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Bowen’s Reaction Series

Hot. Melting. Crystallization. Cold. Bowen’s Reaction Series . Different minerals crystallize from magmas at different temperatures. Daily Question .

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Bowen’s Reaction Series

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  1. Hot Melting Crystallization Cold Bowen’s Reaction Series • Different minerals crystallize from magmas at different temperatures

  2. Daily Question • The core (center) of the Black Hills of South Dakota is composed of granite. The Columbia River Plateau of Washington and Oregon is composed of basalt. Using a Venn Diagram, compare and contrast the two locations highlighting the composition of the rocks, the texture of the rock, and the location (depth) where the rocks formed.

  3. Magmatic Differentiation • Formation of more than one magma from a single parent magma

  4. Magmatic Differentiation • Crystal Settling: crystallized minerals have a density greater than the magma and settle to the bottom due to gravity • Because Fe and Mg are first removed, melt becomes rich in SiO2, Na, and K • Marbles analogy

  5. Magmatic Differentiation • Assimilation: magma reacts with the “country rock” which is adjacent to the magma chamber • Magma composition is altered according to the composition of the assimilated country rock • Inclusions are rocksIncompletely melted chunks of country rock

  6. Magmatic Differentiation • Magma Mixing: Magmas of different compositions are mixed together • Resulting magma is of a composition intermediate between the parents

  7. Magma Mixing

  8. Magma Mixing

  9. Magma Mixing

  10. Fig. 7.21

  11. Igneous Activity

  12. Fig. 6.4 Viscosity Controls Violent Nature of Volcanic Eruptions

  13. Controls of Viscosity • Magma composition – silica content • High silica content – high viscosity • Low silica content – low viscosity • Temperature • High temperature – low viscosity • Low temperature – high viscosity • Dissolved gas • Low viscosity – gases escape • High viscosity – gases cannot escape (pressure builds up)

  14. Magma Properites

  15. Materials Extruded During an Eruption • Lava flows – low silica content of basalt lava allows it to flow up to 30 km/hour, typically 10 to 300 m/hour • Gases – reduction of confining pressure allows gases to escape • 70% water vapor • 15% carbon dioxide • 5% nitrogen • 5% sulfur dioxide • Trace amounts of chlorine, hydrogen, and argon • Pyroclastic material – welded ash, dust, and lava

  16. Nuée ardente • Glowing avalanche of ash, steam, gas, and pyroclastics • Travels at speeds of 200 km/ hr (125 mph)

  17. Page 160

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