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Volcanoes Volcanology: The study of volcanoes Vulcanologists: scientists who study volcanoes.

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Presentation on theme: "Volcanoes Volcanology: The study of volcanoes Vulcanologists: scientists who study volcanoes."— Presentation transcript:

1 Volcanoes Volcanology: The study of volcanoes Vulcanologists: scientists who study volcanoes

2 Anatomy of a Volcano Central vent: where major eruption occurs Central vent: where major eruption occurs Flank vent: secondary vent Flank vent: secondary vent Magma chamber: where magma stays until pressure forces it up the vent Magma chamber: where magma stays until pressure forces it up the vent Fumarole: flank vent that releases gas only Fumarole: flank vent that releases gas only

3 A. Magma and Lava Volcanism: any activity that includes the movement of magma towards or on the Earth's surface Volcanism: any activity that includes the movement of magma towards or on the Earth's surface

4 Magma Magma: liquid rock - volcanic rock found below the Earth's surface; solid rock can become magma when liquid (water) is added (subduction zones) Magma: liquid rock - volcanic rock found below the Earth's surface; solid rock can become magma when liquid (water) is added (subduction zones)

5 Lava : magma that erupts onto the Earth's surface Magma can flow onto Earth's surface through an opening - vent - or crack - fissure A volcano is any structure formed on Earth's surface by the vent and volcanic material that builds up around it

6 B. Major Volcano Zones 1. Subduction zones – 1. Subduction zones – a. oceanic lithosphere melts as it plunges beneath the continental plate, water added to mantle material creates magma ex. Ring of Fire b. ocean trenches where oceanic subducts under oceanic creates volcanic islands arcs ex. Aleutian Islands, AK, Japan

7 2. Mid-ocean ridges 2. Mid-ocean ridges magma flows up through rift zone, can form underwater volcanoes ex. Iceland - MOR above sea-level; contains many fissures

8 3. Hot spots - in the middle of a plate is a spot where magma flows upward; plate moves over the hot spot and form a volcano; volcano is carried away by plate and become extinct 3. Hot spots - in the middle of a plate is a spot where magma flows upward; plate moves over the hot spot and form a volcano; volcano is carried away by plate and become extinct ex. Hawaiian Islands A new Hawaiian island forming underwater - Loihi A new Hawaiian island forming underwater - Loihi

9 C. Types of Lava The violence of an eruption depends on : The violence of an eruption depends on : type of magma (minerals) temperature of the magma The amount of dissolved gases

10 Viscosity viscosity - resistance to flow viscosity - resistance to flow More viscous - flows slowly More viscous - flows slowly Less viscous - flows quickly Less viscous - flows quickly

11 Mafic Lava Dark colored Dark colored Contains magnesium and iron Contains magnesium and iron Makes up oceanic crust Makes up oceanic crust Is hot and thin, less viscous - flows quickly - gases escape easily - "quiet flow" Is hot and thin, less viscous - flows quickly - gases escape easily - "quiet flow" ex. Hawaiian volcanoes ex. Hawaiian volcanoes

12 Pahoehoe If mafic lava cools slowly: forms wrinkly crust - pahoehoe - Hawaiian for "ropy" If mafic lava cools slowly: forms wrinkly crust - pahoehoe - Hawaiian for "ropy"

13 Aa if it cools quickly: it forms rough, jagged chunks - aa if it cools quickly: it forms rough, jagged chunks - aa

14 Lava Tubes If outer edges cool quickly and inner lava still flows: creates tunnel called lava tubes If outer edges cool quickly and inner lava still flows: creates tunnel called lava tubes

15 Pillow Lava Lava flowing out of fissures on ocean floor: cools quickly & forms rounded pillow lava Lava flowing out of fissures on ocean floor: cools quickly & forms rounded pillow lava

16 Felsic Lava Is light colored Is light colored Contains silica Contains silica Makes up continental crust Makes up continental crust Is cool and thick, more viscous - lots of trapped gases - explosive! Is cool and thick, more viscous - lots of trapped gases - explosive! ex. continental volcanoes - Mt. St. Helens ex. continental volcanoes - Mt. St. Helens

17 D. Pyroclastic material These are rock fragments sent into the air from explosive felsic lava eruptions These are rock fragments sent into the air from explosive felsic lava eruptions They are described by size They are described by size

18 Volcanic Dust and Ash Volcanic dust< 0.25 mm in diameter Volcanic dust< 0.25 mm in diameter Volcanic ash> mm Volcanic ash> mm These may travel far from the eruption!! These may travel far from the eruption!!

