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Chapter Three

The Rock Cycle. A rock is a naturally formed, consolidated material usually composed of grains of one or more mineralsThe rock cycle shows how one type of rocky material gets transformed into anotherRepresentation of how rocks are formed, broken down, and processed in the geosphereArrows indicate

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Chapter Three

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    1. Chapter Three Igneous Activity and Plate Tectonics

    3. CHAPTER – 3 IGNEOUS ROCKS *IGNEOUS ROCKS: ROCKS THAT COOLED AND FIRE CRYSTALLIZED DIRECTLY FROM MOLTEN ROCK, EITHER AT THE SURFACE OR DEEP UNDERGROUND *MAGMA: MOLTEN ROCK WITHIN THE EARTH *LAVA: WHEN MAGMA REACHES EARTH’S SURFACE *MOST IGNEOUS PROCESSES ARE HIDDEN FROM VIEW *REGIONAL EROSION EXPOSES ANCIENT IGNEOUS EVENTS

    4. DISTRIBUTION OF MAJOR CONTINENTAL IGENOUS ROCKS

    5. MOLTING ROCKS AND CRYSTALLIZING MAGMA MAGMA FORMATION: HEATED UNGERGROUND MINERALS – BONDS BROKEN- BECOMES MAGMA – CHEMICAL COMPOSITION OF MAGMA CHANGES MAGMA COOLING AND CRYSTALLIZATION: AS COOLING PROGRESSES, DIFFERENT MINERALS CRYSTALLIZE  

    6. EFFECT ON THERMAL ENERGY

    8. CLASSIFICATION OF IGNEOUS ROCKS: TEXTURE: SIZE AND SHAPE OF MINERAL CRYSTALS CRYSTAL GROWTH DURING COOLING MINERAL CONTENT:CHEMICAL COMPOSITION COOLING HISTORY TEXTURE: RATE AT WHICH MAGMA OR LAVA COOL WHEN 100 – 1000 YRS FOR COOLING TIME TO GROW LARGER CRYSTALS ? CRYSTALS CAN BE VISIBLY SEEN ? PHANERTIC TEXTURE   INTRUSIVE ROCKS (OR PLUTONIC ROCKS) SLOW COOLING OCCURS WHEN MAGMAS INTRUDE PREEXISTING SOLID ROCKS

    11. *VOLCANIC GLASS: WHEN LAVA SUDDENLY COOLS, NO TIME TO FORM CRYSTALS. TEXTURE IS GLASSY. *PUMICE: FORMS WHEN HIGHLY GASEOUS, SILICA – RICH LAVA COOLS VERY RAPIDLY *OBSIDIAN: VERY Si-RICH LAVAS CONTAINING LESS GAS, COOL VERY QUICKLY  

    14. IGNEOUS COMPOSITION   MAGMA ? O2, Si, Al, Fe, Ca, Mg, Na, K, S. DISSOLVED GASSES ? WATER VAPOR, CO2, SO2. SILICATES ARE THE MAJOR CONSTITUENTS OF IGNEOUS ROCKS

    16. CLASSIFICATION OF IGNEOUS ROCKS AND MAGMAS

    17. IGNEOUS ROCK - CHART

    19. CREATION OF MAGMA: * PARTIAL MELTING   ? WHEN ROCKS MELT TO PRODUCE MAGMA ? PARTIAL MELTING ? DIFF. MELTING POINT EX: ALBITE = 1118 0C ANORTHITE = 1553 0C   * MELTING OF ROCKS DEPENDS ON   ? HEAT ? PRESSURE ? AMOUNT OF H2O IN THE ROCKS.   THERMAL ENERGY

    20. HEAT SOURCES

    21. GEOTHERMAL GRADIENT

    22. MELTING TEMPERT.-DRY

    23. MELTING TEMPERT.-WET

    24. FLUIDITY AND VISCOSITY OF MAGMA:   MAGMA RISES BECAUSE   ? IF IT IS LESS DENSE THAN SURROUNDING ROCK ? EXPANDING GASES DRIVE IT UPWARD ? IT IS SQUEEZED UPWARD BY SURROUNDING ROCKS   VISCOSITY: FLUID RESISTANCE TO FLOW      A) INCREASES WITH DECREASING TEMPERATURE       B) MINERAL (SILICA) CONTENT INCREASES VISCOSITY VALUE.

