Intro to volcanoes module


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Provided to the METSAT Element of the Weather Intelligence flight, to help the analysts get a better understanding of volcanoes.

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Intro to volcanoes module

  1. 1. Volcano A naturally occurring opening in the surface of the Earth through which molten, gaseous, and solid material is ejected. ~Encarta EXPLORE CHAPTERS Introduction Etymology Plate Tectonics & Hotspots Types of Volcanoes Lava Composition Lava Behavior Types of Eruptions Ring of Fire 2009 AFWA Issued volcano products Navigation: Use the arrows at the bottom of the screen to move to the next, previous, home windows, otherwise click on the hyperlink to jump to more information. Look for images in the upper left corner to jump to more in depth explanation of what is on that page. HOME
  2. 2. IntroductionIntroduction As a METSAT analyst, it is your job to explore all available information tools to help determine the location of a volcanic eruption of ash and the extent of the height and direction of where the ash will travel. *It is important to note that while it is important to observe where lava is flowing, advisory products will only be issued HOME
  3. 3. HOME Make note of everything that can eject from a volcano and think about how each can impact the local population and aircraft flying near or through the eruption cloud. INTRODUCTION
  4. 4. EtymologyEtymology • The word volcano is derived from the name of Volcano, a volcanic island in the Aeolian Islands of Italy whose name in turn originates from Vulcan, the name of a god of fire in Roman mythology. • The study of volcanoes is called volcanology. HOME
  5. 5. Plate Tectonics & Hotspots HOME Divergent plate boundaries Convergent plate boundaries Hotspots The pulling apart of plates, causing molten rock to come to the top of the mantle. Causes mainly submarine volcanic activity and creates new oceanic crust. The collision of plates, causing Subduction or one plate to submerge beneath the other. Located away from tectonic plates, over mantle plumes where pipes vent magma. Volcanoes formed over hotspot go dormant and new ones are formed when plates move overhead.
  6. 6. Divergent Plate Boundaries Most divergent plate boundaries are at the bottom of the oceans, causing most of the volcanic activity to be submarine, thus forming new seafloor. HOME PLATE TECTONICS
  7. 7. Convergent Plate Boundaries HOME When two plates (usually an oceanic and continental plate) collide, causing the one plate to submerge under the other plate (called subducting). In the case of oceanic-continental, a deep trench just off shore is formed. When the viscous magma, high in silica content, reaches the surface, a volcano is formed. *This is what caused the typical Ring of Fire volcanoes.* Oceanic - Oceanic convergenceContinental - Continental convergenceOceanic - Continental convergence PLATE TECTONICS
  8. 8. How Plate Tectonics Work 1 – Lithosphere: Continental & Oceanic 2 – Asthenosphere 3 – Softened, dense rock flows slowly 4 – Convection currents bring hot material up toward the surface 5 – Convection currents diverge at base of lithosphere; pulls on the solid plate. Tension causes solid plate to break apart (divergent plate boundary) 6 – Space fills with molten rock (magma). Seawater cools magma and solidifies, forming new oceanic lithosphere. Over time mid-ocean ridge gets larger. 7 - The older part of plate moves away from the ridge, where the new lithosphere has been added. 8 – The further away the plate moves from the spreading ridge, it cools. The colder the plate, the heavier it becomes. The furthest edge from the ridge becomes denser than asthenosphere beneath it. HOME PLATE TECTONICS
