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Igneous rocks

Igneous rocks. Crystallize from a molten rock: magma Magma: liquid rock beneath earth’s surface Lava: liquid rock above earth’s surface Igneous rocks classified on Mineral size composition. Igneous rocks. Intrusive igneous rocks Cool below ground (slowly)

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Igneous rocks

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  1. Igneous rocks • Crystallize from a molten rock: magma • Magma: liquid rock beneath earth’s surface • Lava: liquid rock above earth’s surface • Igneous rocks classified on • Mineral size • composition

  2. Igneous rocks • Intrusive igneous rocks • Cool below ground (slowly) • All minerals visible w/out microscope • Extrusive igneous rocks • Cool above ground (fast) • Most minerals too small to see w/out microscope

  3. Igneous rocks • Intrusive igneous rocks • Extrusive igneous rocks

  4. Intrusive or extrusive?

  5. Slow or fast cooling?

  6. Intrusive or extrusive?

  7. Slow or fast cooling?

  8. Light colored igneous rocks • Granite and rhyolite

  9. Intermediate igneous rocks • Andesite

  10. Dark colored igneous rocks • Gabbro and basalt

  11. Aphanitic Texture – Rapid Cooling Small Crystals

  12. Phaneritic Texture – Slow Cooling Large Crystals

  13. Glassy Texture - Very Rapid Cooling - No Crystal Structure

  14. Where do igneous rocks form?

  15. What is left behind when igneous rocks cool?

  16. Rock Cycle • Igneous rocks can become what other kind of rocks?

  17. Metamorphic rocks • Formed by transformation of other rocks • Heat and pressure do this transforming! • End up with • New minerals • And/or texture changes

  18. Metamorphic textures • Foliated: alignment of minerals • Rock looks banded/layered • Nonfoliated: random orientation of minerals

  19. Foliated or nonfoliated?

  20. Foliated metamorphic rocks • Smallest minerals • Slate • Clue: like shale/mudstone but harder

  21. Foliated metamorphic rocks • Schist • Shiny with bigger minerals

  22. Foliated metamorphic rocks • Gneiss • Big minerals • Looks like a granite with bands of color

  23. Nonfoliated met. rocks • Marble • Made of calcite • Best way to ID?

  24. Nonfoliated met. rocks • Quartzite • Can look like marble, but no fizz with acid

  25. Nonfoliated met. rocks • Greenstone • Clue: green basalt

  26. Rock Cycle

  27. Sedimentary rocks • Clastic sed rock: made of solid particles once part of other rocks • Classified by grain size • Chemical sed rock: made from dissolved material in water • Classified by chemical composition • Biochemical sed rock: made of dead plants and animals

  28. Biochemical, chemical, or detrital?

  29. Clastic sed rocks • Big particles Conglomerate • Sand size Sandstone • Small particles Mudstone (shale)

  30. Clastic sed rocks • Conglomerate • Clue: Particles of lots of different sizes

  31. Clastic sed rocks • Sandstone • Clue: feels sandy

  32. Clastic sed rocks • Mudstone (shale) • Clue: • very small particles • No grit when you taste it

  33. Chemical sed rocks • Limestone • Made of calcite • Clues: • fizzes with acid • Often contains fossils

  34. Chemical sed rocks • Rock salt/halite • Clue: tastes salty • Gypsum • Clue: easily scratched, not salty

  35. Biochemical sed rocks • Category of chemical sed rocks • Coal • Limestone if with fossils

  36. Importance of sed rocks • Key to interpreting Earth’s history

  37. Homework • Go to website and complete the relative age assignment. • Other website for checking to see if you are on the right track! • Websites are on our class page

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