Transcript What do we expect in a volcanic eruption?

Volcanoes
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
Mt St Helens
Mauna Loa
What do we expect in a
volcanic eruption?
• Solids lofted into atm
• Lava flows from
from others (called
some
pyroclastics. Better
• Range from mafic
than fireworks?
(e.g. basalt) to
• You bet!!!
felsic, like all ign rx • Rocks may form from
• Water
• Gases
fusing of pyroclastics
can range from dense
(tuff) to light (pumice)
Volcanoes
Vulcan’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
Sangay
Paricutin
Kilauea
Stromboli
Volcanoes
More 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
•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.
Fissure eruptions at Kilauea
Kilauea eruption
Shield Volcanoes
•Buildup primarily from basalt
flows.
•Long, low-angle slopes.
•Form of an inverted shield.
Mauna Loa
Cinder Cones
•Almost entirely pyroclastics.
•Short, steep slopes.
•Slopes at steepest angle
possible for size of
pyroclastics.
•Usually depression at top of
cone.
Cinder Cone
Stratovolcanoes
(Composite Cones)
•Pyroclastics build up.
•Lava flows extend laterally.
•Alternating lava and
pyroclastics.
Cotopaxi
Mt Hood
Spectacular Volcanic
Features
Crater Lake
Mt St Helens
Sangay
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
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?