  9. 9. How Plate Tectonics Work Cont’d 9 – The dense plate sinks beneath another, causing a subduction zone to form. 10 – The sinking edge pulls the rest of the plate behind it. 11 – Subduction zones are a form of convergent plate boundary. The less dense continental plate floats above the more dense asthenosphere. 12 – Extreme heat and pressure at depth of the subducting plate cause fluids to sweat, which percolate upward and melts overlying solid mantle above the plate to form pockets of magma. 13 – The new magma is less dense than surrounding rock and rises toward surface. It cools and solidifies as large intrusive rocks. When exposed by erosion, forms the cores of great mountain ranges (i.e. Sierra Nevada & Andes) 14 – Some molten rock reaches Earth’s surface to erupt , forming volcanic rocks. Accumulation of layers over time construct volcanic mountain ranges (i.e. Cascade range) HOME PLATE TECTONICS
  10. 10. Hotspots Located over a mantle plume, where the convection of the Earth’s mantle creates a column of hot material that rises until it reaches the crust. Pipes form in the crust, which vents magma. HOME PLATE TECTONICS
  11. 11. Ring of Fire Result of plate tectonics and the movement and collisions of crustal plates. Area where large numbers of earthquakes and volcanic eruptions occur in a 40,000km horseshoe shape. Associated with a nearly continuous series of activity. Contains 452 volcanoes, with over 75% of worlds active and dormant volcanoes. HOME PLATE TECTONICS
  12. 12. 4 Main Types of Volcanoes4 Main Types of Volcanoes Cinder Cones (Volcanic cones) Composite volcanoes (Stratovolcanoes) Shield Volcanoes Lava domes HOME
  13. 13. Shield Volcanoes • Named for their broad, shield-like profiles. • Formed by the eruption of low-viscosity lava that can flow a great distance from a vent, but usually not a catastrophic explosion. • Gradual buildup and near continuous characteristics. • More common in oceanic settings. VOLCANO TYPES HOME
  14. 14. Lava Domes • Formed by small, bulbous masses of lava too viscous to flow a great distance. • Lava piles over and around its vent, and the dome grows by expansion within. • Commonly found within craters or on flanks of large composite volcanoes. HOME VOLCANO TYPES
  15. 15. Volcanic (Cinder) Cones • Built from particles of congealed lava ejected from a single vent. • Gas-charged lava blows violently into the air, breaks into small fragments and fall once solid as cinders around the vent. • Most have a bowl-shaped crater at the summit, and rarely rise more than 1K feet above surroundings. HOME VOLCANO TYPES
  16. 16. Stratovolcanoes (Composites) • Steep-sided, symmetrical cones. Formed by alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs. • May rise 8K or more feet above surroundings. HOME VOLCANO TYPES
  17. 17. Supervolcanoes • Occurs when magma in the Earth rises into the crust from a hotspot but cannot break through the crust. Pressure builds until the crust can no longer contain it. • Can produce devastation on an enormous scale. • Most dangerous kind and can cool global temperatures for years after eruptions due to the volume of sulfur and ash. HOME VOLCANO TYPES
  18. 18. Submarine volcanoes • Located on the ocean floor. • Active ones in shallow water may shoot steam and rocky debris into the air. • Deep eruptions may be prevented by the weight of the water. • Rapid cooling by the water causes the erupted materials to solidify, often creating pillow lava. • That is how many islands were developed. HOME VOLCANO TYPES
  19. 19. Subglacial volcanoes (glaciovolcano) • Develop under icecaps. • During an eruption, the heat of the lava melts the overlying ice. The water cools the lava, creating pillow lava shapes. • Most common in Iceland & Antarctica and have a flat top with steep sides. HOME VOLCANO TYPES
  20. 20. Lava CompositionLava Composition Oxygen (O) Silicon (Si) Aluminum (Al) Iron (Fe) Magnesium (Mg) Titanium (Ti) Calcium (Ca) Sodium (Na) Potassium (K) Phosphorous (P) HOME 10 elements make up most magmas: O & Si are the two most abundant elements in magma and are therefore described by silica content (SiO2). Click on the types of lava below for more information on each.
