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., SiO 2 ) 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/thu mb/1/17/Lipari-Obsidienne_%285%29.jpg/640px- Lipari-Obsidienne_%285%29.jpg http://en.wikipedia.org/wiki/File:BasaltUSGOV.jpg http://upload.wikimedia.org/wikipedia/commons/ thumb/b/bc/Fj%C3%A6regranitt3.JPG/640px- Fj%C3%A6regranitt3.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 Cooled from magma under the surface Can take millions of years Coarse grains 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 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) Texture → Composition ↓ Fine-GrainedCoarse-Grained Felsic (High Silica) RhyoliteGranite Intermediate (Mid Silica) AndesiteDiorite Mafic (Low Silica) BasaltGabbro

14. Six Common Igneous Rocks (In Pictures) Texture → Composition ↓ Fine-GrainedCoarse-Grained Felsic (High Silica) Intermediate (Mid Silica) Mafic (Low Silica) 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: 1.Batholiths 2.Stocks 3.Laccoliths 4.Dikes 5.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. Sills Intrusions that get in between layers Resemble laccoliths, but remain flat (no arch) http://en.wikipedia.org/wiki/File:Sill.JPG

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

21. Igneous Rock Formations: Extrusions 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) http://en.wikipedia.org/wiki/File:Pahoeoe_fountain_edit2.jpg

22. Example