3.4 Metamorphic Rocks Metamorphism – “to change form” I Formation of Metamorphic Rocks - Most changes occur at high temperatures and pressures a few km below the Earth’s surface Gneiss Rock A Contact Metamorphism – hot magma moves into rock B Regional Metamorphism – results in large-scale deformation and high-grade metamorphism II Agents of Metamorphism *A Heat – The most important agent Provides the energy needed to drive chemical reactions - The heat comes from magma and the change in temperature with depth *B Pressure (Stress) – Causes a more compact rock with greater density Origin of Pressure in Metamorphism • III Classification of Metamorphic Rocks Can be classified by texture and composition A Foliated Metamorphic Rocks - rock has a layered or banded appearance Ex: Gneiss & Schist Gneiss Typically Displays a Banded Appearance B Nonfoliated Metamorphic Rocks – - Does not have a banded texture - Most only contain one mineral Ex: Marble (calcite) parent rock = limestone & Quartzite Marble Marble - A Nonfoliated Metamorphic Rock • http://www.phschool.com/webcodes10/index.cfm?fuseaction =home.gotoWebCode&wcprefix=cuk&wcsuffix=9999