Volcanoes These notes go on p. 11 of your inb !!!
-
Upload
latifah-pugh -
Category
Documents
-
view
23 -
download
0
description
Transcript of Volcanoes These notes go on p. 11 of your inb !!!
VOLCANIC SETTINGS (PLATE BOUNDARIES)
CONTINENTAL divergence
Ocean-Continent
ConvergenceOcean
Divergence
Ocean-Ocean Convergence
VOLCANIC ACTIVITY
Active Volcanoes: recent eruptions, active magma source Mt. Etna, Italy
Dormant Volcanoes: no recent eruptions, but still has an active source of magma Mt. St. Helens, USA
Extinct Volcanoes: no recent eruptions, no source of magma Northwestern Hawaiian Islands
TERMS TO KNOW:
Viscosity- the resistance of lava to flow• Ex: The more viscous the lava, the thicker
and stickier the material & the harder it is to flow (honey vs. water)
• depends on the amount of silica
•the type of crust being melted determines the amount of silica!
TERMS TO KNOW:
Hot Spot- random upwelling of magma NOT associated with convection in the mantle create a special type
of volcanism not associated with plate boundaries
Ex: Hawaii, Yellowstone & Iceland
Kaui
Molokai
Hawaii
Oahu
Lanai
Maui
3 TYPES OF VOLCANIC CONES:
1. Cinder Cones: explosive eruptions, small but steep slopes, pyroclastics
Cinder Cone
3 TYPES OF VOLCANIC CONES:
2. Shield: non-explosive eruptions, fluid basaltic lava, gentle broad slopes
3 TYPES OF VOLCANIC CONES:
3. Composite Cones/Stratovolcanoes: alternating between lava and pyroclastics, explosive and non-explosive eruptions, very steep/tall
MID-OCEAN RIDGES & OCEANIC HOT SPOTS
Effusive Eruption (non-violent): low viscosity, flows easily, gases escape easily
Magma Type: mafic (dark, dense seafloor)
Volcano Type: Shield Volcanoes
Lava Type: Pillowhttp://www.youtube.com/watch?v=DdIUuUY0L9c
C
BASALTIC LAVA TYPES
Pillow Basalts (underwater)http://www.youtube.com/watch?v=DdIUuUY0L9c
AA lava- jagged lava
Pahoehoe- ropey, smooth lava
C
SUBDUCTION BOUNDARIES
Mostly Explosive Eruption (violent): high viscosity, does not flow easily, gases trapped, hard to predict explosions
Magma Type: felsic & mafic
Volcano Type: Composite Cone (Stratovolcanoes) & cinder cones
Other Features: gas flows, calderas, aerial bombs
C
PYROCLASTIC FLOWS
searing superheated gas and volcanic ash & dust; very fast
Also called “Nuee Ardente”
http://www.youtube.com/watch?v=-H_HZVY1tT4Mt. St. Helens Eruption
http://www.youtube.com/watch?v=WxlRpuTed6gPyroclastic Flow
C
CONTINENTAL DIVERGENT BOUNDARY & CONTINENTAL HOT SPOTS
C
Explosive Eruption (violent): high viscosity, does not flow easily, gases trapped, hard to predict explosions (always explosive!)
Magma Type: felsic or rhyolitic
Volcano Type: Composite Cone (Stratovolcanoes), cinder cones, dome complexes
Other Features: gas flows, calderas, aerial bombs, pyroclastic flows
Silica Content
Melting Temp.
Gas Content
Viscosity
Type of Eruption
Location
Least (~50%)
Basaltic Magma
Least
Least viscous
Rarely explosive
Highest
Rifts, oceanic hot spots
Andesitic Magma
Intermediate (~60%)
Intermediate
Intermediate
Sometimes explosive
Intermediate
Subduction boundaries
Rhyolitic Magma
Most (~70%)
Most
Most viscous
Usually explosive
Lowest
Continental hot spots
Magma and Erupted Materials