Volcanoes
They result from plate tectonics Volcanoes They result from plate tectonics The movement of plates or plate shifting Vents- openings in the Earth’s crust; magma exits
3 things they release Molten rock (magma) When it reaches the Earth’s surface it is called lava Ash Poisonous gases
Shield Volcano Composite Volcano Cinder Cone Volcano 3 types of Volcanoes Shield Volcano Composite Volcano Cinder Cone Volcano Depends on the type of eruption
Eruptions can happen several times Shield Volcanoes Largest volcanoes Mild eruptions Eruptions can happen several times
Shield Volcanoes magma Rich in iron Very fluid Can flow a great distance Produce gently sloping mountains
Where are they found? Hawaii Mauna Loa
Shield Volcanoes
Composite Volcanoes Made of alternating layers of: Ash Cinders Lava
Composite Volcanoes More violent eruptions
Composite Volcanoes Magma Rich in Silicates Thicker lava Gases are trapped in magma
Composite Volcanoes Because of gases This causes eruptions that alternated between flow and explosive activity Steeper slopes 1000’s of meter high
Examples Mount St. Helen Mount Fuji
Smallest & most abundant Violent eruptions Gases are trapped in magma Cinder Cone Volcanoes Smallest & most abundant Violent eruptions Gases are trapped in magma Larger amounts of gases
Hot ash and lava are thrown from the vent forming a cone. Cinder Cone Volcanoes Hot ash and lava are thrown from the vent forming a cone.
They are only active for a short period of time. Cinder Cone They are only active for a short period of time.
Cinder Cone
They are called seamounts Similar to Shield volcanoes Can occur under water They are called seamounts Similar to Shield volcanoes
Converging Boundaries Volcanoes occur at convergent Boundaries. Usually around the Pacific Ocean Ring of fire – 75% of all volcanoes are located on the Pacific Plate Boundary.
Convergent As ocean plates subduct: Magma rises and forms volcanoes
Divergent Boundaries Volcanoes can occur at divergent boundaries also. When plates move apart: Magma rises and fills in gaps Magma creates a volcanic mountain
Hot Spots Magma from deep inside the mantle rises to the surface This happens in the middle of plates This is called a hot spot This can form Islands
Chain of Islands Plates can move Hot Spots do not move This is how chains of islands are formed Hawaiian Islands