Volcanoes Chapter 6

6.1 Volcanoes and Plate Tectonics Volcanoes from along _________________ Both __________________________ Divergent: Plates _______ and allow magma to reach surface Convergent: One plate ______________________ __________ is brought down with the plate and eventually forms magma that rises to the surface plate boundaries divergent and convergent fracture sinks under the other Water

6.1 Volcanoes and Plate Tectonics Island arcs Result of ____________________ _______________ plate subducts into deep ocean trench Water in the sinking plate leaves and causes ____________________________________ Magma ______________________ ocean floor to form volcano These volcanoes form ___________________ convergent boundary Older, denser the mantle to melt and form magma rises and breaks through a string of islands

6.1 Volcanoes and Plate Tectonics Hot Spots Hot spots _______________________ for millions of years while the earth’s plates move over them Some lie close to plate boundaries and some are ____________________ ________________ formed from a plate moving over a hotspot remain in the same place in the middle of plates Hawaiian islands

6.2 Volcanic Eruptions crater vent side vent pipe lava flow magma chamber

6.2 Volcanic Eruptions Eruptions: Two types of eruptions ____________ rises to surface Dissolved gases in magma ___________________ Pressure in magma __________ and size of bubbles ____________ Force of expanding gases __________________ the volcano to the surface Two types of eruptions _______________ Magma expand and bubble falls increase pushes magma up Quiet Explosive

6.2 Volcanic Eruptions Quiet Volcanic Eruptions Magma is _______________ Gases bubble gently Lava oozes quietly and ______________________ 2 types of lava produced and form 2 types of rock: _________________ forms from lava that is fast-moving, thin, and runny. Looks like ropelike coils _________ forms form cooler, thicker lava. Has a rough texture with jagged chunks of lava low in silica can flow many kilometers Pahoehoe Aa

6.2 Volcanic Eruptions Explosive Volcanic Eruptions Magma is _________________, thick, and sticky Magma blocks the volcano pipe like a cork Gases are _______________the magma and build up ____________ until the force is great enough to push the magma out volcano Throws lava in the air that cools Smallest pieces are called _________________ Pebble-sized pieces are ________________ Larger pieces that range from gold ball to car size are called ______________ high in silica trapped behind pressure volcanic ash cinders bombs

6.2 Volcanic Eruptions Volcano Hazards __________________ cause fires and can bury everything in their path Explosive eruptions send out hot rock and ash, and __________________ Explosive eruptions can also cause ____________ of mud, rock, and melted snow Quiet eruptions pyroclastic flow landslides

6.2 Volcanic Eruptions Stages of activity: Active (___________): erupting or will erupt in the near future Dormant (_____________): Expected to become active in the future Extinct (_________): Unlikely to ever erupt again live sleeping dead

6.3 Volcanic Landforms Landforms from Lava and Ash: Other Landforms: ________________ ___________________ _________________ Other Landforms: ______________ Huge holes left from a volcano that has collapsed Shield volcanoes Cinder cone volcanoes Composite volcanoes Lava plateaus Calderas

6.3 Volcanic Landforms Cinder Cone Volcanoes Formed from ____________________with magma that had high silica content Ash, cinders, and bombs ____________________ in a steep, cone-shaped hill or mountain an explosive volcano build up around the vent

6.3 Volcanic Landforms Composite Volcanoes ________________________ Eruptions alternate between _____________ and explosive with ash, cinders, and bombs Tall, cone-shaped mountain with layers that alternate with _______________ Can be more than ___________________________ The silica content varies lava flows lava and ash 4,800 meters tall

6.3 Volcanic Landforms Shield Volcanoes Thin layers of lava come out of a ________ The lava hardens on top of previous layers Wide, gently sloping mountain ____________________ on the ocean floor are usually formed this way vent Hot spot volcanoes

6.3 Volcanic Landforms Lava Plateaus Lava flows from several cracks in the earth’s crust Lava is ___________________ so it travels far before it cools and solidifies ________________ with this type of lava flow form high, level plateaus thin and runny Millions of years

6.3 Volcanic Landforms Landforms from Magma: ________________ Volcanic necks Dikes and sills Dome mountains Batholiths

6.3 Volcanic Landforms Volcanic Necks Forms from ___________________ in the pipe of a volcano and then the surrounding rock wears away magma that hardens

6.3 Volcanic Landforms Dikes Sills Magma forces itself ___________________ and then hardens Sills Magma squeezes ____________________ rock layers and hardens across rock layers between horizontal

6.3 Volcanic Landforms Dome Mountains Forms when a large body of hardened magma is __________________________________ The magma forces rock layer to ____________ into a dome shape Rock above the dome mountain wears away, leaving the hardened magma exposed pushed towards the Earth’s surface bend upward

6.3 Volcanic Landforms Batholiths A mass of rock formed by a large _________________ cooled inside the crust Millions of years or weathering and erosion wear away the ____________________ and the batholith moves upward _______________ carve the batholith into a mountain body of magma overlying rock Ice and water

Volcanic Eruptions