Earth Materials Topic 3. Metamorphic rocks Web addressed for pictures are in the notes section.

Metamorphic Rocks are ‘changed’ rocks They can form from any other rock or rock type. http://web.ics.purdue.edu/~braile/edumod/pebble/pebbleAM.htm

Metamorphic Rocks are formed from: a. Heat: contact metamorphism When magma ‘bakes’ a nearby rock. (at volcanoes, mid-ocean ridges, igneous intrusions) http://www.windows2universe.org/earth/geology/meta_contact.html

b. Chemical changes: At mid-ocean ridges when seawater and sediments mix with hot gases

c. Pressure: Regional Metamorphism Occurs in 3 environments: At subducting boundaries when rock is ground and deformed http://gomyclass.com/geology10/files/lecture7/html/web_data/file77.htm

When mountains form by tension, compression http://mtweb.mtsu.edu/cribb/1030metamorphicrocks.html

Overlying sediments exert so much pressure they change the deep rock http://movingtoward.com/morphrocks.htm and http://www.msnucleus.org/membership/html/jh/earth/metamorphic/lesson4/metamorphic4a.html

http://www.indiana.edu/~geol116/week3/week3.htm

http://www.geologycafe.com/class/chapter8.html

1. Metamorphic rocks form: when pre-existing rocks are changed due to heat and pressure. (If the old rock melts, then it does not become metamorphic, because melted rock produces magma and igneous rock).

2.   Metamorphic rocks are recrystallized/ altered versions of pre-existing rock. The minerals often just line up differently, but intense metamorphism will cause new minerals to form. http://imnh.isu.edu/Exhibits/Online/RLO/GeoOutreach/index.php?r=rockinternal&s=metamorphic

http://www. geo. cornell http://www.geo.cornell.edu/eas/education/course/descr/EAS302/302Syllabus06revised.html

3. Metamorphic rock are classified according to: The presence or type of foliation, which is seen by observing the texture of the rock.

b. The second identifier is the mineral composition when discussing the nonfoliated rocks. For example, marble and quartzite look a lot alike, but are made of very different minerals. http://www.geosci.ipfw.edu/PhysSys/Unit_4/metam.html and http://www.studyblue.com/notes/note/n/mineral-and-rocks-geology-lab/deck/3130259

Nonfoliated rocks: composition Ex. Quartzite and marble (the acid test identifies marble and hardness shows which is quartzite). http://www.rocksandminerals4u.com/quartzite.html and http://www.npenn.org/page/5061

a. Texture: foliation or banding The foliated rocks: a. Texture: foliation or banding http://www.columbia.edu/~vjd1/meta_rx.htm

4. Rocks formed by intense pressure from regional metamorphism; minerals align to the direction of the pressure. This often forms the foliated texture. http://www.geosci.ipfw.edu/PhysSys/Unit_4/metam.html and http://www.indiana.edu/~geol105/1425chap5.htm

5. Rocks formed by intense heat are contact metamorphic rocks: Because they are usually bands of rock that are recrystallized due to the presence of nearby lava or magma flows, which partially melt the rock. http://volcano.oregonstate.edu/vwdocs/vwlessons/lessons/Metrocks/Metrocks4.html

7 Contact metamorphic rock are found along igneous intrusions where the magma heats the rock. do not show foliation. http://www.columbia.edu/~vjd1/meta_rx.htm

Contact metamorphic rocks Zones of metamorphic rocks usually are found between igneous rocks and other rocks.

Types of foliation in ESRT Banding: ribbons of different minerals Mica in the rock indicates regional metamorphism http://geology.about.com/od/rocks/ig/metrockindex/rocpicschist.htm