Metamorphic core of the Himalayan Mountains Rocks~metamorphic rocks form as existing rocks change~ http://www.videojug.com/film/geology-metamorphic-rocks http://www.youtube.com/watch?v=kRUwchlza88
Vocabulary • FOLIATION • Minerals • arranged in flat • or wavy parallel • bands • METAMORPHISM • The process of a rock changing by heat or pressure—or both. • RECRYSTALLIZATION • Heat and pressure break the bonds that join atoms in minerals. Then the atoms join differently, making new minerals.
Heat and Pressure Changes Rocks • Pressure causes minerals to • flatten out in one direction. • Heat and pressure break • bonds between atoms, and • recrystallization occurs. • The higher the temperature • and pressure, the greater the • changes.
How Rocks Change… Increasing Heat & Pressure 1. Sedimentary rock, like shale, can be buried when pushed into the crust. shale 2. Shale changes to slate as pressure causes the minerals to line up in layers. slate 3. Slate changes to phyllite deeper in the crust with higher heat/pressure. phyllite 4. With even more heat and pressure, phyllite changes into schist and new minerals are formed. schist 5. Deep within the crust, schist changes to gneiss. Recrystallization separates light and dark minerals. gneiss Metamorphic rocks form as existing rocks go through metamorphism –heat and pressure
Metamorphic Changes Over Large Areas • Change occurs over large areas when BOTH temperature and pressure forces are high. • Rocks are buried, pressed together, and broken apart. • Occurs over 1,000’s of • kilometers wide and deep. • Mountain ranges can be • made.
Metamorphic Changes Over Small Areas • Change occurs over small areas with high temperature OR high pressure. • Heat from lava or magma can cause rocks to recrystalize. • Pressure can cause rocks to move and grind past each other. • Earthquakes can occur.
Foliated & Nonfoliated Rocks • Foliation develops when rocks are under pressure. • Foliation is common in rocks that have changed over large areas. • If a rock is made of mainly one mineral, it is nonfoliated. There are no minerals to separate and line up in layers. Marble and quartzite are examples of this.