3. Objectives:
At the end of this lesson, you will able
to:
Identify what is volcano.
Define what is ring of fire and how
volcano form.
State the types of volcanoes.
State the causes and effects of volcano
activity
4. Volcano
Volcano refer to the eruption of hot
molten lava from below the surface of
earth.
A volcano is a vent in the earth’s crust
through which lava, steam, ashes etc.
expelled
5. Ring of Fire
A zone along the edge of pacific Ocean
that has many Volcanoes and
Earthquakes.
The horseshoe shaped 40,000 kilometer
long belt it characterized by higher
volcanic activity.
The Ring of Fire is a string of volcanoes
that around the edge of the Pacific
Ocean.
6. A string of 45 volcanoes
stretches from the
southern tip of South
America, up along the
coast of north America,
across the Bering Strait,
down through Japan
and into New Zealand.
7. How are they formed?
When tectonic plates collide and
go through the process of
subduction, it sets the foundation
for a volcano. The overlapping of
the tectonic plates causes the
magma to break through the crust,
which is the cause of a volcanoes’
birth.
8. When temperature
and pressure rises,
the rock melts and
moves through the
surface and crust,
and releases gases
and magma
volcanic eruption
occurs.
9. The narrow opening of a volcano is called Vent.
The upper part of vent is a cup shaped depression
called Crater.
The rock material ejected during volcanic activity
is deposited on surface of Earth. It is called Lava
Pyroclastic Flow is fluidized mixture of solid to
semi-solid fragments. It is characterized by hot
expanding gases that flows down the flank of
volcanic edifice.
10. Definitions
Viscosity-the property of a fluid that resist the force
tending to cause the fluid to flow
Magma- molten material beneath or within the
earth’s crust, from which igneous rock is formed
Lava-the molten, fluid rock that issues from volcano
or volcanic event
Ash-the powdery residue of matter that remains
after burning
Caldera-a large crater formed by volcanic explosion
or by collapse of a volcano cone
11. Volcanoes can be in one
of the three phases:
ACTIVE, DORMANT, AND
EXTINCT.
12. ACTIVE VOLCANOES-are ones that have erupted in the
past 10,000 years, and that are likely to erupt again.
An example is Mt. Saint Helens in U.S.A
DORMANT VOLCANOES-are ones that have not erupted
in the past 10,000 years, but still have the possibility,
though unlikely. An example is Mt. Rainier in the
U.S.A.
EXTINCT VOLCANOES-are ones which no eruption has
occurred within historic times and future occurrences
are highly improbable. An example is Mt. Ashitaka in
Japan.
13. Hot springs and Geysers
A natural spring of mineral
water at a temperature of
20˚C (70˚F) or above, found
in areas of volcanic activity is
called HOTSPRING.
A hot spring that
intermittently send up
fountain like jets of water
and steam in to the air is
known as a GEYSER.
14.
15. Flood or Plateau Basalt
very liquid lava flows very
widespread emitted from
fractures. Examples: COLUMBIA
RIVER PLATEAU
Shield Volcano
liquid lava emitted from a central
vent, large sometimes had a
collapse caldera. Examples: Larch
Mountain, Mount Sylvania, Highland
Butte, Hawaiian Volcano
16. Cinder Cone
explosive liquid lava, small, emitted from a
central vent, it continued long enough,
may build up a shied volcano. Examples:
Mount Tabor, Mount Zion, Chamberlain
Hills, Pilot Butte, Lava Butte, Craters of the
Moon
Composite or Strato volcano
more viscous lavas, much explosive
(pyroclastic) debris, large, emitted from a
central vent. Examples: Mount Baker,
Mount Rainier, Mount St. Helens, Mount
Hood, Mount Shasta.
17. Volcanic Dome
very viscous lava, relatively small can be
explosive, commonly occurs adjacent to
craters of composite volcanoes.
Examples: Novarupta, Mount St. Helens
lave Dome, Mount Lassen, Shastina,
Mono Craters.
Caldera
very large composite volcano collapsed after
am explosive period, frequently associated
with plug domes. Examples: Crater Lake,
Newberry, Kilauea, Long Valley, Medicine
Lake, Yellowstone.
18. Causes of Volcanic Activity
When a part of the earth’s upper mantle
or lower crust melts, magma forms. A
volcano is essentially an opening or a
vent through which this magma and
dissolved gases it contains are discharged.
19. Effects Of Volcanic Eruptions
The effects of volcanic eruptions can be
divided into primary and secondary
effects
The primary effects are immediate and
come from the eruption itself.
The secondary effects results from the
primary effects.
20. Primary effects of volcanic
eruptions:
Volcanic gases-all magma contains dissolved
gases. These gases are mainly steam, carbon
dioxide and compounds of sulfur and chlorine.
Lava flows- these are streams of molten rock.
Pyroclastic flows-these are high speed
avalanches of hot ash, rock fragments and gas
which move down the sides of volcano. These
flows occur when the vent area or ash column
collapses.
21. Secondary effects of volcanic
eruption:
Lahars- these are mixture of water, rock, ash, sand and
mud that originate from the slopes of a volcano. Lahars
often happen because of heavy rainfall eroding volcanic
deposits.
Landslide- heat from cooling magma can cause
hydrothermal alteration of the rocks, turning sections of
them into clay
Flooding- explosive eruptions can change the surface
areas around a volcanic and disrupt drainage patterns,
leading to long term flooding
22. Conclusion
Volcanoes are caused
when molten rock
(magma) flows out
onto the earth’s
surface through
fissures that are
caused due to the
movements of plates
