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metamorphic rocks

metamorphic rocks. ESRT page 7. Key ideas. Formed when existing rocks are changed by HEAT & PRESSURE, forming new, larger, denser crystalline structures The new rocks resemble the “parent” rock. Parent rock: Preexisting rock

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metamorphic rocks

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  1. metamorphic rocks ESRT page 7

  2. Key ideas • Formed when existing rocks are changed by HEAT & PRESSURE, forming new, larger, denser crystalline structures • The new rocks resemble the “parent” rock

  3. Parent rock: Preexisting rock • Recrystallization: A process in which rocks undergo change without truly melting

  4. More Key Ideas • IMPORTANT- THE ORIGINAL ROCK CANNOT MELT WHEN IT BECOMES METAMORPHIC! (If it melts, it’s igneous!) • Metamorphism

  5. REGIONAL: Large areas of rock are changed by HEAT & PRESSURE Types of metamorphism

  6. Metamorphic mountains formed from regional metamorphism

  7. CONTACT • Magma touches layers of rock and the HEAT causes the rock layers to change

  8. Alaska’s Copper Mountain – contact metamorphism

  9. the bells & whistles for metamorphic rock identification • BANDING – alternating layers of different colored minerals due to sorting by density • These bands are usually distorted from the heat & pressure • not to be confused with sedimentary layers!!!!!!

  10. Stratification (sed) vs. Banding (metamorphic)

  11. Stratification vs. Banding

  12. FOLIATION • FOLIATION – mineral alignment – the minerals in the rock are layered, which facilitates breakage along flat planes- look for “scratches” in the rocks

  13. More foliation – slate & phyllite Foliation – note the “scratches” in the rock – this is mineral alignment! Excellent example of banding & distortion – this is GNEISS  Banding – mica schist

  14. Difference Between Marble and Quartzite -Both are white in color • Marble reacts with HCl acid and quartzite does not

  15. When I was young, liquid granite I was diagnosed schizophrenic Neither feldspar, nor mica, nor quartz But the sum of the three Bonded igneouslyThat means melted together for life Well, I was hot and dejected Oh, I was injected Under layers and layers of dirt But, it was there that I changed All my crystals rearranged Into G-N-E-I-S-S, gneiss So, take a look, and you'll see That I'm not what I used to be I've been touched metamorphicallyAll the heat and the pressure Have changed me forever So don't take me for granite, I'm gneiss The GNEISS SONG Well, I wasn't to been seen Until time changed the scene Exposing my face to the sun But, now its here that I sit Being worn down bit by bit Oh, erosion is wearing me down Refrain So, be aware, have a look Underground or underfoot For that beautiful pinky-gray face The Canadian shield Holds a magnamous yield Of the rock that was changed into gneiss Refrain

  16. Okay… Let’s sum up!

  17. There are 3 classifications of ROCKS • Igneous – formed by the cooling of magma (melted rock) • Sedimentary – formed by compaction & cementation of rock fragments • Metamorphic – formed by heat & pressure changing existing rocks

  18. Remember the “bells & whistles” when identifying rocks! • Igneous – obvious crystals of different minerals • Sedimentary – stratification, fragments, fossils • Metamorphic – foliation, banding

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