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Igneous Rocks

Igneous Rocks. Mt. Rushmore. Half Dome, Yosemite, CA Ansel Adams. IGNEOUS ROCKS Some igneous rocks form from cooled lava that has exited Earth’s crust. Hawaii. Some Igneous rocks cool from magma inside Earth and later become exposed through pressure, uplift, and erosion!!!.

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Igneous Rocks

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  1. Igneous Rocks Mt. Rushmore

  2. Half Dome, Yosemite, CA Ansel Adams

  3. IGNEOUS ROCKS Some igneous rocks form from cooled lava that has exited Earth’s crust Hawaii

  4. Some Igneous rocks cool from magma inside Earth and later become exposed through pressure, uplift, and erosion!!! Half Dome, Yosemite, California

  5. Igneous • Think of “ignite” • To light a fire • Igneous rock comes from the heat withinEarth: Geothermal

  6. How are Igneous Rocks Classified? Igneous rocks are classified by: • 1. Mineral Composition • 2. Crystal Size (Texture)

  7. Igneous Rock Formation Most Igneous rocks form directly from Magmawhich is hot, molten rock • Granite is the most common igneous rock, it cooled from magma Igneous rocks can also form from lava

  8. 3. First Classification of Magma: Felsic • Is rich in Silica (SiO2) • Small amounts of Ca, Fe, Mg (Calcium, Iron, & Magnesium) • Slow-moving, thick= HIGH VISCOSITY (resistance to flowing) • Crystallizes to light-coloredminerals • Resulting rocks have relatively low density • Felsic rocks make up the continents

  9. Examples of FELSIC igneous rocks Pumice Rhyolite

  10. 4. Second Classification of Magma: Mafic • Low amounts of Silica (SiO2) • Fe and Mg rich (Iron and Magnesium) • Fast-moving, thinner= LOW Viscosity: less resistance to flowing, more fluid • Crystallize to dark-colored minerals • Resulting rocks have relatively high density • Mafic rocks make up the ocean floors

  11. Mafic Igneous Rock examples: Basalt(ocean floor) Gabbro

  12. 5. Crystal Size • It takes time to grow crystals • As magma cools, it crystallizes • If magma cools slowly, what size crystals will form? Large Crystals If Magma cools quickly, small crystals will form because they have little time to grow.

  13. Igneous Rock Obsidian cools so fast that no crystals have time to form A.K.A. Volcanic glass Obsidian is dark in color due to iron oxides.

  14. 6. Igneous Rocks Granite Intrusive • Igneous rock that crystallizes belowEarth’s surface, from magma • Intrusive= Inside Earth Large Crystal size Notice how Granite has large crystals, it cooled slowly from magma deep beneath Earth’s surface

  15. Basalt Igneous Rocks Extrusive • Igneous rock that crystallizes or forms at Earth’s surface, from lava • Extrusive= exited Earth Small Crystal size Notice how basalt has small crystals, it cooled quickly at Earth’s surface

  16. Lava is magmathat has reached the Earth’s surface.

  17. Igneous Rocks EXT-rusive • EXITED Earth IN-trusive • Formed IN-side Earth

  18. Crystal Size Intrusive Rock (Large Crystal Size) • Because it is inside the Earth, it cools very slowly, giving crystals time to grow Extrusive Rock (Small crystal size) • Cools very quickly so crystals do not have time to form

  19. Composition (what it’s made of) of Granite Granite Rock contains the following minerals: • Quartz • Feldspar • Mica

  20. Igneous Rock

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  26. IGNEOUS • FELSIC • Light colored • Less dense • Rich in silica (SiO2) • Magma flows slowly, thick • Continental crust

  27. IGNEOUS • MAFIC • Dark colored • Very dense • Rich in iron (Fe) and magnesium (Mg) • Magma flows quickly, thin • Oceanic crust

  28. IGNEOUS • EXTRUSIVE • “exit” • Magma exits the Earth before cooling • Cools and crystalizes quickly • Small or no crystals

  29. IGNEOUS • INTRUSIVE • “in” • Magma cools inside the Earth • Cools and crystalizes slowly • Large crystals

  30. Igneous Rock Lab • Use your Igneous observations sheet • Rotate independently between the 25 stations set up around the room • Start with whichever station number you are located • Round 1: You will have less than 1 minute at each station • Do not switch to the next station until told to do so, only 1 person at at station (if you have extra time, study your notes) • Round 2: You may go back to any unoccupied station, if needed

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