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MONDAY NOVEMBER 7, 2011

MONDAY NOVEMBER 7, 2011. HI guys ! – please give the substitute your attention and respect. Any names recorded will have ASD Thursday Today you have bell work, notes, a drawing activity and worksheet to complete All work is due TODAY . Make sure you put your name on all your papers.

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MONDAY NOVEMBER 7, 2011

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  1. MONDAY NOVEMBER 7, 2011 • HI guys! – please give the substitute your attention and respect. Any names recorded will have ASD Thursday • Today you have bell work, notes, a drawing activity and worksheet to complete • All work is due TODAY. Make sure you put your name on all your papers. • EVERYTHING EXCEPT BELL WORK will be collected • Next slide for BELL WORK

  2. BELL WORK REMEMBER - COPY and ANSWER QUESTIONS • 1. What type of map is used to show elevation?2. What is used to show elevation on this type of map?

  3. BELL WORK ANSWERS • 1. What type of map is used to show elevation? TOPOGRAPHIC MAP2. What is used to show elevation on this type of map? CONTOUR LINES TIME FOR NOTES……… …notes will be collected …………

  4. VOLCANOES

  5. The Nature of Volcanic Eruptions Factors that determine the violence of an eruption 1 - Composition of the magma Viscosityis the measure of a material's resistance to flow. • Factors affecting viscosity a. -Temperature - hotter magmas are less viscous) b. - Composition (silica content) High silica—high viscosity (e.g., rhyolitic lava) 2. Low silica—lowviscosity (e.g., basaltic lava)

  6. The Nature of Volcanic Eruptions Factors that determine the violence of an eruption 2- Dissolved gases a. Violence of an eruption is related to how easily gases escape from magma b. - Gases escape easily from fluid magma. c. - Viscous magma produces a more violent eruption.

  7. Magma Composition

  8. The Nature of Volcanic Eruptions VOLCANIC MATERIALS 1- Lava Flows • Basaltic lavas are more fluid. Types of lava - Pahoehoe lava (resembles braids in ropes) - Aa lava (rough, jagged blocks)

  9. 2 - Gases • One to 5 percent of magma by weight Mainly water vapor and carbon dioxide

  10. The Nature of Volcanic Eruptions VOLCANIC MATERIALS 3 - Pyroclastic Materials - particles produced in volcanic eruptions Types of pyroclastic material - Ash and dust—fine, glassy fragments - Pumice—frothy, air-filled lava - Lapilli—walnut-sized particles - Cinders—pea-sized particles - Blocks—hardened lava - Bombs—ejected as hot lava

  11. Pyroclastic Flow Travels up to 150 mph and is up to 500 degrees hot

  12. 10.1 The Nature of Volcanic Eruptions Anatomy of a Volcano • 1. A volcano is a mountain formed of lava and/or pyroclastic material. • 2. crater - depression at the summit of a volcano. • 3. Aconduit, or pipe, carries gas-rich magma to the surface. • 4. VENTis an opening in the surface of Earth through which molten rock and gases are released.

  13. Composite Cone

  14. The Nature of Volcanic Eruptions TYPES of VOLCANOES 1 - Shield Volcanoes • are broad, gently sloping volcanoes built from fluid basaltic lavas.

  15. Iceland Shield Volcano

  16. 2 - Cinder Cones Cinder Cone • are small volcanoes built primarily of pyroclastic material ejected from a single vent. - Steep slope angle - Frequently occur in groups - Rather small in size

  17. The Nature of Volcanic Eruptions TYPES of VOLCANOES - Most are adjacent to the Pacific Ocean (e.g., Mt. Rainier). 3 - Composite Cones • composed of both lava flows and pyroclastic material. Large size Interbedded lavas and pyroclastics Most violent type

  18. Composite Cone

  19. Mount St. Helens Before and After the May 18, 1980, Eruption

  20. The Nature of Volcanic Eruptions Other Volcanic Features Calderas - large depressions in volcanoes • Nearly circular • Formed by collapse • Size exceeds one kilometer in diameter Lava Plateaus - Fluid basaltic lava extruded from crustal fractures called fissures.

  21. Intrusive Igneous Activity 1. Plutons- intrusive igneous structures that result from the cooling and hardening of magma beneath the surface of Earth.

  22. Sill Intrusive Igneous Activity • Sills and Laccoliths - are plutons that form when magma is intruded close to the surface 3. Laccolithsare lens-shaped masses that arch overlying strata upward. 2. Sillsresemble buried lava flows and may exhibit columnar joints.

  23. Intrusive Igneous Activity • Many dikesform when magma from a large magma chamber invades fractures in the surrounding rocks. 4. Dikesaretabular-shaped intrusive igneous features that cut across preexisting rock layers.

  24. Intrusive Igneous Activity 5. Batholithsarelarge masses of igneous rock that formed when magma intruded at depth, became crystallized, and subsequently was exposed by erosion.

  25. Types of Igneous Plutons

  26. Basaltic Magma at the Surface

  27. Plate Tectonics and Igneous Activity The basic connection between plate tectonics and volcanism is that plate motions provide the mechanisms by which mantle rocks melt to generate magma. CONVERGENT PLATE BOUNDARIES Ocean-Continent Ocean-Ocean •Rising magma can form continental volcanic arcs (Andes Mountains). Rising magma can form volcanic island arcsin an ocean (Aleutian Islands).

  28. Continent - Continent PLUTONS

  29. Convergent Boundary Volcano

  30. Plate Tectonics and Igneous Activity DIVERGENT PLATE BOUNDARIES The greatest volume of volcanic rock is produced along the oceanic ridge system. • Lithosphere pulls apart. • Less pressure on underlying rocks • Partial melting occurs • Large quantities of fluid basaltic magma are produced.

  31. Plate Tectonics and Igneous Activity • Intraplateigneous activity that occurs within a tectonic plate away from plate boundaries • Most intra-platevolcanism occurs where a mass of hotter than normal mantle material called amantle plumerises toward the surface • The activity forms localized volcanic regions called hot spots • Examples include the Hawaiian Islands and the Columbia Plateau.

  32. OK – end of notes. Please pass in your papers to the middle of the room for collection NEXT – follow instructions on the VOLCANO ANATOMY activity. Use the photo of Mt St. Helens as your model for a composite(strato) volcano Make sure you return the colored pencils when you are finished. Have a great day!

  33. Intrusive Igneous Activity • Geologists conclude that magma originates when essentially solid rock, located in the crust and upper mantle, partially melts. • The most obvious way to generate magma from solid rock is to raise the temperature above the level at which the rock begins to melt. Role of Heat Role of Water • The geothermal gradient—Earth’s natural temperature increases with depth but is not sufficient to melt rock in the lower crust and upper mantle Additional heat is generated by - friction in subduction zones - crustal rocks heated during subduction - rising, hot mantle rocks • Causes rock to melt at a lower temperature • Plays an important role in subducting ocean plates

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