3.4 Metamorphic rocks form as existing rocks change

Classifying Rocks 3 rock types Sedimentary Igneous Metamorphic

Metamorphism The process by which existing rock is changed by pressure or heat

Metamorphic Rocks “change” Igneous and sedimentary rocks that have changed due to heat and pressure Heat and pressure cause new combinations or new crystals to form **heating and cooling of in mantle layer may lead to this formation

Metamorphic

Parent Rock The original rock went through metamorphism. (the rock changed) Ex: igneous rock and sedimentary rock “melting” together to form this new metamorphic rock) A metamorphic rock CAN be a parent to another metamorphic rock One rock, “melting” and turning into another

Changes in Metamorphism Rocks may flatten and pushed together Rocks may “melt” together to form new rocks

Recrystallization The process by which bonds between atoms in minerals break and re-form in new ways during metamorphism

Bands in Rocks Foliation: the arrangement of minerals in flat or wavy parallel bands. Found in rocks made of 2 or more minerals

Foliated metamorphic rocks Slate Gneiss

Nonfoliated Rock Metamorphic rock without foliation (bands/stripes) Primarily made of 1 mineral Not subject to high pressure

Non foliated metamorphic Rocks Marble Quartzite

Brain Pop http://www.brainpop.com/science/earthsystem/typesofrocks/preview.weml

Discussion What is metamorphism? It is any process that affects the structure or composition of a rock in a solid state as a result of changes in temperature, pressure, or the addition of chemical fluids. Under what conditions do metamorphic rocks form? Metamorphic rocks can form due to changes in temperature and pressure.

Discussion What type of metamorphic rock has layers? Foliated metamorphic rock has layers (stripes).

Challenge Refer to book… Compare and contrast contact metamorphism and regional metamorphism. Contact metamorphism occurs where magma comes in contact with parent rock. Regional metamorphism occurs over a much larger area and results from increases in pressure and temperature and chemical fluids.