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Lecture 5 Volcanism. Physical Geology. Lecture Outline. I Characteristics of Volcanoes II Types of Volcanoes A) Shield Volcanoes i. Description ii. Composition iii. Eruption Features B) Composite Volcanoes i. Description ii. Composition iii. Eruption Features

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Presentation Transcript
slide1

Lecture 5

Volcanism

slide2

Physical Geology

Lecture Outline

I Characteristics of Volcanoes

II Types of Volcanoes

A) Shield Volcanoes

i. Description

ii. Composition

iii. Eruption Features

B) Composite Volcanoes

i. Description

ii. Composition

iii. Eruption Features

iv. Distribution

C) Cinder Cones

i. Description

ii. Composition

iii. Eruption Features

III Lava Floods

IV Submarine Eruptions

V Living with Volcanoes

VI Conclusions

slide3

Physical Geology

Characteristics of Volcanoes

Vent

Fumarole

Crater

Caldera

Volcanic Domes

slide4

Physical Geology

Characteristics of Volcanoes

Vents and Fumaroles

vent : the opening at

the earth's surface

through which

volcanic materials

are extruded.

fumarole : a hole or vent from which volcanic

fumes or vapors issue.

slide5

Physical Geology

Characteristics of Volcanoes

Craters

crater : a basin-like rimmed structure at the

top or on the flanks of a volcanic cone;

it is formed by explosion or collapse

Mt Erebus, Antarctica

Mt Poas, Coast Rica

Halemaumau, Hawaii

slide6

Physical Geology

Characteristics of Volcanoes

Calderas

Aniakchak, Alaska

Kaguyak, Alaska

Crater Lake, Oregon

caldera : a large basin-shaped

volcanic depression, more or less

circular. the diameter of which is

many times greater than that of the

included vent or vents, irrespective

of the steepness of the walls or the

form of the floor.

slide7

Physical Geology

Characteristics of Volcanoes

Caldera Formation

slide8

Physical Geology

Characteristics of Volcanoes

Volcanic Dome

volcanic (lava) dome: steep-sided mound

built by magma too viscous to flow far

from vent before crystallizing and cooling.

slide9

Physical Geology

Types of Volcanoes

Shield Volcanoes

Composite Volcanoes

Cinder Cones

slide10

Physical Geology

Types of Volcanoes

Shield Volcanoes

  • Slope: Gentle (2-10o)
  • Height: up to 10 km
  • Composition: Flow layers
      • Basaltic
  • Eruption: Effusive
      • Low-Viscosity Lava
          • A'a
          • Pahoehoe
      • Flank Eruptions
  • Other Characteristics:
      • Lava Ponds and Tubes
      • Spatter Cones

Mauna Loa, Hawaii

slide11

Physical Geology

Types of Volcanoes

Shield Volcanoes

slide12

Physical Geology

Types of Volcanoes

Shield Volcanoes

pahoehoe

a'a

slide13

Physical Geology

Types of Volcanoes

Shield Volcanoes

lava tube : a hollow space beneath the surface of a

solidified lava flow, formed by the

withdrawal of molten lava after the

formation of a surficial crust

spatter cone: A low steep-sided

cone of spatter built by lava

fountains along a fissure or

around a vent

slide14

Physical Geology

Types of Volcanoes

Composite Volcanoes

Slope: < 33o

Height: 1000 - 4000 m

Composition: Layers of pyroclastic fragments

and lava flows

      • Andesitic
  • Eruption: Explosive
  • Other Characteristics:
      • Magma blocks conduit
      • Glowing clouds

Mt St Helens and Mt Ranier

slide15

Physical Geology

Types of Volcanoes

Composite Volcanoes

Mount St. Helens

May 18, 1980

8:32:00 a.m. The bulging north flank that geoscientists had watched develop since March is intact. It had clearly grown by 450 feet in some areas, and by late April was estimated to be growing at five feet a day.

8:32:10 a.m. A 5.1 magnitude earthquake about 1 mile beneath the mountain causes the north flank to slide. Tendrils of steam burst from the mountain, releasing pressure bottled up in magma below.

8:33:00 a.m. A cubic mile of mountain gives way, traveling at 70 to 150 mph, and superheated rocks in the volcano's core are suddenly exposed, shooting a lateral blast of gas north, incinerating everything in its path. Huge glaciers on the mountain's peak melt instantly.

8:33:20 a.m. The blast is over but the mountain begins to pulverize as the eruption vents its full fury, sending a thick, 3-mile-wide ash cloud 80,000 feet into the sky.

http://seattlepi.nwsource.com/mountsthelens/grapherupt.shtml

slide16

Physical Geology

Types of Volcanoes

Composite Volcanoes

slide17

Physical Geology

Types of Volcanoes

Composite Volcanoes

http://www.3dnworld.com

slide18

Physical Geology

Types of Volcanoes

Composite Volcanoes

slide19

Physical Geology

Types of Volcanoes

Cinder Cones

  • Slope: Steep (33o)
  • Height: < 300 m
  • Composition: Pyroclastic fragments
      • Various
  • Eruption: Explosive
  • Other Characteristics:
      • Short-lived

Paricutin, Mexico

Cinder Cone,Mauna Kea, Hawaii

slide20

Physical Geology

Lava Floods

slide21

Physical Geology

Lava Floods

The Columbia Plateau

slide22

Physical Geology

Submarine Eruptions

Kavachi, Solomon Islands

slide23

Physical Geology

Submarine Eruptions

The Mid-Ocean Ridge

slide24

Physical Geology

Volcanic Hazards