for science

1. Volcanoes
Earth Science: EDUC 212

2. ANATOMY, TECTONIC SETTING, MECHANICS OF
VOLCANIC ERUPTIONS, ERUPTIVE STYLES,
FORECASTING ERUPTIONS, CONSTRUCTIVE
ASPECTS OF VULCANISM
VULCANISM:

3. • is the eruption of molten rocks called magma onto the earth’s surface
through a vent.
• The driving force of vulcanism is the plate tectonic motion created by
the movement of molten rocks in the mantle caused by thermal
convection current.
VULCANISM:

4. ANATOMY OF A VOLCANO:

5. A volcano is a mountain that opens
downward to a pool of molten rock below
the surface of the earth.
Volcano

6. Volcanoes are formed when magma
from within the Earth's upper mantle
works its way to the surface.
How are volcanoes formed?

7. Different Parts of a Volcano

8. Tectonic Settings Most common magma type Typical types of volcanoes Most common hazards Example
Divergent plate boundary basaltic Mid-ocean ridge, fissures and vents,
shield
Lava flows, ejecta Mid-ocean ridges, iceland
Intracontinental extension Basaltic or bimodal silicic/basaltic Varied: fissures and vents, flood
eruptions, cinder cones,
stratovolcanoes, caldera complexes
Lava flows; explosive volcanism
including pyroclastic flows, ejecta,
ash fall, lahars
Columbia river; Rio Grande rift;
Basin and Range, East African rift.
Convergent Plate Boundary Generally intermediate, but can be
silicic or basaltic
stratovolcanoes Explosive volcanism; pyroclastic
flows, ejecta, lahars, ash fall.
Cascades volcanoes including Mt.
St. Helens, Pacific Rim, Central
America and Carribean volcanoes,
Krakatoa, tambora Galunggung ,
pelee.
Hot spots under oceanic plate
Hot spots under continental plate
Basaltic
silicic
Shield volcano
Caldera complex
Lava flows
Explosive volcanism
Hawaii
yellowstone
TECTONIC SETTINGS OF VOLCANOES

9. MECHANICS OF VOLCANIC ERUPTION

10. •Active
•Dormant
•Extinct
The Classifications of Volcanoes

11. ACTIVE VOLCANO - An active volcano is one that erupts regularly.
DORMANT VOLCANO - A dormant volcano is one that has not erupted
for many years, although there is still some activity deep inside.
EXTINCT VOLCANO - An extinct volcano is a volcano that is no longer
active.

16. •Because of the friction of the plates’
movement.
•When pressure builds up, eruptions
occur.
Why do Volcanoes erupt?

17. MATERIALS OF VIOLENT ERUPTIONS
- An explosive eruptions is a volcanic eruption of the most violent
eruption type. Example is Mt. St. Helens in 1980 which such eruptions
result when sufficient gas has dissolved under pressure within a viscous
magma.
- Violent eruptions can send rocks, dust, gas and pyroclastic materials
up to 20 km into the atmosphere at a rate of up to 100, 000 tonnes per
second.

18. What is a pyroclastic flow?

19. •A pyroclastic flow is a
fluidized mixture of solid to
semi-solid fragments and
hot, expanding gases that
flows down the sides of a
volcano

20. What is lahar?

21. •
A lahar is a type of
mudflow or debris flow
composed of pyroclastic
material, rocky debris,
and water.

22. What is pumice?

23. Pumice is a light,
porous volcanic rock
that forms during
explosive eruptions.

24. What is the Ring of Fire?

25. •
•The Pacific Ring of Fire
is an area of frequent
earthquakes and
volcanic eruptions
encircling the basin of
the Pacific Ocean

26. Types of Volcanic
cone and its Factor
*Composite cone
*Cinder cone
*Shield type of volcanic cone

27. Composite cones
Composite cones are some of the most
easily recognizable and imposing volcanic
mountains, with sloping peaks rising several
thousand meters above the landscape.

28. Composite cone

29. Cinder cones
Cinder cones, sometimes called scoria
cones or pyroclastic cones, are the most
common types of volcanic cones. They form
after violent eruptions blow lava fragments
into the air, which then solidify and fall
as cinders around the volcanic vent. Usually
the size of gravel, these cinders are filled with
many tiny bubbles trapped in the lava as it
solidifies. Cinder cones stand at heights of
tens of meters to hundreds of meters.
Cinder cones may form by themselves or
when new vents open on larger, existing
volcanoes. Mauna Kea, a volcano on the
American island of Hawaii, and Mount Etna, a
volcano on the Italian island of Sicily, are both
covered with hundreds of cinder cones.

30. Cinder cone

31. Shield Volcano
-Shield volcanoes are the largest volcanoes on Earth that
actually look like volcanoes (i.e. not counting flood basalt flows).
The Hawaiian shield volcanoes are the most famous examples.
-Shield volcanoes are almost exclusively basalt, a type
of lava that is very fluid when erupted. For this reason these
volcanoes are not steep (you can't pile up a fluid that easily runs
downhill). Eruptions at shield volcanoes are only explosive if water
somehow gets into the vent, otherwise they are characterized by
low-explosivity fountaining that forms cinder cones and spatter
cones at the vent, however, 90% of the volcano is lava rather
than pyroclastic material.

32. Shield Volcano

33. STYLE OF
VOLCANIC ERUPTION
*Phreatic or Hydrothermal eruption
*Phreatomagmatic eruption
*Strombolian eruption
*Vulcanian eruption
*Plinian eruption

34. Phreatic eruptions or Hydrothermal
*are steam-driven explosions that occur when water beneath the
ground or on the surface is heated by magma, lava, hot rocks, or new
volcanic deposits (for example, tephra and pyroclastic-flow deposits)

35. Phreatic eruptions or
Hydrothermal

36. Phreatomagmatic eruption
- is an explosive water-magma interaction. Large amounts
of steam and magmatic gases are emitted.

37. Phreatomagmatic eruption

38. Strombolian eruption
A type of volcanic activity which produces frequent,
moderate eruptions. The lava is basaltic, but
sufficiently viscous for entrapped gases to build up a
pressure which is released in continuous small
explosions.

39. Strombolian eruption

40. Vulcanian eruption-
An explosive type of
volcanic eruption that occurs when the
pressure of entrapped gases in a
relatively viscous magma becomes
sufficient to blow off the overlying crust
of solidified lava.

41. Vulcanian eruption

42. Plinian eruptions
also known as Vesuvian
eruptions, are volcanic
eruptions marked by their
similarity to the eruption
of Mount Vesuvius in 79 AD.
The eruption was described in
a letter written by Pliny the
Younger; it killed his uncle,
Pliny the Elder.

43. Plinian eruptions
*Eruption of Mt.Vesuvius

46. CONSTRUCTIVE ASPECTS OF VOLCANISM

47.  Provide nutrients to the surrounding soil. Volcanic ash
contains minerals that are beneficial to plants.
 The internal heat associated with young volcanic systems
has been harnessed to produce geothermal energy.
 Most of the minerals mined in the world, such as copper,
gold, silver, lead and zinc are associated with magmas
found deep within the roots of extinct volcanoes.

48. That’s all!
GOD BLESS YOU!