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Igneous Rocks

Igneous Rocks. Definition, Classification, Formations. Igneous Rocks: Outline. Rocks in General Intro. to the Rock Cycle Definition of an Igneous Rock How igneous rocks “fit in” the Cycle Classification of an Igneous Rock Crystal Size and Implications Composition and Implications

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Igneous Rocks

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  1. Igneous Rocks Definition, Classification, Formations

  2. Igneous Rocks:Outline • Rocks in General • Intro. to the Rock Cycle • Definition of an Igneous Rock • How igneous rocks “fit in” the Cycle • Classification of an Igneous Rock • Crystal Size and Implications • Composition and Implications • Igneous Rock Formations • Intrusions • Other

  3. What is rock? • Rock = collection of minerals • i.e., several natural, pure compounds in a solid mixture • Type of rock depends on process of formation http://en.wikipedia.org/wiki/File:Rhcp-live-pinkpop05.jpg

  4. Intro. to the Rock Cycle http://www.washington.edu/uwired/outreach/teched/projects/web/rockteam/WebSite/rcycle.gif

  5. Igneous Rocks:Definition • Igneous rocks are solidified from hot liquid materials • i.e., cooled from magma OR lava http://en.wikipedia.org/wiki/File:Pahoeoe_fountain_edit2.jpg

  6. Igneous Rocks:Classification • Classified by two criteria • “Texture”: size of the crystals • three distinctions (see upcoming slides) • Composition: the minerals present in the rock • especially how much SILICA (i.e., SiO2) • multiple distinctions (see upcoming slides)

  7. Texture Vocabulary • Crystal Size involves three main distinctions Coarse Grained Fine Grained No Crystals http://upload.wikimedia.org/wikipedia/commons/thumb/b/bc/Fj%C3%A6regranitt3.JPG/640px-Fj%C3%A6regranitt3.JPG http://en.wikipedia.org/wiki/File:BasaltUSGOV.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Lipari-Obsidienne_%285%29.jpg/640px-Lipari-Obsidienne_%285%29.jpg

  8. Rock Cycle: What Can Texture Tell Us? http://www.washington.edu/uwired/outreach/teched/projects/web/rockteam/WebSite/rcycle.gif

  9. Texture Indicates Cooling Time Intrusive Igneous Rocks Extrusive Igneous Rocks Cooled from lava above the surface from volcanoes, e.g. Can cool in a few days or even minutes Fine grains or no crystals • Cooled from magma under the surface • Can take millions of years • Coarse grains http://en.wikipedia.org/wiki/File:Diorite2.tif http://en.wikipedia.org/wiki/File:Teidepumice.jpg

  10. Porphyry – Mix and Match!What could cause coarse AND fine grains? http://en.wikipedia.org/wiki/File:Rhyolite_porphyry.jpg

  11. Composition Vocabulary • More Silica = Felsic • Less Silica = Mafic • Usu. more iron and magnesium • Other distinctions • Intermediate • Ultramafic! • FELSIC IS LIGHT almost always • MAFIC IS DARK http://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/PinkRhyolite.tif/lossy-page1-640px-PinkRhyolite.tif.jpg http://en.wikipedia.org/wiki/File:BasaltUSGOV.jpg

  12. What Composition Tells Us • More silicates (felsic) are more viscous when liquid • i.e., they resist flow and cause different formations • Less silicates (mafic) are denser • may indicate the source of the magma/lava http://en.wikipedia.org/wiki/File:Pahoeoe_fountain_edit2.jpg http://en.wikipedia.org/wiki/File:Mayon_0052.jpg

  13. Six Common Igneous Rocks(In Words)

  14. Six Common Igneous Rocks(In Pictures) http://en.wikipedia.org/wiki/File:Amygdaloidal_andesite.jpg http://en.wikipedia.org/wiki/File:GabbroRockCreek1.jpg

  15. Igneous Rock Formations:Intrusions • Intrusions form from intrusive rock • Can take millions of years to form, followed by a very long time to surface • Types that we study: • Batholiths • Stocks • Laccoliths • Dikes • Sills

  16. Batholiths and Stocks • Batholith from Greek, “deep rock” • HUGE intrusions • form deep in the Earth’s crust • most are granite • Stocks are just smaller versions (may be tip of a batholith) http://en.wikipedia.org/wiki/File:Enchanted_rock_2006.jpg http://en.wikipedia.org/wiki/File:Half_Dome_from_Glacier_Point,_Yosemite_NP_-_Diliff.jpg

  17. Laccoliths and Dikes • Laccolith from Greek, “pond rock” • magma intrudes into a space, causing layers of rock to bulge into an arch • Dikes are thin intrusions that cut across layers http://en.wikipedia.org/wiki/File:Laccolith.svg

  18. Examples http://en.wikipedia.org/wiki/File:Laccolith_Montana.jpg http://en.wikipedia.org/wiki/File:Dike_diabase_AZ.jpg

  19. Intrusions that get in between layers Resemble laccoliths, but remain flat (no arch) Sills http://en.wikipedia.org/wiki/File:Sill.JPG

  20. Example http://en.wikipedia.org/wiki/File:Edinburgh_Salisbury_Crags_2004-05-18.jpg

  21. Lava Plateaus Layers of lava that have built up Formed as lava flows over flat areas Any volcanoes are also extrusions (details in a later unit) Igneous Rock Formations:Extrusions http://en.wikipedia.org/wiki/File:Pahoeoe_fountain_edit2.jpg

  22. Example

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