  21. 21. Felsic • High percentage of silica (>63%) • Highly viscous • Erupted as domes or short, stubby flows. • Typically forms stratovolcanoes or lava domes. • The viscosity traps gases, which cause more catastrophic eruptions . • Spurs pyroclastic flows and leaves thick layers of deposits, sometimes several meters deep. LAVA COMPOSITION HOME
  22. 22. Pyroclastic flows • Temperatures as high as 1,200 ⁰C • Will incinerate anything flammable in their path, while leaving a thick layer of pyroclastic flow deposit. LAVA COMPOSITION HOME
  23. 23. Andesitic • Lower in aluminum and silica, usually richer in magnesium and iron. • Form andesite domes and block lavas. • Temperatures between 750 and 950 ⁰C and are less viscous. LAVA COMPOSITION HOME
  24. 24. Mafic • Erupt at temperatures above 950 ⁰C. • High in iron and magnesium, with lower aluminum and silica. • Low viscosities. • Typically forms low- profile shield volcanoes. LAVA COMPOSITION HOME
  25. 25. Lava BehaviorLava Behavior Highly viscous • Flows slowly, clogs, and forms semi-solid blocks which resist flow. • Tends to entrap gas, which forms bubbles within the rock. • Correlates to explosive eruptions and is associated with pyroclastic flows. Low viscous • Tends to flow easily, forming puddles, channels and rivers of molten rock. • Tends to easily release bubbling gases as they’re formed. • Rarely pyroclastic. • Tend to form broad shields rather than steep cones. Viscosity of lava determines how the lava will behave. HOME
  26. 26. Types of EruptionsTypes of Eruptions Non-explosive • Flood lavas • Hawaiian style • Mid-ocean ridges Explosive • Strombolian • Vulcanian • Surtseyan • Vesuvian/Plinian • Peléan • Bandaian HOME
  27. 27. Non-explosive • Flood lavas: basaltic & can be highly voluminous • Hawaiian style: with some tephra and fast- moving fluid lavas; often channelized. • Mid-ocean ridges: largely restricted to spreading center rifts as small cones and sheet flows. HOME ERUPTION TYPES
  28. 28. Explosive  Strombolian • Low-level eruptions, consists of ejection of incandescent cinder, lapilli and lava bombs to altitudes of tens to hundreds of meters. • Small to medium in volume, with sporadic violence. 1 – Ash plume 2 – Lapilli 3 – Volcanic ash rain 4 – Lava fountain 5 – Volcanic bomb 6 – Lava flow 7 – Layers of lava and ash 8 – Stratum 9 – Dike 10 – Magma conduit 11 – Magma chamber 12 - Dike HOME ERUPTION TYPES
  29. 29. Explosive  Vulcanian • Eruption characterized by a dense cloud of ash-laden gas exploding from the crater and rising high above the peak. • Increased silica content of magma (which has increased viscosity) means increased explosiveness. 1 – Ash plume 2 – Lapilli 3 – Lava fountain 4 – Volcanic ash rain 5 – Volcanic bomb 6 – Lava flow 7 – Layers of lava and ash 8 – Stratum 9 – Sill 10 – Magma conduit 11 – Magma chamber 12 - Dike Sakurajima, Japan HOME ERUPTION TYPES
  30. 30. Explosive  Surtseyan • Takes place in shallow seas or lakes. • Commonly phreatomagmatic (a result of interaction between water and magma) representing violent explosions. 1 – Water vapor cloud 2 – Cupressoid ash 3 – Crater 4 – Water 5 – Layers of lava and ash 6 – Stratum 7 – Magma conduit 8 – Magma chamber 9 – Dike HOME ERUPTION TYPES
  31. 31. Explosive  Vesuvian/Plinian • Displays as columns of gas and volcanic ash extending high into the stratosphere and eject large amounts of pumice. • Can last less than a day to months. May collapse top of volcano, resulting in a caldera, and fine ash will deposit over large areas. HOME Redoubt ERUPTION TYPES
  32. 32. Explosive  Peléan • Characteristics include presence of a glowing avalanche of hot volcanic ash and formation of lava domes, short flows of ash or the creation of pumice cones. • Collapse of ash columns. HOME 1 – Ash plume 2 – Volcanic ash rain 3 – Lava dome 4 – Volcanic bomb 5 – Pyroclastic flow 6 – Layers of lava and ash 7 – Strata 8 – Magma conduit 9 – Magma chamber 10 – Dike ERUPTION TYPES
  33. 33. Classification of volcanoes • Volcanoes that erupt regularly. • Actual lifespan can last from months to several million years. Dormant • Volcanoes that have erupted in historical times, but now quiet. • Considered when eruptions have been historically many (possibly thousands or more) years apart and could erupt again. (Pompeii and previously Soufriere Hills) Active Extinct • Volcanoes that have not erupted in recorded historical times • Scientists consider them to be unlikely to erupt again because there is no longer a lava supply. ERUPTION TYPES HOME
  34. 34. 2009 AFWA Issued2009 AFWA Issued HOME
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