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What is a Rock?

What is a Rock?. A rock is a: Naturally formed, Consolidated material, Composed of grains of one or more minerals. Some Rocks. Types of Common Rocks. There are three types of common rocks: Igneous rock Sedimentary rock Metamorphic rock. Igneous Rock.

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What is a Rock?

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  1. What is a Rock? • A rock is a: • Naturally formed, • Consolidated material, • Composed of grains of one or more minerals.

  2. Some Rocks

  3. Types of Common Rocks • There are three types of common rocks: • Igneous rock • Sedimentary rock • Metamorphic rock

  4. Igneous Rock • Igneous rocks form from the solidification of magma. • Ex: pumice, obsidian

  5. Identifying Igneous Rocks • Where the igneous rock forms in the crust shapes their composition so igneous rocks are identified by their texture. • Extrusive rocks form at or near the surface and are fine-grained. • Intrusive rocks form below the surface and are coarse-grained.

  6. Basalt: Igneous – Extrusive, Fine-grained

  7. Granite: Igneous – Intrusive, Coarse-grained

  8. Igneous Rock Features:Felsic • Felsic rocksare rich in potassium feldspar and quartz and arelight in color. • Example is thegranitefamily of rocks. • Felsic rocksare most common in thecontinents.

  9. Felsic Igneous Rocks

  10. Igneous Rock Features: Mafic • Mafic rocksare rich indarkplagioclase feldspar and pyroxene. • Example thegabbrofamily of rocks. • Mafic rocksare more common in theocean basins.

  11. Mafic Igneous Rocks Basalt

  12. IgneousIdentification • Some igneous rocks have holes in them that formed during the cooling of the magma. These types are said to bevesicular.

  13. Igneous Rocks

  14. Structure of Igneous Rocks • Shield and Cinder Cone volcanoes will erupt and create lava flows, and lava plateaus, that form igneous rocks. • When magma does not erupt but instead forces its way up through cracks and faults it produces large masses of intrusive rock called plutons.

  15. Shield (Etna) and Cinder Cone (Paracutin)

  16. Plutons • Plutons are classified according to size: • Sills are slabs of igneous rock parallel to the rocks they intrude; • Dikes are slabs of igneous rock that cut across the rock layers they intrude; • A laccollith forms between two rock layers, bulging up to form a dome; • A batholith is the largest intrusion and they form the core of many mountain ranges. • When a volcano erodes the harder volcanic neck is often left behind.

  17. Devil’s Tower is the result of igneous rock that was underground until all the weaker surrounding rock was eroded

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