1. Igneous Rock 12/1/14 4-2 pgs. 87-90 IN: Explain, using words and pictures, how rocks form.

2. sedimentary rock sediment magma cooling, crystallization weathering and erosion compaction, cementation melting high temperature great pressure igneous rock metamorphic rock

4. How are igneous rock formed? Rocks are heated enough to melt its minerals into magma. Magma cools into various types of igneous rock depending on the composition of the magma and the amount of time it takes the magma to cool and solidify.

5. How are igneous rock classified? Like all other rock, igneous rock is classified according to its composition and texture.

6. How does magma form? Temperature An increase in temperature deep within the Earth’s crust can cause the minerals in a rock to melt. Different minerals melt at different temperatures, from about 700 to 1250 degrees Celsius.

7. How does magma form? Pressure The high pressure deep within the earth forces minerals to stay in the solid state, so when hot rocks rise to shallow depths the pressure is released and they melt.

8. How does magma form? Composition Sometimes fluids like water and carbon dioxide enter a rock that is close to its melting point. Remember, water melts above 0 degrees Celsius and carbon dioxide melts above -78 degrees Celsius.

9. Composition Felsic - light-colored (Light as a Feather) Less dense…light Rich in elements such as silicon, aluminum, sodium and potassium. Granite, Obsidian, Pumice

10. Composition Mafic - dark-colored (dark as Midnight) More dense…heavy Rich in elements such as iron, magnesium, and calcium Basalt

11. Texture Intrusive Igneous Rock When magma cools beneath the Earth’s surface. Coarse-grained texture Cools slowly Granite & Basalt (because the pressure of the ocean makes the crystals small)

12. Big amount of time=Big crystals=Coarse Grain

13. Texture Extrusive Igneous Rock When lava cools on the Earth’s surface. Fine-grained texture Cools quickly Small amount of time= small crystals Pumice & Obsidian

14. Granite Igneous plutonic rock formed when magma cools slowly. Remember it’s made up of mica, feldspar, and quartz...all silicates. Felsic Intrusive Coarse-grained

15. Basalt Igneous volcanic rock with small crystals made when lava cools. Mafic Intrusive/Extrusive Fine-grained

16. Obsidian Igneous rock formed from volcanoes that has sharp edges and looks like glass. Felsic Extrusive Fine-grained

17. Pumice Igneous rock with holes and can float on water. Felsic Extrusive Coarse-grained

18. OUT: What are some features of igneous rocks?