19 Lapilli, Bombs and Blocks Lapilli "little stones“ Lapilli "little stones“ mm; they fall near the vent Volcanic bombs - clumps of lava sent spinning thru the air Volcanic bombs - clumps of lava sent spinning thru the air Volcanic blocks - large rocks blasted from fissure; can be house-size Volcanic blocks - large rocks blasted from fissure; can be house-size

20 Pyroclastic flow The most deadly aspect to volcanic eruptions The most deadly aspect to volcanic eruptions Combination of hot, toxic gases coming from vents, up to 1000 C, and 750 km/hr Combination of hot, toxic gases coming from vents, up to 1000 C, and 750 km/hr More dense than air, so rolls into villages killing victims quickly (e.g. Pompeii) More dense than air, so rolls into villages killing victims quickly (e.g. Pompeii) Video: Video:

21 E. Volcano Types how do volcanoes form? assignment-discovery-formation-of-volcanoes-video.htm assignment-discovery-formation-of-volcanoes-video.htm assignment-discovery-formation-of-volcanoes-video.htm

22 1. Shield Volcanoes Form: when hot, mafic lava builds up around the vent - form cones Form: when hot, mafic lava builds up around the vent - form cones Have wide, broad bases and gently sloping sides, medium height Have wide, broad bases and gently sloping sides, medium height ex. Hawaiian Islands ex. Hawaiian Islands

23 2. Cinder Cone Volcanoes Very steep sloped sides, short (few hundred meters) Very steep sloped sides, short (few hundred meters) Formed from layers of ash and other explosive pyroclastic materials Formed from layers of ash and other explosive pyroclastic materials ex. Sunset Crater, AZ ex. Sunset Crater, AZ

24 3. Composite Volcanoes, or Stratovoclanoes Composite means a mix of unlike things, “strato-” means layer Composite means a mix of unlike things, “strato-” means layer Formed from alternating layers of lava and ash Formed from alternating layers of lava and ash ex. Mt. Fuji, Mount Hood, Mt. St. Helens ex. Mt. Fuji, Mount Hood, Mt. St. Helens

25 Crater A pit at top of volcano, formed when material is blown out A pit at top of volcano, formed when material is blown out Usually widens due to weathering and erosion Usually widens due to weathering and erosion Often a smaller cone may form inside crater Often a smaller cone may form inside crater When filled with water = a crater lake - Crater Lake National Park, Oregon When filled with water = a crater lake - Crater Lake National Park, Oregon

26 Caldera A large, basin shaped depression formed from a crater A large, basin shaped depression formed from a crater If magma chamber is empty, the crater collapses - forms caldera If magma chamber is empty, the crater collapses - forms caldera Also formed from huge eruptions Also formed from huge eruptions ex. Krakatau ex. Krakatau

27 F. Predicting Volcanic Eruptions Scientists use the following to predict EQs: 1. seismographs monitor for small EQs from growing pressure, that often precede eruptions 2. slight bulging of surface from magma pushing out 3. change in ground tilt

28 4. gases 4. gases 5. history of previous eruptions 5. history of previous eruptions Very few volcanoes have a lengthy history to study; constant monitoring is required Very few volcanoes have a lengthy history to study; constant monitoring is required

29 G. Extraterrestrial Volcanoes Moon - was once volcanically active - evidence of lava flows Moon - was once volcanically active - evidence of lava flows Craters - a result of bombardment by meteorites) Craters - a result of bombardment by meteorites)

30 Mars - many volcanoes and volcanic features Mars - many volcanoes and volcanic features Olympic Mons - shield volcano - 28 km above surface, base = 600 km; probably stayed on lava source for millions years (no plate tectonics) Olympic Mons - shield volcano - 28 km above surface, base = 600 km; probably stayed on lava source for millions years (no plate tectonics) Still active volcanoes on Mars?? Not sure, but it is seismically active Still active volcanoes on Mars?? Not sure, but it is seismically active

31 Io Moon of Jupiter Moon of Jupiter Many active volcanoes - more eruptions; more material ejected than on Earth each month; probably sulfuric lava Many active volcanoes - more eruptions; more material ejected than on Earth each month; probably sulfuric lava Spectacular eruptions - umbrella-shaped plumes hundreds km high Spectacular eruptions - umbrella-shaped plumes hundreds km high Vulcanism probably caused by friction Vulcanism probably caused by friction

32 Importance of Volcanoes all original rocks on Earth's crust were formed from cooled magma and/or lava all original rocks on Earth's crust were formed from cooled magma and/or lava water vapor from volcanoes early in Earth's history may have formed oceans water vapor from volcanoes early in Earth's history may have formed oceans gases from early eruptions formed the atmosphere gases from early eruptions formed the atmosphere volcanism adds new crust and reshapes planet each year volcanism adds new crust and reshapes planet each year

33 Supervolcanoes What are they? What are they? Several on youtube.com ex: under Yellowstone National Park ex: under Yellowstone National Park

34 Tsunami and landslides Alaska: Alaska: Volcano driven: East coast US (when ?) Volcano driven: East coast US (when ?) 10 ways the Earth will end10 ways the Earth will end: 10 ways the Earth will end


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