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CHAPTER 4

CHAPTER 4. ROCKS: MINERAL MIXTURES. Petrology. The study of rocks Petros – means “rock” “petroleum” – means “rock oil” Neat memory aid – the Biblical name “Peter” means – “the rock ”. SECTION 1. UNDERSTANDING ROCK. Difference between rock and mineral.

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CHAPTER 4

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  1. CHAPTER 4 ROCKS: MINERAL MIXTURES

  2. Petrology • The study of rocks • Petros – means “rock” • “petroleum” – means “rock oil” • Neat memory aid – the Biblical name “Peter” means – “the rock”

  3. SECTION 1 UNDERSTANDING ROCK

  4. Difference between rock and mineral • A rock is a MIXTURE OF ONE OR MORE MINERALS • Basically worthless?

  5. Why are rocks important? • BUILDINGS • ROADS • MONUMENTS • TOOLS

  6. Why are rocks important to the scientist? • Used to explore for resources • Can help explain historical stuff like geologic events and ancient life

  7. THE ROCK CYCLE • PROCESS BY WHICH ONE ROCK CHANGES INTO ANOTHER ROCK • THE WAY A ROCK FORMS DETERMINES WHAT TYPE OF ROCK IT IS

  8. Erosion – transport of sediment • Deposition – sediment is dropped

  9. IGNEOUS • FORMS FROM THE COOLING OF MAGMA

  10. SEDIMENTARY • FORMS WHEN SEDIMENTS ARE COMPACTED & CEMENTED TOGETHER

  11. METAMORPHIC • FORMS WHEN PREEXISTING ROCK CHANGES DUE TO HEAT & PRESSURE

  12. MAGMA • HOT LIQUID FORMED WHEN ROCK MELTS • INSIDE THE EARTH

  13. LAVA • HOT LIQUID THAT FLOWS ON THE SURFACE OF THE EARTH

  14. COMPOSITION • MINERALS A ROCK IS MADE OF

  15. TEXTURE • SIZE, SHAPE, & POSITION OF THE GRAINS • Fine, medium, and coarse

  16. FINE-GRAINED • SMALL GRAINS

  17. MEDIUM-GRAINED • Size between fine and coarse (duh!)

  18. COARSE-GRAINED • LARGE GRAINS SUCH AS PEBBLES

  19. SECTION 2 IGNEOUS ROCK

  20. MAGMA FORMATION • INCREASE IN TEMPERATURE • PRESSURE IS RELEASED • CHANGE IN COMPOSITION

  21. 2 properties used to classify igneous rock • Color – indicated by composition • Light or dark • Texture – indicated by size of the crystals • Glassy – no crystals • Fine – small crystals • Coarse – large crystals

  22. Felsic vs. Mafic composition • FELSIC = QUARTZ • MAFIC =NOQUARTZ

  23. FELSIC • Word actually is short for “Feldspar and Silicate” • Lighter colored • Less dense

  24. MAFIC • Magnesium and iron (ferrous) • Dark colored • More dense than the “granite” family

  25. TEXTURE • AMOUNT OF TIME IT TAKES FOR MAGMA / LAVA TO COOL DETERMINES THE TEXTURE

  26. TEXTURE • FAST > FINE-GRAINED • SLOW > COARSE-GRAINED

  27. Intrusive vs. Extrusive • Intrusive = plutonic = under the surface • Coarse texture • Extrusive = Volcanic =above the surface • Fine texture

  28. LAVA FLOW • RIVER OF LAVA • Comes out of a “fissure”

  29. FISSURES • CRACKS THROUGH WHICH MAGMA FLOWS

  30. LAVA PLATEAU • LARGE AMOUNT OF LAVA OVER A VAST AREA • Ex. Columbia Plateau

  31. Igneous Features • Batholith • Laccolith • Dike • Sill • Neck

  32. Devil’s Postpilea lava flow

  33. Batholith • Largest of all igneous intrusions – a huge underground mass of magma – source of magma for many other smaller intrusions

  34. Laccolith • igneous intrusion that pushes up a dome mountain

  35. Batholith, Laccolith, lava flows

  36. Dike • Igneous intrusion that cuts across rock layers

  37. Dike

  38. Sill • Igneous intrusion thatsqueezes between rock layers

  39. Volcanic Neck • Remains of an extinct volcano – the magma left in the vent when it died • Ex. Pilot Mountain NC Ship Rock NM

  40. Pilot Mountain NC

  41. Ship Rock NM

  42. On the Moon • basalt lava flows – the “Maria” or “seas” on the lunar landscape

  43. Maria (the smooth dark areas)

  44. SECTION 3 SEDIMENTARY ROCK

  45. STRATA • LAYERS WITHIN A SEDIMENTARY ROCK

  46. Stratification • LAYERING OF ROCK • DETERMINED BY KIND, SIZE, & COLOR OF SEDIMENT

  47. How does Clastic sed. Rock form? • The “clasts” are glued together with a cement

  48. Lithification • Means to harden into rock • “Lithos” refers to rock (Monolith in Stonehenge)

  49. How do the clasts form? • WEATHERING OF ROCK by wind, water, ice, gravity, etc. • Rock is broken into pieces

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