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Chapter 3

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Chapter 3

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  1. Chapter 3

    ROCKS NJCCCS: 5.4 C – Properties of Earth Materials
  2. What is a Rock? It is a mixture of minerals, mineraloids, glass, or organic matter ex. Granite = mica + quartz + feldspar + hornblende + other minerals
  3. The Rock Cycle
  4. Rock Type Basics Igneous Rocks – form from cooling magma or lava Metamorphic Rocks – form from extreme heat and pressure Sedimentary Rocks – form from the compaction and cementation of sediment (rock fragments)
  5. Weathering (breaking rocks into smaller pieces) Mechanical Weathering – does change chemical composition Chemical Weathering – changes the chemical composition
  6. Erosion Main Agents of erosion 1. Wind 2. Water 3. Glaciers 4. Gravity 5. Animals
  7. Heat and Pressure Heat – radioactive decay, extreme pressure Pressure – thousands of miles of rock pulled together by gravity
  8. Melting Caused by heat due to radioactive decay and pressure
  9. Igneous Rocks Igneous Rocks - cooled molten material form the inside the Earth(magma) or out of a volcano (lava) - the most common rock on Earth
  10. Igneous Rocks B. The Earth’s crust generates great temps (1400), pressures, and radioactive thermal energy C. Rocks and Minerals melt to form magma, minerals have different densities and melting pts
  11. Igneous Rocks D. Magma is less dense than the crust above and forces an escape through volcanoes as lava E. Sometimes magma forces upwards but cools before reaching the surface
  12. Classification of Igneous Rocks (1) Intrusive Igneous Rocks - those rocks that were formed from cooling magma below the Earth’s surface Cool very slowly Have large crystals called mineral grains Extrusive Igneous Rocks - Rocks that formed from cooling lava on the surface of the Earth -Cool very quickly - Have very fine grained texture
  13. IGNEOUS ROCKS – cooled magma or lava Intrusive igneous rocks have large mineral grains!!!!! Extrusive igneous rocks have virtually no mineral grains.
  14. Classification of Igneous Rocks (2) 1. Basaltic – dense, heavy, dark colored rock, rich in magnesium and iron, most common 2. Granitic – light color, less dense, rich in silicon and oxygen 3. Andesitic – mineral compositions in between the two, common among Pacific Volcanoes
  16. Igneous Features

  17. Intrusive Igneous Features Magma Chamber is a large underground pool of molten rock found beneath the surface of the Earth.
  18. Intrusive Igneous Features Sill is an intrusion of magma that solidifies into a horizontal layer of igneous rock
  19. Intrusive Igneous Features Dike is a magma that cuts across rock layers (vertical)
  20. Intrusive Igneous Features Batholith is a magma chamber that cools before reaching the surface to form a volcano
  21. Intrusive Igneous Features Laccolith is a small magma chamber at shallow depth (roughly lens shaped)
  22. Extrusive Igneous Features Volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface 3 types: Shield Composite Cinder
  23. Extrusive Igneous Features Lava Flow – different types of lava depending on the composition and temperature
  24. Extrusive Igneous Features Ash and Dust Particles
  25. Extrusive Igneous Features Pyroclastic Flow is a fast-moving current of extremely hot gas ( 1,830 °F) and rock which travel away from a volcano at speeds generally as great as 450 mph.
  26. Sedimentary Rocks

