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Volcanoes Chapter 6. 6.1 Volcanoes and Plate Tectonics Volcanoes from along _________________ – Both __________________________ Divergent: – Plates _______.

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Presentation on theme: "Volcanoes Chapter 6. 6.1 Volcanoes and Plate Tectonics Volcanoes from along _________________ – Both __________________________ Divergent: – Plates _______."— Presentation transcript:

1 Volcanoes Chapter 6

2 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

3 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

4 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

5 6.2 Volcanic EruptionsVolcanic Eruptions magma chamber lava flow side vent vent pipe crater

6 6.2 Volcanic Eruptions 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 1._______________ 2._______________ Magma expand and bubble Quiet Explosive falls increase pushes magma up

7 6.2 Volcanic Eruptions Quiet Volcanic Eruptions Quiet – Magma is _______________ – Gases bubble gently – Lava oozes quietly and ______________________ – 2 types of lava produced and form 2 types of rock: 1._________________ forms from lava that is fast- moving, thin, and runny. Looks like ropelike coils 2._________ forms form cooler, thicker lava. Has a rough texture with jagged chunks of lava low in silica can flow many kilometers Pahoehoe Aa

8 6.2 Volcanic Eruptions Explosive Volcanic Eruptions Explosive – 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 pressure trapped behind volcanic ash cinders bombs

9 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

10 6.2 Volcanic Eruptions Stages of activity: 1.Active (___________): – erupting or will erupt in the near future 2.Dormant (_____________): – Expected to become active in the future 3.Extinct (_________): – Unlikely to ever erupt again live sleeping dead

11 6.3 Volcanic Landforms Landforms from Lava and Ash: – ________________ – ___________________ – _________________ Other Landforms: – ______________ Huge holes left from a volcano that has collapsed Calderas Shield volcanoes Cinder cone volcanoes Composite volcanoes Lava plateaus

12 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

13 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

14 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

15 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

16 6.3 Volcanic Landforms Landforms from Magma: – ________________ Volcanic necks Dikes and sills Dome mountains Batholiths

17 6.3 Volcanic Landforms Volcanic Necks – Forms from ___________________ in the pipe of a volcano and then the surrounding rock wears away magma that hardens

18 6.3 Volcanic Landforms Dikes – Magma forces itself ___________________ and then hardens Sills – Magma squeezes ____________________ rock layers and hardens across rock layers between horizontal

19 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

20 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

21 Volcanic Eruptions

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