLASSIFICATION
OF MAGMA

25. What Is It

26. What Is It
PROCESS OF
VOLCANIC
ERUPTION

27. What Is It
High temperature inside the Earth melts the solid
rocks in the mantle and turns it into a thick molten
mixture commonly known as magma. The continuous
melting of solid rocks and accumulation of additional
magma push it to the vent of a volcano, called
magma chamber. Magma contains dissolved gases
mostly water vapor, carbon dioxide, and sulfur
dioxide.

28. What Is It
As dissolved gases are released from the
magma, bubbles will begin to form through
the process called VESICULATION. This can
occur by decompression or
crystallization.

29. What Is It
In DECOMPRESSION, the confining
pressure is lowered when magma rises
which promotes bubble formation. This
process is similar to bubble formation in
soda bottles when opened.

30. What Is It
In the process of CRYSTALLIZATION of
anhydrous minerals, the vapor pressure of
the residual liquid of the cooling magma
increases leading to vesiculation. Bubbles
frozen in a porous or frothy volcanic rock
are called vesicles.

31. What Is It

32. What Is It
VOLCANIC HAZARDS are
phenomena arising from volcanic activity
that poses potential threat to people and
property.

33. What Is It
ASH FALL – pulverized
rocks, sand, gritty and harsh
glasses shoot out in the air by
volcano.

34. What Is It
MUD FLOW – mixture of water,
molten rocks and debris flowing
down from the side of volcano to
the ground. It is also called as
LAHAR.

35. What Is It
LAVA FLOW – streams of
molten rocks and other fragmented
materials emitted by erupting
volcano.

36. What Is It
PYROCLASTIC FLOW – fast
moving hot mixtures of gas, ash,
and molten rocks moving away
from the volcano to the ground.

37. What Is It

38. What Is It

39. What Is It

40. What Is It

41. Thank you!