1. Volcanic Eruptions
Mr. Silva

3. Vocabulary

4. Vocabulary
• Mafic lava- dark in color and is rich in
magnesium and iron.

5. Vocabulary
• Mafic lava- dark in color and is rich in
magnesium and iron.

6. Vocabulary
• Mafic lava- dark in color and is rich in
magnesium and iron.
• Felsic lava- lighter in color when cools,
high in silica.

7. Vocabulary
• Mafic lava- dark in color and is rich in
magnesium and iron.
• Felsic lava- lighter in color when cools,
high in silica.

8. Vocabulary
• Mafic lava- dark in color and is rich in
magnesium and iron.
• Felsic lava- lighter in color when cools,
high in silica.
• Pahoehoe- (puh-HOY-hoy) wrinkles that
are formed when lava cools rapidly.

9. Vocabulary
• Mafic lava- dark in color and is rich in
magnesium and iron.
• Felsic lava- lighter in color when cools,
high in silica.
• Pahoehoe- (puh-HOY-hoy) wrinkles that
are formed when lava cools rapidly.

10. Vocabulary
• Mafic lava- dark in color and is rich in
magnesium and iron.
• Felsic lava- lighter in color when cools,
high in silica.
• Pahoehoe- (puh-HOY-hoy) wrinkles that
are formed when lava cools rapidly.
• Aa- (AH-ah) refers to the sharp, blocky
texture of volcanic rock.

11. Vocabulary

12. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.

13. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.

14. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.

15. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.

16. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.
• Volcanic ash- Particles less than 2mm

17. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.
• Volcanic ash- Particles less than 2mm

18. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.
• Volcanic ash- Particles less than 2mm
• Volcanic dust- Particles less than .25mm

19. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.
• Volcanic ash- Particles less than 2mm
• Volcanic dust- Particles less than .25mm

20. Vocabulary
• Pillow lava/Pillow basalts- round blobs
of lava that separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.
• Volcanic ash- Particles less than 2mm
• Volcanic dust- Particles less than .25mm
• Lapilli- Particles less than 64 mm

21. Vocabulary

22. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.

23. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.

24. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.
• Volcanic block- largest pyroclastic particle that
blast from the fissure or vent.

25. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.
• Volcanic block- largest pyroclastic particle that
blast from the fissure or vent.

26. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.
• Volcanic block- largest pyroclastic particle that
blast from the fissure or vent.
• Shield Volcano- covers a wide area and
generally result from lava eruptions.

27. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.
• Volcanic block- largest pyroclastic particle that
blast from the fissure or vent.
• Shield Volcano- covers a wide area and
generally result from lava eruptions.

28. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.
• Volcanic block- largest pyroclastic particle that
blast from the fissure or vent.
• Shield Volcano- covers a wide area and
generally result from lava eruptions.
• Cinder Cone- formed from explosive eruption.

29. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.
• Volcanic block- largest pyroclastic particle that
blast from the fissure or vent.
• Shield Volcano- covers a wide area and
generally result from lava eruptions.
• Cinder Cone- formed from explosive eruption.

30. Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.
• Volcanic block- largest pyroclastic particle that
blast from the fissure or vent.
• Shield Volcano- covers a wide area and
generally result from lava eruptions.
• Cinder Cone- formed from explosive eruption.
• Composite Volcano- results from altering
layers of pyroclastic material and lava.

31. Vocabulary

32. Vocabulary
• Stratovolcanoes- also known as
composite volcanoes, highest volcanic
mountains.

33. Vocabulary
• Stratovolcanoes- also known as
composite volcanoes, highest volcanic
mountains.

34. Vocabulary
• Stratovolcanoes- also known as
composite volcanoes, highest volcanic
mountains.
• Crater- funnel shape around the vent of
the volcano.

35. Vocabulary
• Stratovolcanoes- also known as
composite volcanoes, highest volcanic
mountains.
• Crater- funnel shape around the vent of
the volcano.

36. Vocabulary
• Stratovolcanoes- also known as
composite volcanoes, highest volcanic
mountains.
• Crater- funnel shape around the vent of
the volcano.
• Caldera- basin in the crater that is
created when slippage occurs.

