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Volcanoes g110 lecture prepared by Bob Hall revised 7/31/2000 Points to Be Covered on Volcanos Products of eruptions Lava properties vs composition Fissure eruptions Types of volcanoes Distribution of volcanoes World Famous Kilimanjaro Fujiyama Mt St Helens Mauna Loa Mt St Helens

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volcanoes g110

Volcanoesg110

lecture prepared by Bob Hall

revised 7/31/2000

points to be covered on volcanos

Points to Be Covered on Volcanos

Products of eruptions

Lava properties vs composition

Fissure eruptions

Types of volcanoes

Distribution of volcanoes

world famous
World Famous

Kilimanjaro

Fujiyama

Mt St Helens

Mauna Loa

Mt St Helens

what do we expect in a volcanic eruption
Lava flows from some

Range from mafic (e.g. basalt) to felsic, like all ign rx

Water

Gases

Solids lofted into atm from others (called pyroclastics. Better than fireworks?

You bet!!!

Rocks may form from fusing of pyroclastics can range from dense (tuff) to light (pumice)

What do we expect in a volcanic eruption?
volcanoes vulcan s story
VolcanoesVulcan’s Story
  • Magma/lava viscosity related to composition.
  • Less viscous lavas flow more easily.
  • This releases dissolved gases more easily.
  • Less likely to produce a violent eruption.
  • More likely to be distributed farther.
gassy volcanoes giving us atmosphere
Gassy Volcanoes –Giving us atmosphere

Sangay

Kilauea

Stromboli

Paricutin

volcanoes more on water and gases

VolcanoesMore on Water and Gases

What gas is overwhelmingly the most abundant volcanic gas?

Water vapor. Over (95%)

Isn’t that how we got our oceans, streams, etc.

Our hydrosph, yes. And our atm

Oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogen sulfide (stinky), hydrogen chloride (??), sulfur dioxide (bad guy?), ammonia

fissure eruptions

Fissure Eruptions

Erupt basaltic lava.

Low viscosity, moves fast and far.

Where are these fissures?

The ocean floor in spreading centers.

Anywhere on land?

Yes, wherever rifting has occurred.

Check out the Colombia Plateau. Great thicknesses of basalt lava.

shield volcanoes

Shield Volcanoes

Buildup primarily from basalt flows.

Long, low-angle slopes.

Form of an inverted shield.

Mauna Loa

cinder cones

Cinder Cones

Almost entirely pyroclastics.

Short, steep slopes.

Slopes at steepest angle possible for size of pyroclastics.

Usually depression at top of cone.

Paicutin

stratovolcanoes composite cones

Stratovolcanoes(Composite Cones)

Pyroclastics build up.

Lava flows extend laterally.

Alternating lava and pyroclastics.

Mt Hood

Cotopaxi

distribution of volcanoes

Distribution of Volcanoes

Convergent plate boundaries

Circum-Pacific Ring of Fire

Alpine-Himalayan Belt

Divergent plate boundaries: oceanic ridges

Mid-Atlantic Ridge

terms used in the study of volcanoes
Technical Terms

Cinder cone

Convergent boundary

Divergent boundary

Fissure eruption

Pyroclastics

Rift

Shield volcano

Spreading center

Stratovolcano

(Composite cone)

Non-technical terms

Lava

Viscosity

Terms used in the study of volcanoes
student responsibilities on volcanoes
Student Responsibilities on Volcanoes
  • What are the products of volcanic eruptions?
  • How do we interrelate magma/lava viscosity, stored gases, violence of an eruption, and distance of transport of the volcanic products?
  • What are fisssure eruptions, shield volcanoes, cinder cones, and stratovolcanoes?
  • How do we explain the global distribution of volcanoes?