    25. CRYSTALLIZATION OF MAGMA: *MINERALS MELT AT THE SAME TEMPERATURE AT WHICH THEY CRYSTALLIZE ? FIRST TO MELT ? LAST TO CRYSTALLIZE * AT EACH STAGE OF COOLING,   CRYSTAL/LIQUID RATIO CHANGES  

    26. OCEANIC PLATE SUBDUCTS

    27. MAGMA MIXING

    28. BOWEN’S REACTION SERIES: A)     BOTH MAFIC AND FELSIC ROCKS CAN CRYSTALLIZE FROM AN ORIGINALLY MAFIC MAGMA B)      EARLY – FORMING CRYSTALS REMAINING IN CONTACT WITH THE STILL – LIQUID MAGMA REACT WITH IT TO EVOLVE INTO DIFFERENT MINERALS

    29. BOWEN’S REACTION SERIES

    31. EARLY-FORMING CRYSTALS

    32. MAGMA & EARLY FORMING CRYSTALS

    33. SILICATE MINERALS CAN CRYSTALLIZE FROM MAFIC MAGMAS TWO WAYS: DISCONTINUOUS SERIES   OLIVINE PYROXINE AMPHIBOLE BIOTITE MICA MINERALS WITHOUT Fe, Mg.     CONTINUOUS SERIES CALCIUM PLAGIOCLASE SODIUM PLAGIOCLASE

    34. CONTD-

    35. HOW MAGMA CHANGES AS IT COOLS:

    36. INTRUSIVE ROCK FORMATION: RISING MAGMA MAY FORCE OVERLYING ROCKS TO BULGE UPWARD ? RESULTING ROCK APPEARS AS A DOOMED INTRUSION WITHIN OTHER ROCKS ? THIS STRUCTURE IS KNOWN AS DIAPIR   XENOLITHS: WHEN PREEXISTING ROCK IS ASSIMILATED IN A MAGMA, THEY APPEAR IN THE SOLIDIFIED ROCK AS DISTINCT BODIES – XENOLITHS

    37. PLUTONS: MAGMA THAT COOL UNDERGROUND FORM PLUTONS

    38. TABULAR PLUTONS DIKES SILLS – DISTINGUISHED FROM EXTRUSIVE FLOWS BY   A)EVIDENCE OF HEATING OF ADJACENT ROCK SURFACES B)EVIDENCE OF INCLUSIONS OF COUNTRY ROCK IN BOTH UPPER & LOWER SILL SURFACE C)LACK OF VESICLES ( HOLES FROM GAS BUBBLES ) ON UPPER SURFACE D)LACK OF WEATHERING OF LARGE SURFACE.

    39. PLUTONIC IGNEOUS FEATURES

    40. BATHOLITHS AND LARGE PLUTONS: 1.        LACCOLITHS 2.        LAPOLITHS     3.        BATHOLITHS   A)DEFINITION B)EXAMPLES C)TEXTURE  

    41. SEMINARY RIDGE TOPOGRAPHIC RIDGE

    42. SILLS AND LAVA FLOWS

    43. LACCOLITH

    44. PLATE TECTONICS AND IGNEOUS ROCKS: A) THE ORIGIN OF BASALT & GABBROS   1) INTRODUCTION   * UPPER MANTLE LACKS LIGHT ELEMENTS *DEEPER MANTLE POSSESSES SOME LIGHT ELEMENTS *PRESENCE OR ABSENCE OF LIGHT ELEMENTS IN GABBRO & BASALT IDENTIFIES SOURCE OF PARENT MAGMA

    47. PLATE SETTINGS & BASALTS

    48. BASALTS-OCEAN & LAND

    49. ANDESITE & DIORITE ORIGIN

    50. B) ORIGIN OF ANDESITES & DIORITE

    51. GEOLOGY AT A GLANCE

    52. CHAPTER SUMMARY

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