1. GLG 101 - Physical Geology Bob Leighty Igneous Rocks

2. These lecture notes are very similar to the ones I use in my traditional classes. You’ll find they are loaded with imagery and streamlined text that highlight the most essential terms and concepts. The notes provide a framework for learning and, by themselves, are not meant to be a comprehensive source of information. To take advantage of the global knowledge base known as the Internet, I have included numerous hyperlinks to external web sites (like the Wikipedia, USGS, NASA, etc.). Follow the links and scan them for relevant info. The information from linked web sites is meant to supplement and reinforce the lecture notes – you won’t be responsible for knowing everything contained in them. As a distance learning student, you need to explore and understand the content more independently than in a traditional class. As always, I will help guide you through this learning adventure. Remember, email Dr. Bob if you have any questions about today’s lecture (rleighty@mail.mc.maricopa.edu).rleighty@mail.mc.maricopa.edu Leave no questions behind! Explore and have fun! These notes and web links are your primary “lecture” content in this class. Additionally, various articles are assigned each week to supplement this “lecture” information. I believe you’ll have enough information to reference without having to purchase a costly textbook.

3. >cool and crystallize at depth as intrusionsintrusions > migrate to the surface and erupt as extrusionsextrusions  Most magma initially rises because of its greater buoyancymagmabuoyancy The Life of Magma Igneous Rocks

4. Crustal melting felsic magmas  Texture (crystal size) - mostly related to the cooling rate (largely controlled by where the magma cools)  Composition (mineralogy) - mostly related to what was melted coarse-grained texture Cool slowly at depth fine-grained texture Cool fast on surface granite rhyolite Composition & Texture Igneous Rocks

5. Naming Igneous Rocks Igneous Rocks click on the chart

6. magma Mafic Ca Fe Mg Si O O O O O O O O  Mafic magmas are rich in Fe, Mg, & Ca, but poor in Si, Na, & K Mafic Igneous Compositions Igneous Rocks

7. basalt gabbro …which compose most mafic igneous rocks  Upon cooling, mafic magmas crystallize mafic minerals… olivine pyroxene Ca-feldspar Mafic Igneous Compositions Igneous Rocks

8.  Abundant in the oceanic crust & mantleoceanic crustmantle peridotitegabbrobasalt Mafic & Ultramafic Igneous Compositions Igneous Rocks

9. peridotitegabbrobasalt  Mafic rocks form by partial melting of ultramafic mantleultramafic Mafic & Ultramafic Igneous Compositions Igneous Rocks

10. magma K K Si Na Si O O O O O O O O  Felsic magmas are poor in Fe, Mg, & Ca, but rich in Si, Na, & K Felsic Felsic Igneous Compositions Igneous Rocks

11. …which compose most felsic igneous rocks rhyolite granite  Upon cooling, felsic magmas crystallize felsic minerals… quartz K-feldspar Na- Feldspar mica Felsic Igneous Compositions Igneous Rocks

12. rhyolitegranitepumice  Abundant in the continental crustcontinental crustFelsic Igneous Compositions Igneous Rocks

13. rhyolitegranitepumice  Form by melting continental crustFelsic Igneous Compositions Igneous Rocks

14. magma K Ca Fe Si Mg Na Si O O O O O O O O  “Combo deal” includes some mafic & felsic elements Intermediate Igneous Compositions Igneous Rocks

15. andesite diorite …which compose intermediate igneous rocks  Upon cooling, intermediate magmas crystallize int. minerals… amphibole Ca/Na Feldspar Intermediate Igneous Compositions Igneous Rocks

16. andesite diorite  Abundant in the continental crustIntermediate Igneous Compositions Igneous Rocks

17. andesite diorite  Form by “wet” melting of the mantle and crustIntermediate Igneous Compositions Igneous Rocks

18.  Big crystals (coarse-grained texture) granite > slow cooling at depth (intrusive) microscope view Igneous Textures Igneous Rocks

19.  Small crystals (fine-grained texture) basalt rhyolite > fast cooling on the surface (extrusive) Igneous Textures Igneous Rocks

20.  No crystals (glassy texture) > ultra-fast to cool (quenching) on the surface (extrusive) obsidian Igneous Textures Igneous Rocks

21.  Big & small crystals (porphyritic texture) porphyritic andesite > two stages of cooling: slower & faster cooling (int & ext) microscope view Igneous Textures Igneous Rocks

22. > gas bubbles escaping the magma (extrusive) Igneous Textures Igneous Rocks  Holes or vesicles (vesicular texture) scoria

23.  Pieces of rock (pyroclastic texture) > explosive eruption (extrusive) Volcanic breccia, lapilli, & tuff increasing explosiveness Igneous Textures Igneous Rocks

24. WWW Links in this Lecture > Magma - http://en.wikipedia.org/wiki/Magmahttp://en.wikipedia.org/wiki/Magma > Buoyancy - http://en.wikipedia.org/wiki/Buoyancyhttp://en.wikipedia.org/wiki/Buoyancy > Intrusions - http://en.wikipedia.org/wiki/Intrusionhttp://en.wikipedia.org/wiki/Intrusion > Extrusions - http://en.wikipedia.org/wiki/Extrusivehttp://en.wikipedia.org/wiki/Extrusive > Mafic - http://en.wikipedia.org/wiki/Mafichttp://en.wikipedia.org/wiki/Mafic > Basalt - http://en.wikipedia.org/wiki/Basalthttp://en.wikipedia.org/wiki/Basalt > Gabbro - http://en.wikipedia.org/wiki/Gabbrohttp://en.wikipedia.org/wiki/Gabbro > Oceanic crust - http://en.wikipedia.org/wiki/Oceanic_crusthttp://en.wikipedia.org/wiki/Oceanic_crust > Mantle - http://en.wikipedia.org/wiki/Mantle_%28geology%29http://en.wikipedia.org/wiki/Mantle_%28geology%29 > Peridotite - http://en.wikipedia.org/wiki/Peridotitehttp://en.wikipedia.org/wiki/Peridotite > Felsic - http://en.wikipedia.org/wiki/Felsichttp://en.wikipedia.org/wiki/Felsic > Rhyolite - http://en.wikipedia.org/wiki/Rhyolitehttp://en.wikipedia.org/wiki/Rhyolite > Granite - http://en.wikipedia.org/wiki/Granitehttp://en.wikipedia.org/wiki/Granite > Continental Crust - http://en.wikipedia.org/wiki/Continental_crusthttp://en.wikipedia.org/wiki/Continental_crust > Pumice - http://en.wikipedia.org/wiki/Pumicehttp://en.wikipedia.org/wiki/Pumice > Andesite - http://en.wikipedia.org/wiki/Andesitehttp://en.wikipedia.org/wiki/Andesite > Diorite - http://en.wikipedia.org/wiki/Dioritehttp://en.wikipedia.org/wiki/Diorite > Obsidian - http://en.wikipedia.org/wiki/Obsidianhttp://en.wikipedia.org/wiki/Obsidian > Scoria - http://en.wikipedia.org/wiki/Scoriahttp://en.wikipedia.org/wiki/Scoria > Tuff - http://en.wikipedia.org/wiki/Tuffhttp://en.wikipedia.org/wiki/Tuff Igneous Processes