37. Volcanic Eruptions
• The lava that erupts from volcanoes allows
us to determine firsthand the material that
emerges from the mantle.
• Scientist has discovered that there are two
general types of lava.
– Mafic lava
– Felsic lava

38. Mafic Lava
• Dark in color when hardens.
• Rich in Magnesium and Iron.
• Forms much of the ocean crust.
• When crust cools rapidly,
surface will form a crust.

39. Felsic Lava
• Lighter in color when
hardens
• Common in
continental crust
• Contains much silica,
with lesser amounts of
iron and Magnesium

40. Rock Formations
• When mafic lava cools and
forms wrinkles there called
pahoehoe (puh-HOY-hoy)
• Can break into jagged chunks
to form aa (Ah-ah)
• When lava flows into the ocean
and cools rapidly, it often
separates and forms pillow
lava.

41. Kinds of Eruptions
• The kind of lava that reaches the surface
determines the force the volcano will
erupt.
• Lava that contains large amounts of
trapped gases produces a more explosive
eruption of lava.

42. Oceanic Volcanoes
• Usually produced by mafic lava.
• Mafic lava is very hot and thin, and flows
like almost as easy as water.
• Gases escape easier from mafic lava, so
eruptions are usually quiet.
• Will flow from the opening like a red hot
river.

43. Continental Volcanoes
• Most commonly comprised of felsic lava.
• Tends to be cooler and thicker.
• Contains large amounts of trapped gases,
mostly water vapor and carbon dioxide.
• When fissure or vent opens, gases escape
explosively sending molten particles
shooting into the air.

44. Volcanic Rock Fragments
• Felsic lava explode throwing pyroclastic
material into the air.
• Formed when lava cools too fast or is
sprayed into the air and solidifies.
– Volcanic ash
– Volcanic dust
– Lapilli (luh-PIL-ie)
– Volcanic bombs
– Volcanic blocks

45. Volcanic Rock Fragments
• Volcanic ash • Volcanic dust
– Particles less than 2mm – Particles less than .25 mm

46. Volcanic Rock Fragments
• Lapilli • Volcanic bomb
– Particles less than 64mm – Round or spindle shape

47. Volcanic Rock Fragments
• Volcanic Blocks
– Largest pyroclastic material, can be as big as
a house!

48. Volcanic Features
• Volcanic activity produces a variety of
characteristic features on the earth.
• The lava and pyroclatic material ejected during
eruption can build up around the vent.
• These piles are known as volcanic cones; they are
classified into three different types.
– Shield Volcano
– Cinder Cones
– Composite Volcano

49. Shield Volcano
• Covers a wide area
• Generally results from lava eruption
• Layers of hot mafic lava flow out around
the vent, harden, and slowly build up to
form a cone.
• The Hawaiian Islands are a chain of
shield volcanoes.

50. Cinder Cone
• Made up of solid fragments ejected from
the volcano.
• Most cinder cones have very steep slopes,
often close to 40 degrees.
• Rarely more than a few hundred meters
high.

51. Strato / Composite Volcano
• Many volcanoes have both quiet and
explosive eruptions.
• Composite volcanoes are formed as a
result of alternating layers of lava and
pyroclastic material.
• Also known as stratovolcanoes

52. Craters/ Calderas
• A crater is a funnel-shaped pit at the top of
the volcanic vent .
• Formed when material is blown out of the
volcano by explosion.
• Calderas are formed when slippage or
sinking occurs in the crater.

53. Super Volcanoes
• Yellowstone National Park
23

54. Predicting Volcanic Eruptions
• Volcanic eruptions can be one of earth’s
most destructive natural phenomena.
• Scientist are still making progress toward
increase there abilities in predicting
volcanic activity.
• Scientists use instruments much like the
one they use with earthquake prediction.

55. Predicting Volcanic Eruptions
• Things they look for:
– Temperature changes within the rock
– Fracturing of rocks from pressure build-up
– Increase in # earthquake around volcano
– Increase is strength of earthquakes
– Bulging surface
– Change in gases given off by the volcano in
the area