1. Mrs. Hutson

2.   Igneous rock forms when hot, liquid rock, or magma, cools and solidifies.  The type of igneous rock that forms depends on the composition of the magma and the amount of time it takes the magma to cool. What is Igneous Rock?

3.   Igneous rock begins as magma.  There are three ways magma can form:  when rock is heated  when pressure is released  when rock changes composition. Origins of Igneous Rock

4.   Which of the following are ways magma is formed?  A. By compaction and cementation  B. By melting and cooling  C. By changes in composition  D. By weathering and erosion Think about it!

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6.   When magma cools enough, it solidifies to form igneous rock.  Magma solidifies in much the same way that water freezes.  Magma contain many different types of minerals, some minerals in the magma will freeze or become solid before other minerals do. Magma can Solidify

7.   Let’s look at the rocks in Figure 2.  All of the rocks are igneous rocks even though they look different from one another.  These rocks differ from one another in what they are made of and how fast they cooled. Composition and Texture of Igneous Rock

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9.   The light-colored rocks are less dense than the dark- colored rocks are.  The light-colored rocks are rich in elements such as aluminum, potassium, silicon, and sodium.  These rocks are called felsic rocks. The dark-colored rocks, called mafic rocks, are rich in calcium, iron, and magnesium, and poor in silicon. Composition Continued

10.   Figure 3 shows what happens to magma when it cools at different rates.  The longer it takes for the magma or lava to cool, the more time mineral crystals have to grow.  The more time the crystals have to grow, the larger the crystals are and the coarser the texture of the resulting igneous rock is

11.   What kind of texture does igneous rock have when magma cools slowly?  A. Coarse-grained  B. Large-grained  C. Fine-grained  D. Medium-grained Think about it!

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13.   Figure 3 should us what?  The amount of time it takes for magma or lava to cool determines the texture of igneous rock.  The less time magma takes to cool, the less time crystals have to grow. Therefore, the rock that is formed will be fine grained.

14.   What kind of texture does igneous rock have when magma cools rapidly?  A. Coarse-grained  B. Medium-grained  C. Fine-grained  D. Large-grained Think about it!

15.   Igneous rock formations are located above and below the surface of the Earth.  You may be familiar with igneous rock formations that were caused by lava cooling on the Earth’s surface, such as volcanoes.  But not all magma reaches the surface. Some magma cools and solidifies deep within the Earth’s crust Igneous Rock Formations Above and Below the Earth’s Surface

16.   When magma intrudes, or pushes, into surrounding rock below the Earth’s surface and cools, the rock that forms is called intrusive igneous rock.  Intrusive igneous rock usually has a coarse- grained texture because it is well insulated by surrounding rock and cools very slowly. The minerals that form are large, visible crystals. Intrusive Igneous Rock

17.   Igneous rock that forms from magma that erupts, or extrudes, onto the Earth’s surface is called extrusive igneous rock.  Extrusive rock is common around volcanoes. It cools quickly on the surface and contains very small crystals or no crystals. Extrusive Igneous Rock

18.   What kind of rock is formed when magma intrudes into other rock?  A. Extrusive igneous rock  B. Sedimentary rock  C. Intrusive igneous rock  D. Organic sedimentary rock Think about it!

19.   What kind of rock is formed from lava that cools on the Earth’s surface?  A. Organic sedimentary rock  B. Sedimentary rock  C. Intrusive igneous rock  D. Extrusive igneous rock Think about it!

20.   Igneous rock forms when magma cools and hardens.  The texture of igneous rock is determined by the rate at which the rock cools.  Igneous rock that solidifies at Earth’s surface is extrusive. Igneous rock that solidifies within Earth’s surface is intrusive.  Shapes of common igneous intrusive bodies include batholiths, stocks, sills, and dikes. Section Summary