Presentation on theme: "METAMORPHIC ROCKS Rocks that form from other pre-existing rock (sedimentary, igneous, or metamorphic) that have been changed from high temperature and/or."— Presentation transcript:
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
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 Animation: Foliation Nonfoliated: rocks with recrystallized minerals; no layering Recrystallization: This is the growth of new mineral crystals from other rocks.
TextureComposition Type of Metamorphism CommentRock Name Mica Regional (Heat and Pressure increase w/ depth) Low-Grade metamorphism of SHALE Mica, Quartz, Feldspar, Amphiboles, Garnet Foliation surfaces shiny from microscopic mica crystals Mica, Quartz, Feldspar, Amphiboles, Garnet, Pyroxene Platy mica crystals visible Mica, Quartz, Feldspar, Amphiboles, Garnet, Pyroxene Compact, may split easily FOLIATED MINERAL ALIGNMENT BAND- ING Scheme for Metamorphic Rock Identification Slate Phyllite Gneiss Schist
Progression of Metamorphism Start with a shale and then hit it with heat and pressure! Rock NameRock Type Grade of Metamorphism ShaleSedimentary----- SlateMetamorphicLow PhylliteMetamorphic Low/Intermediate SchistMetamorphic Intermediate/High GneissMetamorphicHigh Molten Rock Cools into Igneous Rock ----- More Heat & Pressure
With even more heat & pressure (High-Grade Metamorphism) … you end up with something that is really Gneiss!
Scheme for Metamorphic Rock Identification TextureComposition Type of Metamorphism CommentRock Name Variable Contact (Heat) Various rocks changed by nearby magma/lava Quartz Metamorphism of Quartz Calcite and/or Dolomite Metamorphism of Various minerals in particles and matrix Pebbles may be distorted or stretched NONFOLIATED Regional (Heat & Pressure) Sandstone Limestone or Dolostone Hornfels Quartzite Marble Metaconglomerate
ESRT p. 7 Animation: Metamorphic Rock Scheme Animation: Metamorphic Rock Scheme
Where are metamorphic rocks found? At the interface between igneous and sedimentary rocks Mountainous regions
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