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  2. I. What is a rock? Rock - two or more minerals (found in the earth’s crust) bound together in a solid form

  3. II. Rock types A. Sedimentary rocks- formed by the hardening and cementing of layers of sediment.

  4. II. Rock types B. Metamorphic rocks- formed when rocks that already exist are changed by heat and pressure into new kinds of rocks.

  5. II. Rock types C. Igneous rocks- formed by cooling and hardening of hot molten rock from inside the Earth. Hot molten rock from inside the earth is called magma.

  6. III. Igneous Rock Formation A. Magma - molten (liquid) rock found beneath the earth’s surface.Intrusive Rock - rock formed underground when magma cools

  7. III. Igneous Rock Formation A. From Magma (Intrusive ) Cooled slowly Deep Shallow Large/Coarse Small Crystals Crystals

  8. III. Igneous Rock Formation B. Lava - magma on the surface of the earthExtrusive Rock - rock formed on the surface when lava cools

  9. III. Igneous Rock Formation B.From Lava (Extrusive) Cooled quickly Surface Fine Crystals Glassy Rocks

  10. IV. Igneous Rock Characteristics A. Felsic (feldspar and silica--Granitic, Continental) • Chemistry: High percent of silicates (Si) and water. Low percent of iron (Fe), calcuim (Ca), & magnesium (Mg) • Color: Light colored minerals • Viscosity: More viscous (Thick--Low temperatures and slow flowing) • Trapped gases: H2O, O, CO2, H2, CO, H2S, SO2 • Density: Low level (high gas content) • Volcanic source: Explosive volcanoes, and cinder cones

  11. IV. Igneous Rock Characteristics B. Mafic (Magnesium and iron--Basaltic, Oceanic) • Chemistry: Low percent of silicates (Si). High in Ca, Fe, Mg. • Color:Dark colored minerals • Viscosity:Low viscosity (thin--high temperature and more fluid) • Trapped gases: fewer present • Density: Higher level (few gases) • Volcanic source: “Gentle” eruption volcanoes , form broad shieldvolcanoes likeHawaii, ocean ridges

  12. IV. Igneous Rock Characteristics C. Andesitic (Intermediate, Continental) • Chemistry: Intermediate percent of silicates (Si). Intermediate in Ca, Fe, Mg. • Color: Intermediate colored minerals • Viscosity: Intermediate viscosity (fluidity) • Trapped gases: Intermediate amounts present • Density: Intermediate level • Volcanic source: Intermediate eruption volcanoes

  13. IV. Igneous Rock Characteristics (D. Review) A. Felsic B. Mafic Mostly light Mostly dark colored minerals colored minerals [ Si] [Ca, Fe, Mg] [ Si] [Ca, Fe, Mg] C. Andesitic Contain light and dark minerals Intermediate levels of [Si, Ca, Fe, Mg]

  14. IV. Igneous Rock Characteristics (D. Review) A. Felsic Dissolved B. Mafic DissolvedGases Gases Thick & Slow Thin & Fast Hard For Gases Gases Escape To Escape Easily Explosive Eruptions “Gentle” Eruptions Note: Dissolved Gases Include H2O, S, CO2, H2, CO, H2S, SO2

  15. IV. Igneous Rock Characteristics D. Review

  16. IV. Igneous Rock Characteristics (D. Review) Darker colored rocks Lighter colored rocks Large crystals Intrusive Small crystals Extrusive NO crystals

  17. V. Plate Tectonics and Igneous Rocks

  18. VI. How we study rocks A. Color: Lightness/darkness indicates chemistry. Darker rocks tend to have more iron (Mafic),lighter rocks have more silicon (Felsic). B. Crystal size: Can be measured in millimeters using a hand lens/microscope and ruler. Larger crystals need more time to form and are found in rocks that cool slowly (intrusive).

  19. Felsic Fine crystals Mafic Andesitic Small crystals Large crystals

  20. VI. How we study rocks C. Density: mass (g) ÷ volume (ml or cm3). More dense rocks formed from magma that originates deeper in mantle (less explosive volcanoes) and contain fewer gases (Mafic). Less dense rocks formed from magma that originates from outer mantle (more explosive volcanoes) and contain more trapped gases due to interaction with ocean water (Felsic).

  21. THE END