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VOLCANOES

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VOLCANOES

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    1. VOLCANOES

    2. VOLCANIC STRUCTURE Magma rises from magma chamber (storage area for lava) , forced up a narrow vent to crater by an increase in pressure. Gas, steam, and ash are released from the crater as volcanic bombs or a gentle flow. Pyroclastic flows may race down or magma may be released through secondary cones. Dykes and sills are formed when magma is pushed through preexisting rock.Magma rises from magma chamber (storage area for lava) , forced up a narrow vent to crater by an increase in pressure. Gas, steam, and ash are released from the crater as volcanic bombs or a gentle flow. Pyroclastic flows may race down or magma may be released through secondary cones. Dykes and sills are formed when magma is pushed through preexisting rock.

    3. VISCOSITY Temperature and composition (silica content) determine the viscosity of magma/lava Types of lava: - fluid - viscous All magma contains gases that expand and rise buoyantly as the magma rises to the surface (like bubbles in a soda)All magma contains gases that expand and rise buoyantly as the magma rises to the surface (like bubbles in a soda)

    4. FLUID LAVA Gases bubble away Occurs at higher temperatures Low silica content Erupts quietly Great (copious) flows of lava that build gently sloping volcanoes Ex. shield volcanoes All magma contains gases that expand and rise buoyantly as the magma rises to the surface (like bubbles in a soda)All magma contains gases that expand and rise buoyantly as the magma rises to the surface (like bubbles in a soda)

    5. VISCOUS LAVA Gases are trapped ? pressure builds ? erupts violently ? scattering volcanic fragments & ash widely Occurs at cooler temperatures High silica content Low flow forming steep-sided volcanoes Ex. Stratovolcanoes or composite volcanoes All magma contains gases that expand and rise buoyantly as the magma rises to the surface (like bubbles in a soda)All magma contains gases that expand and rise buoyantly as the magma rises to the surface (like bubbles in a soda)

    6. TYPES OF VOLCANOES Composite volcano (stratovolcanoes): Formed by alternating levels of ash, cinder, and lava Violent eruptions Steeper incline especially near crater Ex: Mt. Rainer, Mt. Vesuvius Shield volcano: Formed from fluid lava Many side vents Typically found over hot spots Ex: Mauna Loa These are the three main types, but there are other types as well on next picture.These are the three main types, but there are other types as well on next picture.

    8. TYPES OF VOLCANOES Fissures- formed from cracks in the Earth’s surface at divergent plate boundaries or near mid-ocean ridges. Dome volcano: steep, convex slope from thick fast cooling lava Caldera: older volcano with a large crater and many new little craters are formed, depressions formed by collapsed volcanoes (Crater Lake & Yellowstone) Fissures- formed from cracks in the Earth’s surface at divergent plate boundaries or near mid-ocean ridges. Dome volcano: steep, convex slope from thick fast cooling lava Caldera: older volcano with a large crater and many new little craters are formed, depressions formed by collapsed volcanoes (Crater Lake & Yellowstone)

    9. TYPES OF ERUPTIONS All of the above eruptions are named after the location of that volcano… Hawaii- Hawaiian islands, Stromboli (Italy), Vulcano (Italy), Mt. Peele (West Indies), and Plinian (The Pompeii explosion of Mount Vesuvius) Effusive- Hawaiian Islands Strombolian- viscous, sputtering of lava and gases Violent: Vulcanian Pelean- give warning signs a couple weeks prior All of the above eruptions are named after the location of that volcano… Hawaii- Hawaiian islands, Stromboli (Italy), Vulcano (Italy), Mt. Peele (West Indies), and Plinian (The Pompeii explosion of Mount Vesuvius) Effusive- Hawaiian Islands Strombolian- viscous, sputtering of lava and gases Violent: Vulcanian Pelean- give warning signs a couple weeks prior

    10. VOLCANOES ON LAND Silica-rich granitic (upper crustal rock) ? melts at subduction zones ? violent volcanic eruptions Ex. Mt. St. Helens

    11. VOLCANIC HOT SPOTS occurs in chains As the plate moves away from the heat source, volcano formation stops Older volcanoes farther away from heat source All magma contains gases that expand and rise buoyantly as the magma rises to the surface (like bubbles in a soda)All magma contains gases that expand and rise buoyantly as the magma rises to the surface (like bubbles in a soda)

    12. VOLCANIC HOT SPOTS

    13. RING OF FIRE Ring of fire- volcanoes around the pacific ocean like those that formed the Aleutian islands, the cascades (inc. Mt. Rainer), or Mt. Helens (WA-1980). Ring of fire- volcanoes around the pacific ocean like those that formed the Aleutian islands, the cascades (inc. Mt. Rainer), or Mt. Helens (WA-1980).

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