Metamorphic rocks form deep underground through heat and pressure that alter existing rock. There are two types of metamorphism - regional, which affects large areas of crust over time, and contact, where intruding magma quickly alters surrounding rock. Heat within the Earth comes from radioactive decay in the core. Metamorphism can also be caused by hydrothermal fluids that change rock chemistry and mineralogy, sometimes forming valuable ore deposits. Metamorphic rocks exhibit different textures based on their mineral grain size and alignment.

1. Metamorphic Rocks by Annie Cloutier copyright 2011

2. Pressure and heat increase with depth Pressure and heat inside the Earth cause the changes to occur in rock Where does the heat come from ? Earth generates heat from the radioactive core working its way up to the lithosphere Metamorphic Greek word origin meta means “change” morph means “form”

3. Two Types of Metamorphic Groups Regional metamorphism > when high temperatures and pressure affect large regions of Earth’s crust belts of metamorphic rock happen Contact metamorphism > when molten rock comes in contact with solid rock, large scale minerals change with little deformation

4. Regional Metamorphism

5. Contact metamorphism

6. Cause & Effect of Metamorphism

7. Hydrothermal Metamorphism when very hot water reacts with rock and alters its chemistry and mineralogy

8. Getting into hot water can be good hydrothermal fluids invade the surrounding rocks and change their mineralogy, textures and chemistry valuable ore deposits of gold , copper, silver, tungsten and lead are formed this way

9. Two Textures of Metamorphic Rocks foliated wavy lines, bands, layers characterize foliated rocks; often have small crystals of mineral grains, and long axis of parallel alignment Schist Gneiss Shale nonfoliated usually form with blocky crystal shapes; sometimes record faint color ripple marks Quartzite Marble Calcite

10. Gneiss > Schist > < Slate >

11. It’s Morphing time.. Metamorphic Rock Gneiss < Marble < Slate < Mica schist < Parent Rock Granite Limestone Shale Mica pegmatite Its Morphin’ time !

12. The Rock Cycle

13. The end is not…it’s all a cycle

14. … but this is the end of the power point