METAMORPHIC ROCKS Rocks that form from other preexisting

METAMORPHIC ROCKS Rocks that form from other pre-existing rock (sedimentary, igneous, or metamorphic) that have been changed from high temperature and/or high pressure

Metamorphic Rocks

Metamorphic Rocks Formation

Conditions that cause rock to undergo metamorphism include: • Heat - Under conditions of high temperature from magma contacting pre-existing rock. • Pressure - Deep burial and pressure from mountain formation.

Types of Metamorphism 1. Contact Metamorphism 2. Regional Metamorphism

Contact Metamorphism Deep burial and pressure from mountain formation. The main metamorphic agent is heat. Also forms when pre-existing rock comes into contact with molten lava or magma. The heat from the molten material is hot enough to cause the minerals in the original rock to re-crystallize, but not melt.

Regional Metamorphism Covers large areas typically associated with mountains Deep burial and pressure from mountain formation. Heat and Pressure change the rock

Types of Metamorphic Rocks Foliated: rocks with mineral crystals arranged in cable-like distorted layers/structures Mineral Alignment Banding Animation: Foliation Nonfoliated: rocks with recrystallized minerals; no layering Recrystallization: This is the growth of new mineral crystals from other rocks.

Scheme for Metamorphic Rock Identification Texture Composition MINERAL ALIGNMENT BANDING FOLIATED Mica, Quartz, Feldspar, Amphiboles, Garnet, Pyroxene Type of Metamorphism Comment Rock Name Regional Low-Grade metamorphism of SHALE Slate (Heat and Pressure increase w/ depth) Foliation surfaces shiny from microscopic mica crystals Platy mica crystals visible Compact, may split easily Phyllite Schist Gneiss

Progression of Metamorphism Start with a shale and then hit it with heat and pressure! More Heat & Pressure Rock Name Rock Type Grade of Metamorphism Shale Sedimentary ----- Slate Metamorphic Low Phyllite Metamorphic Low/Intermediate Schist Metamorphic Intermediate/High Gneiss Metamorphic High Molten Rock Cools into Igneous Rock -----

Shale (Sedimentary Rock) Heat & Pressure Slate (Metamorphic Rock)

Slate (Metamorphic Rock) Heat & Pressure Phyllite (Metamorphic Rock)

Phyllite (Metamorphic Rock) Heat & Pressure Schist (Metamorphic Rock)

With even more heat & pressure (High-Grade Metamorphism) … you end up with something that is really Gneiss!

Scheme for Metamorphic Rock Identification Texture Composition NONFOLIATED Variable Type of Metamorphism Contact (Heat) Quartz Regional Calcite and/or Dolomite (Heat & Pressure) Various minerals in particles and matrix Comment Various rocks changed by nearby magma/lava Metamorphism of Quartz Sandstone Metamorphism of Limestone or Dolostone Rock Name Hornfels Quartzite Marble Pebbles may be distorted or stretched Metaconglomerate

ESRT p. 7 Animation: Metamorphic Rock Scheme

Where are metamorphic rocks found? At the interface between igneous and sedimentary rocks • Mountainous regions

THE ROCK CYCLE How are rocks classified?

How are rocks classified? By their origin (the way they are formed)

Major Rock Groups Sedimentary Formed at the Earth’s surface Clastic (Mineral Fragments or grains, clays) Crystalline (chemical precipitates and evaporites) Bioclastic (formed organically from shells or plants) Igneous Formed from magma (molten rock) Plutonic (intrusive): slow cooling, coarse/very coarse crystals Volcanic (extrusion): quick cooling at the surface, glassy/fine crystals Metamorphic Changed by heat and pressure

Rock Cycle Conclusion

Fig. 2. 9 MAGMA

IGNEOUS Solidification MAGMA

IGNEOUS Plutonic Solidification MAGMA

Volcanic IGNEOUS Plutonic Solidification MAGMA

Weathering & Erosion Uplift Volcanic IGNEOUS Plutonic Solidification MAGMA

SEDIMENT Weathering & Erosion Volcanic IGNEOUS Plutonic Solidification MAGMA

SEDIMENT Weathering & Erosion Transport Deposition Volcanic SEDIMENTARY IGNEOUS Plutonic Solidification MAGMA

SEDIMENT Weathering & Erosion Deposition Burial/Compaction Cementation Volcanic SEDIMENTARY IGNEOUS Plutonic Solidification MAGMA

SEDIMENT Weathering & Erosion Deposition Burial/Compaction Cementation Volcanic SEDIMENTARY IGNEOUS Plutonic Increased P&T METAMORPHIC Solidification MAGMA

SEDIMENT Weathering & Erosion Deposition Burial/Compaction Volcanic Can you see IGNEOUS any shortcuts? Cementation SEDIMENTARY Plutonic Increased P&T METAMORPHIC Solidification Melting MAGMA

SEDIMENT Weathering & Erosion Deposition Burial/Compaction Cementation Volcanic SEDIMENTARY IGNEOUS Plutonic Increased P&T METAMORPHIC Solidification Melting MAGMA

SEDIMENT Weathering & Erosion Deposition Burial/Compaction Cementation Volcanic SEDIMENTARY IGNEOUS Plutonic Increased P&T METAMORPHIC Solidification Melting MAGMA

Citations Slide 6 (Progression of Metamorphism of Shale) http: //physics. uwstout. edu/geo/_derived/sect 4. htm_txt_sect 4. 2. gif Slide 10 Shale: http: //library. thinkquest. org/06 aug/02459/rocks/sedimentary/Shale. jpg Slate: http: //www. global-b 2 b-network. com/direct/dbimage/10260661/Grey_Slate. jpg Slide 11: Phyllite: http: //www. bedford. k 12. ny. us/flhs/science/geoscience/images/phyllite. jpg Slide 12: Schist (1) http: //www. randall. k 12. wi. us/rocks/images/schist-with-garnet. jpg Schist (2) http: //www. es. ucl. ac. uk/schools/Glossary/schist. jpg Slide 13: Gneiss (1) http: //hyperphysics. phy-astr. gsu. edu/hbase/geophys/geopic/gneiss 2. jpg Gneiss (2) http: //www. cropsoil. uga. edu/soilsandhydrology/images/Gneiss. jpg Gneiss (3) http: //upload. wikimedia. org/wikipedia/commons/6/60/Gneiss. jpg Slide 16: 8/16/2006 Physical Setting Regents Earth Science Exam p. 18 Slide 17: Earth Science Reference Tables p. 6