Crater – Lava collects in the crater, the bowl- shaped area that forms around the volcano’s vent. Volcano Menu Crater Vent Lava FlowPipe Magma chamber Side Vent
Vent – The point on the surface where magma and gas leave the volcano’s pipe. Volcano Menu Crater Vent Lava FlowPipe Magma chamber Side Vent
Pipe – A narrow, almost vertical crack in the crust through which magma rises to the surface. Volcano Menu Crater Vent Lava Flow Pipe Magma chamber Side Vent
Magma Chamber – A large underground pocket of magma that forms from magma rising to the surface. Volcano Menu Crater Vent Lava FlowPipe Magma chamber Side Vent
Lava Flow – The river of lava that pours down a volcano over the land. Volcano Menu Crater Vent Lava FlowPipe Magma chamber Side Vent
Types of Volcanic Eruptions – A volcano’s magma determines its volcanic cone and influences how the volcano erupts. – The silica content helps determine whether the volcanic eruption is quiet or explosive.
Shield Cones and Quiet Eruptions (Examples: Grimsvotn of Iceland and Kilauea of Hawaii) *Form as a result of sea-floor spreading or “hotspots” in the Earth’s mantle.
Shield Cones and Quiet Eruptions – Magma flows easily. – Dissolved gases in the magma bubble out easily. – Thin runny lava oozes from the vent and flows
Volcanic Hazards of Quiet Eruptions – Quiet Eruptions: Lava flows- set fire and bury everything in their path.
Composite Volcanoes and Explosive Eruptions (Examples: Mount Vesuvius of Italy and Mount Saint Helens Washington State) *Form as a result of subduction.
Volcanic Hazards – Time between eruptions for composite cones can span hundreds of years. (Dormant Volcano) – Example: Mt. St. Helens 123 years. – People may be unaware of the danger.
Explosive Eruptions Magma is thick and sticky. Thick magma builds up in the pipe, plugging it like a cork in a bottle. Pressure builds up due to the gases in the magma until the volcano explodes.
Volcanic Hazards of Explosive Eruptions – Lahar: A mud flow caused by melted snow. – Carries ash, trees and rocks.
Explosive Eruptions The gases push the magma out with incredible force. The explosion breaks lava into fragments that quickly cool and harden into different sizes.
Explosive Eruptions Fragments: – Volcanic Ash » fine, rocky, grain of sand sized particles. – Cinders- » pebble sized particles – Bombs- » large pieces of rock (baseball to the size of a car)
Explosive Eruptions Pyroclastic Flow – Occurs when an explosive eruption hurls out ash, cinders and bombs as well as gases. (400mph, 1,800˚F)