10. Lava Tubes at Volcanic National Park, HI
Fig. 5-3a, p. 137
11. Lava Textures
Pahoehoe (pah-hoy-hoy) is Aa (ah-ah) is characterized by a
characterized by its smooth and rough, clinkery surface and is
often ropey or wrinkly surface and what most viscous and hot lava
is generally formed from more flows look like.
fluid lava flows.
Fig. 5-4a, p. 137
12. Lava Composition
 Felsic Lava: high percentage (>63%) of silica, and
trapped gasses; highest viscosity, lowest temperatures
 Andesitic Lava: (52-63%) of silica
 Mafic Lava: (45-52%) of silica + high percentage of
Magnesium (Mg); typically occur at subduction zones
 Balsitic Lava: (45-52%) of silica + high percentage of
Iron (Fe); typically occur at oceanic divergent pages
 Ultramafic Lava: (=<45%) of silica; lowest vicsosity,
13. Columnar Jointing at Devil’s Post Pile
National Monument, CA
Fig. 5-5b, p. 138
14. Inversion of Topography
 1. Lava flows into the
 2. Lava cools and
extrusive igneous rocks.
 3. Areas adjacent to
the flow erode more
easily then the flow
 4. Over time, an
inversion is produced.
Fig. 5-6ab, p. 139
15. Craters of the Moon National Monument, ID
Fig. 5-3b, p. 137
16. VOLCANIC TYPES
17. Types of Volcanoes
18. Fig. 5-18, p. 149
19. Plutonic Bodies
20. Formation of a Caldera
Fig. 5-9a-d, p. 142
21. Crater Lake, OR Caldera
Caldera Floor of Crater Lake
Wizard Island, Crater Lake, OR
22. Shield Volcanos
Fig. 5-10a, p. 143
23. Shield Volcano, Mauna Loa, HI
•Low Viscosity Basalt Flows
•Most common in ocean basins
24. Cinder Cones
Fig. 5-11a, p. 144
25. Cinder Cones, Mojave Desert, CA
•Eruptions are short-lived.
•Large, bowl-shaped craters.
•Ash builds up rapidly.
•Few lava flows.
•Lava flows typically from base of cone.
26. Stratovolcanoes (Composite Cones)
Fig. 5-13a, p. 146
27. Stratovolcano, Mt. Rainier, WA
•Composed of layered sills.
•Lahars, or volcanic mud flows are common.
•Have steep slops near summit.
•Lava flows from andesite.
28. Lahar Flows, Mt. Pinatubo, Philippines
Fig. 5-14a, p. 146
29. Lava Domes
Fig. 5-15b, p. 147
30. Lava Dome, Mt. St. Helens, WA
•Composed of felsic magma.
•Formed from intermediate magma forced up under great pressure.
•Highly unstable, will collapse under weight of rock.
Fig. 5-15a, p. 147
31. Mt. Saint Helens Eruption
32. VOLCANIC ERUPTIONS
33. Types of Erruptions
34. Fig. 5-17, p. 148
35. Fissure Eruptions
 Generated along a
 Composed of low-
 Commonly occur along
 Also common on the
edges of large Fissure eruption in Iceland
 Produces a curtain of
36. Columbia River Basalt Plateau
Fig. 5-19, p. 150
37. Volcanic Explosive Index
38. Primary Effects of Volcanoes
 Pyroclastic Flows
 Ash Fall
 High Temperatures
39. Secondary Effects of Explosions
 Suffocation from Ash
 Asphyxiation from Volcanic Gasses
 Temperatures Decreases
40. Environmental Effects
 Involved in the formation of continental crust and
offset weathering and erosion
 Provide nutrient rich soils
 By trapping clouds at their peaks, water for
 Agriculture based cultures are attracted to their
41. Volcanic Gasses
 Water Vapor
 Carbon Dioxide
 Sulfur Dioxide
 Hydrogen Sulfide
 Carbon Monoxide
Gasses emitted from fumaroles at the Sulfur Works in
Lassen Volcanic National Park, CA
Fig. 5-2, p. 136
42. Effects of Volcanoes on Climate
 Nucleation, condensation, and sedimentation of aerosols (acid rain)
 Change in Albedo from ash cloud
 Tropospheric cooling from the addition of sulfur to the stratsophere
 Ozone destruction through the formation of atomic chlorine
45. Discovery Questions
 What does it take to be classified as a super
 When did the last one occur? Why is their
controversy about the date?
 What would be the primary effects of such an
 For those who survived the initial eruption, what
would happen in the following months, or years?
 How did the Toba explosion effect the evolution of
46. DISTRIBUTION &
47. Distribution of Volcanoes
 More common along both divergent than convergent plate boundaries.
 Mainly composed of intrusive magma flows.
 Composed of mafic magma that forms beneath spreading plates.
 Pyroclastic materials are not common because lava is fluid.
 Water pressure prevents gasses from expanding and escaping.
Fig. 5-20, p. 151
48. USGS Volcano Hazards Program
53. Lassen Peak, CA
 Largest Lava Dome in the World
54. Lassen Peak Diagram
Concept Art, p. 154
55. Mid-Atlantic Ridge & Iceland
56. Formation of Surtsey Island, Iceland
57. Important Monitoring Techniques
Fig. 5-23, p. 159
58. Fumarole Gas Monitoring
 Chemically-selective sensors
for SO2 and CO2 measure
gas concentrations and a wind
sensor measures wind speed
 Data from solar-powered
stations are transmitted to
GOES geostationary satellite
and then down to
observatories every 10
minutes, providing near real
time data on degassing of
59. Ground Deformation Monitoring
 Electronic Distance Meters
 determine the horizontal movements
that occur on active volcanoes
 leveling surveys to measure vertical
 Global Positioning Systems
 allows us to measure horizontal
motions much more accurately and
conveniently, and also to estimate
vertical motions in the same survey
60. Remote Sensing
 The Advanced Very High
Resolution Radiometer (AVHRR)
is a space-borne sensor
embarked on the NOAA family
of polar orbiting platforms.
 The primary purpose of these
instruments is to monitor clouds
and to measure the thermal
emission (cooling) of the Earth.
 The main difficulty associated
with these investigations is to
properly deal with the many
limitations of these instruments,
especially in the early period
(sensor calibration, orbital drift,
limited spectral and directional
61. WHAT ARE BLACK
62. Hydrothermal Vents
 Distributes heat and
drives water circulation
in the ocean through
 Provides energy source
in the form of hydrogen
sulfide to benthic
 Distributes minerals and
composition of the ocean
63. Hydrothermal Plume
Black smoker smoker
Magma White clam
64. Location of Major Vent Systems
65. Learn More About Vents