3 4 Metamorphic rocks form as existing rocks

3. 4 Metamorphic rocks form as existing rocks change

Classifying Rocks n 3 rock types Sedimentary n Igneous n Metamorphic n

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

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

Metamorphic

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

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

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

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

Foliated metamorphic rocks Slate Gneiss

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

Non foliated metamorphic Rocks Marble Quartzite

Brain Pop n http: //www. brainpop. com/science/earthsys tem/typesofrocks/preview. weml

Discussion n What is metamorphism? n n 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? n Metamorphic rocks can form due to changes in temperature and pressure.

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

Challenge Refer to book… n Compare and contrast contact metamorphism and regional metamorphism. n n 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.