Transcript of Video on Youtube: Volcano Eruption – The Eruption of Mount St Helens 1980 22 minutes.
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Video on Youtube: Volcano Eruption The Eruption of Mount St
Helens 1980 22 minutes
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VOLCANOES
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Lithosphere Side vent Pipe Central vent Lava flows Dike Sill
Magma chamber Magma chamber Magma, which originates in the
asthenosphere......rises through the lithosphere to form a crustal
magma chamber. Lavas erupt through a central vent and side
vents,......accumulating on the surface to form a volcano.
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Magma reservoir Lava flow Flank eruption Central vent 10 km 60
km Shield volcanoes are built up by the accumulation of thin
basaltic flows. Most commonly found in Hawaii Mafic lava flows out
and runs parallel to oceans (not the triangle type of some other
volcanoes)
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Mauna Loa (Hawaii) Mauna Loa (Hawaii)
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Crater Lava dome Volcanic domes are bulbous masses of felsic
lava, which are so viscous that they pile up over the vent. Similar
to Mt St Helens The lava is so viscous that they end up piling up
and then later blow all in one time.
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Mount St. Helens (Washington) Mount St. Helens
(Washington)
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Central vent filled with rock fragments Cinder-cone volcanoes
are made of layers of ejected material that dip away from the
crater at the summit. The vent is filled with fragmental debris.
Successive layers of ejected material
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Cerro Negro (Nicaragua) Cerro Negro (Nicaragua)
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Central vent filled from previous eruption Stratovolcanoes are
built from alternating layers of pyroclastic material and lava
flows. Riblike dikes strengthen the cone. Pyroclastic layers Lava
flows Radiating dikes Alternating layers of pyroclastic and
lava
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Mount Fuji (Japan) Mount Fuji (Japan)
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Craters are found at the summits of most volcanoes. Mt. Etna
(Sicily, Italy) Mt. Etna (Sicily, Italy)
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Calderas result when a violent eruption empties a magma
chamber, which collapses, leaving a large, steep-walled basin.
Crater Lake (Oregon) Mount Mazama created Crater Lake in
Oregon
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Mt. Mazama STAGE 1 Fresh magma triggers an eruption of lava and
ash.
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STAGE 2 Eruption continues, and the magma chamber becomes
partly depleted.
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STAGE 3 The mountain summit collapses into the empty
chamber.
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STAGE 4 A lake forms in the caldera. Crater Lake
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Lava Cinder cones Cinder cones Earlier flows Fissures Highly
fluid basalt erupting from fissures forms widespread layers rather
than mountains.
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Continental crust Continental crust Continental mantle
lithosphere Continental mantle lithosphere Continental volcanic
belt Active volcano over hot spot Active volcano over hot spot
Mid-ocean ridge Island arc Ocean plate Ocean plate Mantle plume
Mantle plume Rising magma Rising magma Hot spot Hot spot Extinct
volcano At ocean-ocean convergent boundaries, magmas give rise to
volcanic island arcs erupting basaltic and andesitic lavas. Magmas
formed at ocean-continent convergences give rise to volcanoes
erupting andesitic lavas. Plate separation at a mid-ocean ridge
results in basaltic volcanism. Plate motion over hot spots creates
midplate chain of basaltic volcanic islands.
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Direction of plate movement Older extinct volcanoes Hot-spot
volcano Asthenosphere Lithosphere Hot-spot ASIA NORTH AMERICA
PACIFIC OCEAN Equator Emperor Seamounts Midway Hawaii Tahiti
Galpagos Islands 64.7 Ma 56.2 55.4 55.2 48.1 39.9 43.4 42.4 Midway
27.7 Direction of plate movement Nihau 5.5 Kilauea 0 Hawaii hot
spot The Pacific Plate has moved northwest over the Hawaiian hot
spot resulting in a chain of volcanic islands. The ages of the
mountains suggest plate movement of about 100 mm/yr A sharp change
in direction has been dated at about 43 Ma.
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PACIFIC OCEAN Washington Oregon CaliforniaNevadaUtah Idaho
Montana Wyoming Yellowstone Caldera Chain Yellowstone National Park
Hot spot 0.8 Ma 2.0 1.8 4.3 10.3 6.6 6.2 11 12.5 13.8 14.715.6 16.1
13.7 15.5
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Yellowstone National Park Hot spot 0.8 Ma 2.0 1.8 4.3 10.3 6.6
6.2 11 12.5 13.8 14.715.6 16.1 13.7 15.5 The North American Plate
is moving southwest over the Yellowstone hot spot.
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10 things you didnt know about volcanoes (58:52) - Youtube
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Lithosphere Outer core Mantle Plume head Core-mantle boundary
Core-mantle boundary Instability at the core-mantle boundary causes
a mantle plume to arise. Flood basalts Basaltic magma penetrates
the lithosphere and erupts as flood basalts. Hot-spot volcano Plume
tail Plate movement The plume tail may form a hot-spot volcano.
Active volcano Active volcano Extinct volcano Extinct volcano
Continued plate movement creates a hot- spot volcano chain.