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All the processes associated with the discharge of magma, hot fluids, ash, gases. Volcanoes are fueled by magma. Magma rises to the surface because it's less dense.
Volcanism
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Pluton that forms when magma intrudes parallel of layers of rock
Sills
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Lava flows out of cracks (fissures) in Earth's crust. Hot sports can also form floor basalts when they are not as explosive.
Ex. Columbian river basalts, Deccan Traps
Flood Basalts
Forms from continental crust that results in high silica and gas content.
Thick magma that results in large explosive erupting
VERY EXPLOSIVE
Rhyolitic Magma
Formed 16.7 million years ago
Located in NW USA
Volume of 170,000 km^3
Columbian River Basalts
Smallest of the 3 types of volcanoes
Steep- sloped, cone shaped
Usually made of fragments of basaltic lava(scoria)
Explosive eruptions
Usually form at the edges of larger volcanoes
Smallest
Cinder Cones
A group of intrusive igneous rock bodies that form as magma moves into solid crust layers. They are coarse grained because the magma solidified slowly
Plutons
Rapidly moving flows of tephra mixed with extremely hot, suffocating gases
Pyroclastic Flows
Crust seperates allowing magma to ruse to the surface. Forms "pillows" when it erupts called pillow lava. 2/3rds of earths volcanism occurs underwater along these plates.
Only Underwater
Divergent Volcanism
Force overlying rock apart and form fissures
Cause blocks to break off and sink into magma
Melt into rock (where they are already fissures)
3 ways lava interacts with the crust
Large irregularly shaped masses of coarse grained igneous rock that covers at least 100 square kilometers and take millions of years to form
Batholiths
Most volcanoes on land result from oceanic-continental subduction. Plates are colliding and causing plates to undergo subduction. The oceanic plate subducts bringing H20. Magma rises= volcano
VERY EXPLOSIVE
Convergent Volcanism
Low viscosity ( low silica) magma that flows from deep inside the earth to the surface
gentle eruptions
runny
Basaltic Magma
Much larger than cinder cones
Tall, majestic mountains
Made of layers of rock and ash
Cycles through quiet and explosive eruptions
Ex. Mount St. Helens (Washington)
WORLD CHANGING MOST EXPLOSIVE
Composite Volcano
Largest of the types of volcanoes
Long gentle slopes
Made of layers of solidified basaltic lava
Quiet eruptions
Ex. Mauna Loa in Hawaii
BIGGEST
Shield Volcanoes
Formed from the subduction of oceanic crust which created a moderate viscosity due to higher silica content
sometimes has explosive eruptions
mid viscosity
Andesitic Magma
Lava and rock that erupted into the air
volcanic neck is a dike that forms when the magma in a volcanic conduit solidifies
horizontal sill
dikes
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Unusually hot regions of earths mantle where high-tempature plumes of magma ruse to the surface. As the plate moves, new volcanoes form. The magma melts through the crust and forms new volcanoes.
Ex. Hawaiian Islands
Hot Spots
Lens shaped pluton with a round top and a flat bottom
formed when magma intrudes into parallel rock layers close to the surface of the earth and rock bow upwards from the pressure that can form a laccolith
Laccolith
As the amount of gases in magma increases the magmas explosivity also increases
Common gases: Water vapor, carbon dioxide, sulfur dioxide, and hydrogen sulfide
More gas- bigger more violent volcano
Less gas- Less explosive smaller explosion
Composition gases
Formed 65 million years ago
Located in India
Volume of 512,000 km^3
Some geologists think the eruption of the deccan trap caused global change in the climate
Deccan Traps