• Magma is a mixture of melted rock and hot gasses.
• Magma is a mixture of melted rock and hot gasses.
• Not all magma is the same:1. the kind of melted rock; and2. the amount of gas in the magma; make different types of magma.
• The amount of silica (quartz crystals) in the rock from which magma is made effects the viscosity or thickness.
• The amount of silica (quartz crystals) in the rock from which magma is made effects the viscosity or thickness.
• More silica (quartz) in the magma makes it thicker or higher viscosity.
• BASALTIC – made from oceanic crust and mantle material, so it has low silica content.
• BASALTIC – made from oceanic crust and mantle material, so it has low silica content.
• Low silica content means low viscosity, thinner magma.
• BASALTIC – made from oceanic crust and mantle material, so it has low silica content.
• Low silica content means low viscosity, thinner magma.
• Makes quiet volcanoes, like Hawaiian Islands, Iceland, Africa.
• GRANITIC – made from continental crust, so it has high silica content.
• GRANITIC – made from continental crust, so it has high silica content.
• High silica content means high viscosity, thicker magma.
• GRANITIC – made from continental crust, so it has high silica content.
• High silica content means high viscosity, thicker magma.
• Makes explosive volcanoes, like Mt. St. Helens, Vesuvius, Krakatau.
• The amount of water in the rock also determines whether a volcano is quiet or explosive.
• The amount of water in the rock also determines whether a volcano is quiet or explosive.
• More water in the rock makes it easier to melt.
• The amount of water in the rock also determines whether a volcano is quiet or explosive.
• More water in the rock makes it easier to melt.
• The water also turns to water vapor, which builds up as gas bubbles.
• MORE WATER, MORE GAS, BIGGER BLAST!
• MORE WATER, MORE GAS, BIGGER BLAST!
• How would you get more water in the rock?
• MORE WATER, MORE GAS, BIGGER BLAST!
• How would you get more water in the rock?
• In subduction zones, ocean water is also pulled down into the mantle with the plates.
• Most volcanoes are found at convergent plate boundaries.
• WHY?
• Most volcanoes are found at convergent plate boundaries.
• WHY?• Subduction pushes oceanic crust into
the mantle.
• Most volcanoes are found at convergent plate boundaries.
• WHY?• Subduction pushes oceanic crust into
the mantle.• The crust melts and rises back up to
make volcanoes.
• Volcanoes can also be found at divergent boundaries.
• Plates spread apart and lava oozes out.
• HOT SPOTS – extra hot plume of hot mantle material rises up from the core and melts the crust.
• Examples: Hawaii, Yellowstone
• MAGMA CHAMBER – pocket where magma collects.
• MAGMA CHAMBER – pocket where magma collects.
• VENT - opening in Earth’s crust where magma comes out.
• MAGMA CHAMBER – pocket where magma collects.
• VENT - opening in Earth’s crust where magma comes out.
• CRATER – bowl shaped pit around the main vent.
• MAGMA CHAMBER – pocket where magma collects.
• VENT - opening in Earth’s crust where magma comes out.
• CRATER – bowl shaped pit around the main vent.
• CALDERA – huge depression created when the magma chamber collapses.
• SHIELD VOLCANO: volcano with broad, gently sloping sides.
• SHIELD VOLCANO: volcano with broad, gently sloping sides.
• Quiet eruptions, basaltic lava, little gas.
• SHIELD VOLCANO: volcano with broad, gently sloping sides.
• Quiet eruptions, basaltic lava, little gas.• Largest volcanoes – found at hotspots
(Hawaii, Galapagos) and divergent boundaries (Iceland, East Africa).
• COMPOSITE VOLCANO: A volcano with steep sides formed by layers of thick lava, tephra (hot rocks), and ash.
• COMPOSITE VOLCANO: A volcano with steep sides formed by layers of thick lava, tephra (hot rocks), and ash.
• Usually have explosive eruptions, lots of gas, pyroclastic flows.