  27. Sedimentary Rocks 3 Types of Sedimentary Rocks 1) Clastic – made from rock fragments 2) Chemical – evaporation or precipitation from solution 3) Organic – contains fossils
  28. Classification of Sedimentary Rocks 1) Clastic Made from sediments
  29. Chemical – evaporation/precipitation
  30. Organic – contain fossils Coquina Fossil-rich limestone
  31. Formation of Sedimentary Rocks Weathering and erosion makes sediment!!!! Glaciers Wind Gravity Water
  32. Sediment Sorting Clastic Sedimentary Rocks are made of rock fragments. Parent Rock – source of rock fragments
  33. Sediment Sorting -As erosional forces lose energy, sediment is deposited largest first-smallest last
  34. Sediment Sorting Largest to Smallest Boulder Cobble Gravel Pebble Sand Silt Clay
  35. Conglomerate Pebbles ------------------- Conglomerate
  36. Sandstone Sand -------------------- Sandstone
  37. Siltstone Silt --------------------- Siltstone
  38. Shale Clay ---------------------- Shale
  39. Sediment Sorting
  40. Organic Sedimentary Rock Coal – formed from the Remains of plants at the Bottom of a body of water Limestone – formed from the mixed skeletal remains of marine organisms
  41. Chemical Sedimentary Rock Gypsum – easily dissolves in water… gypsum rock forms when the water evaporates and crystallizes Halite – (salt) – easily dissolves in water…halite forms when the water evaporates and crystallizes
  42. Metamorphic Rocks
  43. Metamorphic Rocks Metamorphic Rocks - rocks that have changed due to increases in temperature and pressure - igneous, sedimentary, metamorphic rocks can metamorph B. Ex. Basalt  Schist  Gneiss Shale  Slate Phyllite Gneiss Granite  Gneiss
  44. Metamorphic Rocks Occurs in 2 general ways: 1) Contact Metamorphism 2) Regional Metamorphism
  45. Contact Metamorphism As magma pushes through rock layers beneath the Earth…nearby rock change slightly in composition and structure
  46. Regional Metamorphism As the Earth’s plates move, the same extreme pressures that build mountains also cause rocks to deform and change in composition
  47. WHAT HAPPENS? Heat - (2 sources- magma and depth) Minerals within the rock melt and re-crystalize thus changing the composition of the rock
  48. WHAT HAPPENS? Pressure – causes space between minerals to close – compacted often causing minerals to recrystalize
  49. 2 classifications Foliated – banded (layers) of minerals at 90 degree angles to the pressure that caused the metamorphism Non-Foliated – no bands or layers (usually composed of only one type of mineral)
  50. Metamorphic Rocks – HEAT AND PRESSURE FOLIATED = bands of mineral grains NON-FOLIATED = no bands of mineral grains
  51. Rock Classification Igneous Metamorphic Sedimentary Intrusive Foliated Clastic Extrusive Non-Foliated Chemical Organic Basaltic Andesitic Granitic

    NJCCCS: 5.4B History of the Earth 5.4.12.B.1, 2, 3
  53. Fossils Fossil - any naturally preserved evidence of past life
  54. Understanding Decomposition When an organism dies specialist organisms called decomposers and detritivores begin consuming its remains. Decomposers are usually bacteria and fungi (think sour milk and moldy bread) Detritivores are animals like vultures, hyenas, insect larvae, and a host of others (think maggots in a garbage can) Most often only the hard tissue of the organism is left behind… bones and teeth, shells, exoskeletons, etc. See Video clip – Blue Planet
  55. Fossils Are Rare Fossils only form under very special environmental conditions!!!!!!! Usually found in sedimentary rocks…why? Exceptions: Volcanic ash
  56. 3 ways in which fossils form 1) Mineral Replacement 2) Mostly Unchanged 3) Trace
  57. Mineral Replacement Underground water removes original material 1 atom at a time and replaces it with minerals. An exact copy is created out of the minerals calcite, pyrite, or silica. *Most Common way in which fossils form 3 basic types Petrification, Molds, Casts
  58. 1) Petrification the organism gets totally replaced with minerals
  59. 2) Molds dead creature is covered with sediments and decays away. The remaining cavity in the shape of the original creature is the fossil = impression
  60. 3) Cast Minerals from ground water seep into the mold, precipitate out of solution, and a stone shape is the fossil
  61. Mostly Unchanged Actual original parts of an organism are left behind by several methods. 1) Simple Burial 2) Frozen 3) Amber 4) Mummification 5) Acidic Peat Bogs 6) Tar SPECIAL ENVIRONMENTAL CONDITIONS EXIST THAT PREVENT DECOMPOSITION!!!!
  62. 1) Simple Burial bones and teeth most often remain…share similar properties to minerals (calcium carbonate)
  63. 2) Frozen soft parts of mammoths have been found in frozen arctic tundra Why do we put food in a freezer? Slows down decomposition!!
  64. 3) Amber resin or ancient tree sap captured creatures (insects, frogs, etc.)
  65. 4) Mummification creatures desiccate (dry out) and soft parts remain – salt and or lye prevent decomposition
  66. 5) Acidic Peat Bogs creatures have been preserved in some wetlands that have environmental conditions that prevent decomposition (lack of oxygen, extreme pH)
  67. 6) Tar ancient oil seeping from underground trapped creatures. La Brea Tar Pits in California hold bones of mammoths, sabertooth tigers, camels, and more. Tar prevented decomposition.
  68. Trace Fossil Evidence Evidence of past life not including plant or animal remains
  69. 1) Footprints 2) Burrows 3) Borings (holes) 4) Coprolites (fossil dung)
  70. Fossil Lab - BE CAREFUL Some things look like fossils but really aren’t…called rock features. Ripple Marks Geodes Cross Bedding
  71. Common fossils in your lab Coprolites Belemite (dung) (Squid) Trilobite Stromatolite(colony of bacteria) (arthropod) Ammonite (cuddlefish)