10/20/2015. How is magma different from lava? Magma is molten rock below the Earth s surface. Lava is magma that flows out onto Earth s surface.

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Chapter 5 What are igneous rocks? How do they form? Igneous rocks are rocks that form when molten material cools and crystallizes. Molten material can be either magma or lava.

1 Chapter 5 What are igneous rocks? How do they form? Igneous rocks are rocks that form when molten material cools and crystallizes. Molten material can be either magma or lava. How is magma different from lava? Magma is molten rock below the Earth s surface. Lava is magma that flows out onto Earth s surface. Igneous rock forms when lava on the surface, or magma below the Earth s surface cools and minerals crystallize. Rocks melt at temperatures of C ( F) Where does this heat come from? The common elements in magma are the same major elements found in the earths crust. O, Si, Al, Fe, Mg, Ca, K, Na The type of magma is dependent on the amount of silica it contains. Group Silica Content Example Location Basaltic 42-52% Hawaiian Islands Andesitic 52-66% Cascade Mountains, Andes Mountains Rhyolitic More than 66% Yellowstone National Park 1

Igneous Rock Forms when magma or lava cools and crystallizes Not all parts of

This explains why magma is often a slushy mix of crystals and molten rock.

2 Igneous Rock Forms when magma or lava cools and crystallizes Not all parts of a rock melt at the same temperature. This explains why magma is often a slushy mix of crystals and molten rock. Quartz =1713 C Calcite =1612 C Halite = 801 C At 1680 C, which minerals would be liquid? When magma cools, it crystallizes in the reverse order of partial melting. This process is called Fractional Crystallization. Minerals with the highest melting points crystallize first. 2

3 Igneous rocks are broadly classified as intrusive or extrusive. Intrusive rock forms when magma cools and crystallizes below Earth s Surface. 3

Intrusive (plutonic) Magma cools slowly below the surface Large crystals (most crystals > 1mm) Extrusive rock forms when magma cools and crystalizes on Earth s

Coarse-grained igneous rock Extrusive (volcanic) Lava cools quickly on the surface Small crystals (most crystals < 1mm) Granite Examples Basalt Igneous rocks are

4 Intrusive (plutonic) Magma cools slowly below the surface Large crystals (most crystals > 1mm) Extrusive rock forms when magma cools and crystalizes on Earth s Surface. Extrusive igneous rock has much smaller crystals due to its fast rate of cooling. Coarse-grained igneous rock Extrusive (volcanic) Lava cools quickly on the surface Small crystals (most crystals < 1mm) Granite Examples Basalt Igneous rocks are also classified according to their mineral composition. Basaltic Rocks are dark colored and have lower silica content. (Mafic) Granitic Rocks are light colored rocks, which have a high silica content, and contain mostly quartz. (Felsic) 4

5 Granitic = Felsic = High Silica content Basaltic = Basic = Mafic = low silica content Texture refers to the size, shape, and distribution of the crystals or grains that make up a rock. Fine-grained, coarse grained, ect. Porphyritic Texture: characterized by large, well formed crystals, surrounded by finergrained crystals of the same or different mineral. 5

6 Vesicular Texture: Exhibits a spongy appearance. Forms when dissolved gasses in magma escape when the pressure on the magma lessens. Pegmatites Pegmatites: Pegmatites are veins of extremely large-grained minerals that flow through igneous rock. Kimberlite: Rare, ultramafic rock that can contain diamonds and other minerals formed only under very high pressure. Named after Kimberly, South Africa 6

7 Chapter 5 1. A is a natural inorganic crystalline solid with a characteristic chemical composition. a. atom b. mineral c. rock 1. A is a natural inorganic crystalline solid with a characteristic chemical composition. a. atom b. mineral c. rock 1. Igneous Rocks that forms below Earth's surface are called: c. Mafic d. Felsic 7

8 1. Igneous Rocks that forms below Earth's surface are called: c. Mafic d. felsic 1. These Igneous Rocks form on Earth's surface - they usually come out of volcanoes. c. Felsic d. Mafic 1. These Igneous Rocks form on Earth's surface - they usually come out of volcanoes. c. Felsic d. Mafic 1. Granite formed underground, therefore granite has crystals. a. large b. small c. no 1. Granite formed underground, therefore granite has crystals. a. large b. small c. no 1. Which of the following are the major categories of rock found on Earth? a. Igneous, Sedimentary, Metamorphic b. Granite, Basalt, Limestone c. Mafic, Intrusive, Batholith 8

9 1. Which of the following are the major categories of rock found on Earth? a. Igneous, Sedimentary, Metamorphic b. Granite, Basalt, Limestone c. Mafic, Intrusive, Batholith 1. rock is formed from existing rock through the action of heat and pressure. a. Igneous b. Metamorphic c. Sedimentary 1. rock is formed from existing rock through the action of heat and pressure. a. Igneous b. Metamorphic c. Sedimentary 1. You find a piece of quartz with very large crystals. Based on your observation, you infer that the rock formed: a. above ground b. underground c. is a meteorite 1. You find a piece of quartz with very large crystals. Based on your observation, you infer that the rock formed: a. above ground b. underground c. is a meteorite 1. Giant's causeway in Ireland formed from a volcanic eruption about 60 million years ago. Based on this knowledge, you infer that these rocks are: c. They formed too long ago to know what type they are. 9

10 1. Giant's causeway in Ireland formed from a volcanic eruption about 60 million years ago. Based on this knowledge, you infer that these rocks are: c. They formed too long ago to know what type they are. 1. What is Porphyritic? 2. What is partial melting? 3. Name two common elements that are present in magma that are the same major elements that are found in Earths crust. oxygen, silicon, aluminum, iron, magnesium, sodium, calcium, potassium 4. True or False: All igneous rocks have crystals. 5. True or false: Igneous rocks are rocks that form when molten material cools and crystalizes. 6. Basaltic rock contains a low silica content. True or false? 7. forms when magma flows on the Earth s surface. 8. True or false: Pumice cannot float. 9. Describe Granitic rock. 10.What is the difference between intrusive and extrusive igneous rock? 1. Gases escape from as it flows out onto earths surface. 2. forms deep beneath Earth s crust 3. An igneous texture characterized by large crystals embedded in a fine-grained background is called a. 1. Igneous rocks that form under conditions of fast cooling are said to be. 2. Light-colored rocks with large crystals are said to be. 10

11 1. What type of magma contains the greatest amount of silica? 1. Basaltic 2. Andesitic 3. Rhyolitic 4. Peridotic 1. What type of magma contains the greatest amount of silica? 1. Basaltic 2. Andesitic 3.Rhyolitic 4. Peridotic 1. Which does not affect the formation of magma? 1. Volume 2. Temperature 3. Pressure 4. Mineral Composition 1. Which does not affect the formation of magma? 1.Volume 2. Temperature 3. Pressure 4. Mineral Composition 11

Name Class Date STUDY GUIDE FOR CONTENT MASTERY

Name Class Date STUDY GUIDE FOR CONTENT MASTERY Igneous Rocks What are igneous rocks? In your textbook, read about the nature of igneous rocks. Use each of the terms below just once to complete the following statements. extrusive igneous rock intrusive