1. Igneous Rocks

2. The Nature of Igneous Rocks All igneous rocks are made of interlocking crystals of minerals that cool and crystallize our of magma. All igneous rocks are made of interlocking crystals of minerals that cool and crystallize our of magma. Minerals are compounds of chemical elements. Minerals are compounds of chemical elements. There are 6 types of minerals that are common in igneous rocks. They are: quartz, micas, feldspars, pyroxenes, amphiboles, and olivines. There are 6 types of minerals that are common in igneous rocks. They are: quartz, micas, feldspars, pyroxenes, amphiboles, and olivines. Magma – It is a natural occurring molten rock material, generated within the Earth, from which igneous rocks are formed from. Magma – It is a natural occurring molten rock material, generated within the Earth, from which igneous rocks are formed from.

3. Magma, Lava, and Igneous Rock Every kilometer into the earth you go, the temperature goes up about 30 degrees Celsius. Every kilometer into the earth you go, the temperature goes up about 30 degrees Celsius. At about 100 km to 350 km into the Earth, the temperature is great enough to melt rock, and this melted rock is magma. At about 100 km to 350 km into the Earth, the temperature is great enough to melt rock, and this melted rock is magma. Magma is less dense than the rock around it, so it rises, like a hot air balloon. Magma is less dense than the rock around it, so it rises, like a hot air balloon. Remember hot is less dense than cold, that is why hot air rises. Remember hot is less dense than cold, that is why hot air rises.

4. Intrusive Igneous Rock This type of rock forms underneath the surface of the Earth. This type of rock forms underneath the surface of the Earth. It is called “Intrusive” because the magma intrudes into rock that is already there. It is called “Intrusive” because the magma intrudes into rock that is already there.

5. Extrusive Igneous Rock When magma cools on the surface, it is called extrusive igneous rock, because the magma (now called lava since it is on the surface) “extruded” onto the Earth’s surface like toothpaste from a tube. When magma cools on the surface, it is called extrusive igneous rock, because the magma (now called lava since it is on the surface) “extruded” onto the Earth’s surface like toothpaste from a tube.

6. How to classify Igneous Rocks There are two ways to classify igneous rocks: There are two ways to classify igneous rocks: Color Color Texture TextureColor The minerals inside an igneous rock determine the color. Light color minerals are: quartz, feldspar, and mica. Dark color minerals tend to be pyroxenes, amphiboles, feldspar, mica, and olivines.

7. How to classify Igneous Rocks Texture Texture The crystal size of an igneous rock depends on how fast or slow the magma cools. The crystal size of an igneous rock depends on how fast or slow the magma cools. Slow cooling magma means large crystals Slow cooling magma means large crystals Fast cooling magma means many small crystals Fast cooling magma means many small crystals If lava cools really fast, it may result in a glassy looking rock. If lava cools really fast, it may result in a glassy looking rock.

8. Lithospheric Plates and Igneous Rocks Lithospheric Plates – a rigid, thin segment of the outermost layer of the Earth, consisting of the Earth’s crust and part of the upper mantle. The plate can be assumed to move. Lithospheric Plates – a rigid, thin segment of the outermost layer of the Earth, consisting of the Earth’s crust and part of the upper mantle. The plate can be assumed to move. Convergent Boundary – A boundary line where lithospheric plates are moving towards each other. Convergent Boundary – A boundary line where lithospheric plates are moving towards each other. Divergent Boundary – A boundary line that is getting wider as lithospheric plates move away from each other. Divergent Boundary – A boundary line that is getting wider as lithospheric plates move away from each other. Transform Boundary – A boundary line where two lithospheric plates are sliding past each other. Like two cars on a road. Transform Boundary – A boundary line where two lithospheric plates are sliding past each other. Like two cars on a road.