• COMPOSITE VOLCANO: A volcano with steep sides formed by layers of thick lava, tephra (hot rocks), and ash.
• Usually have explosive eruptions, lots of gas, pyroclastic flows.
• Found at convergent boundaries with subduction zones – Mt. St. Helens, Krakatoa, Mt. Fuji, Mt. Rainier, Vesuvius.
• CINDER CONE: small volcano with steep sides formed by tephra (hot rocks).
• CINDER CONE: small volcano with steep sides formed by tephra (hot rocks).
• Large volcanoes usually have small cinder cones on them, like pimples.
• A supervolcano is a volcano which is a thousand times bigger than any we have seen during recorded human history.
• A supervolcano is a volcano which is a thousand times bigger than any we have seen during recorded human history.
• Geologic evidence shows that many such eruptions have happened in Earth’s past, and will likely happen again.
• A supervolcano is a volcano which is a thousand times bigger than any we have seen during recorded human history.
• Geologic evidence shows that many such eruptions have happened in Earth’s past, and will likely happen again.
• These large eruptions can alter weather and climate and lead to extinction of species.
• At least two supervolcanoes are suspected of creating or causing mass extinctions:
• At least two supervolcanoes are suspected of creating or causing mass extinctions:
• SIBERIAN TRAPS – 250 million years ago. May have caused Permian extinction.
• At least two supervolcanoes are suspected of creating or causing mass extinctions:
• SIBERIAN TRAPS – 250 million years ago. May have caused Permian extinction.
• DECCAN TRAPS – 65 million years ago. Now suspected of killing off the dinosaurs.
• Last erupted about 74,000 years ago.
• Last erupted about 74,000 years ago.• 1,000 times bigger than Mt. St. Helens.
• Last erupted about 74,000 years ago.• 1,000 times bigger than Mt. St. Helens.• Caldera is 100 kilometers long and 30
kilometers wide.
• Last erupted about 74,000 years ago.• 1,000 times bigger than Mt. St. Helens.• Caldera is 100 kilometers long and 30
kilometers wide.• Eruption created “volcanic winter” – ash
and dust blown into the atmosphere blocks out the Sun.
• “Volcanic winter” kills plants, makes the Earth colder.
• 60% of the human population may have died as a result of this eruption.
• “Volcanic winter” kills plants, makes the Earth colder.
• 60% of the human population may have died as a result of this eruption.
• Last erupted 640,000 years ago.
• Last erupted 640,000 years ago.• Smaller than Lake Toba, caldera is 72 km
long and 55 km wide.
• Last erupted 640,000 years ago.• Smaller than Lake Toba, caldera is 72 km
long and 55 km wide.• Caused by North American plate moving
across a “hot spot” in Earth’s mantle.
• Last erupted 640,000 years ago.• Smaller than Lake Toba, caldera is 72 km
long and 55 km wide.• Caused by North American plate moving
across a “hot spot” in Earth’s mantle.• Supereruptions on this hot spot have
regularly occurred every 600,000 to 800,000 years.
• In recent years, Yellowstone has seen increases in earthquakes around the caldera.
• In recent years, Yellowstone has seen increases in earthquakes around the caldera.
• Ground has begun rising an average of 3 inches per year.
• In recent years, Yellowstone has seen increases in earthquakes around the caldera.
• Ground has begun rising an average of 3 inches per year.
• Is it getting ready to erupt?
• Supereruption would send 1000 cubic kilometers of ash into the air.
• Supereruption would send 1000 cubic kilometers of ash into the air.
• Ash would cover most the United States.
• Supereruption would send 1000 cubic kilometers of ash into the air.
• Ash would cover most the United States.
• Ash could be as much as 6 inches deep in the Salt Lake Valley.
• Supereruption would send 1000 cubic kilometers of ash into the air.
• Ash would cover most the United States.
• Ash could be as much as 6 inches deep in the Salt Lake Valley.
• Volcanic winter would effect climate in Utah and around the world.