What is a rock? A rock is a combination of minerals. For example: Granite is composed of biotite, quartz, and feldspar.

The Rock Cycle Any rock can be changed into any other type of rock. Metamorphic Rocks The Rock Cycle Any rock can be changed into any other type of rock. The rock cycle is the continuous changing and remaking of rocks.

The Rock Cycle Igneous and sedimentary rocks may be transformed by heat, pressure and chemical reactions into metamorphic rocks. Metamorphic rocks may be changed or metamorphosed into other metamorphic rocks. They may also be remelted into and igneous rock. Or a metamorphic rock can be weathered to form a sedimentary rock. Any rock can be changed into any other type of rock.

Other Possible Paths There is more than one path in the rock cycle. Metamorphic Rocks Other Possible Paths There is more than one path in the rock cycle. The rocks of Earth’s crust are constantly being recycled from one type to another. The processes that help shape Earth’s landscapes are also part of the rock cycle.

What are igneous rocks? What are igneous rocks? About 95% of rocks on the earth are igneous or metamorphic although mostly sedimentary cover the surface due to weathering and erosion. Igneous rocks are rocks are formed from volcanoes Igneous rocks are formed from the crystallization of magma

What are igneous rocks? Types of Igneous Rocks Intrusive igneous rocks are coarse-grained igneous rocks that cool slowly beneath Earth’s surface. (INside the earth) Granite is the most common intrusive igneous rock. Extrusive igneous rocks are fine-grained igneous rocks that cool quickly on Earth’s surface. (Ex=Out of) An example is basalt or obsidian.

What are igneous rocks? Types of Igneous Rocks Careful study of granite rock formations revealed that they cut across other rock formations. These cross-cutting relationships are evidence that the granite was intruded, or forced into, existing rocks. Magma cools slowly beneath Earth’s surface and forms course-grained igneous rocks such as granite.

What are igneous rocks? Composition of Magma Magma is often a slushy mix of molten rock, gases, and mineral crystals. The elements found in magma are the same major elements found in Earth’s crust: oxygen (O), silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), calcium (Ca), potassium (K), and sodium (Na).

Classifying Igneous Rocks Igneous rocks are broadly classified as intrusive or extrusive. Igneous rocks are further classified by their mineral compositions and texture. Composition refers to the minerals that make up a rock.

Classifying Igneous Rocks Mineral Composition The two main groups of igneous rocks are felsic and mafic are classified according to their mineral compositions. Felsic rocks, such as granite, are light-colored and have high silica contents. (L=Light!) Mafic rocks, such as gabbro, are dark-colored, have lower silica contents, and are rich in iron and magnesium.

Classifying Igneous Rocks Grain Size In addition to differences in their mineral compositions, igneous rocks differ in the sizes of their grains. Cooling Rates When lava flows on Earth’s surface, it cools quickly and there is not enough time for large crystals to form. Extrusive igneous rocks have no visible mineral grains. When magma cools slowly beneath Earth’s surface, there is sufficient time for large crystals to form. Intrusive igneous rocks may have crystals larger than 1 cm.

Classifying Igneous Rocks Texture Often, it’s easier to observe the sizes of mineral grains than it is to observe their shapes. Many mineral grains have interlocking edges. As the grains crystallize from magma, they grow together and form irregular edges. Texture gives clues for the identification of various igneous rocks. Texture is the size, shape, arrangement and distribution of minerals in the rock.

Glassy Texture An example of glassy texture is obsidian.

Fine grained texture An example of fine grained is basalt or gabbro.

Coarse grained texture An example is granite.

Texture Porphyritic Texture Classifying Igneous Rocks Texture Porphyritic Texture A rock that has a porphyritic texture is characterized by large crystals surrounded by finer-grained crystals. Porphyritic textures indicate a complex cooling history wherein a slowly cooling magma suddenly began cooling rapidly.

Pumice Pumice can float! Pumice is used as an abrasive cleaner.

More Uses of Igneous Rocks

Uses of Igneous rocks- granite countertops

Scoria is a landscaping material

Igneous Rocks Igneous rock - Wikipedia, the free encyclopedia

Metamorphic Rocks Metamorphic rock - Wikipedia, the free encyclopedia

Uses of Metamorphic Rocks Marble chips for landscaping

Igneous Rocks as Resources Classifying Igneous Rocks Igneous Rocks as Resources Igneous rocks have several characteristics that make them especially useful as building materials. The interlocking grain textures of igneous rocks help to give them strength. Many of the minerals found in igneous rocks are resistant to weathering.

Classifying Igneous Rocks Ore Deposits Ores are minerals that contain a useful substance that can be mined at a profit. Valuable ore deposits are often associated with igneous intrusions. These deposits sometimes occur as veins.

Classifying Igneous Rocks Section Assessment 1. Match the following terms with their definitions. ___ felsic ___ mafic ___ ultramafic ___ porphyritic B D A C A. igneous rocks that have low silica content and very high levels of iron and magnesium B. igneous rocks that are light-colored, have high silica contents, and contain quartz and feldspars C. texture characterized by well-formed crystals surrounded by finer-grained crystals D. igneous rocks that are dark-colored, have lower silica contents, and are rich in iron and magnesium

End of Section 2

Chapter Resources Menu Study Guide Section 5.1 Section 5.2 Chapter Assessment Image Bank Chapter Resources Menu

Section 5.1 Study Guide Section 5.1 Main Ideas Igneous rocks are formed by the cooling and crystallization of magma. Intrusive rocks form inside Earth’s crust, and extrusive rocks form on Earth’s surface. Extrusive rocks, which cool more rapidly than intrusive rocks, are generally more fine grained. Magma is a slushy mix of molten rock, gases, and mineral crystals. The elements found in magma are the same major elements found in Earth’s crust: oxygen (O), silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), calcium (Ca), potassium (K), and sodium (Na).

Section 5.1 Study Guide Section 5.1 Main Ideas Silica (SiO2) is the most abundant compound in magma. Magmas are classified as basaltic, andesitic, and rhyolitic, based on the amount of SiO2 they contain. Different minerals melt and crystallize at different temperatures in the processes of partial melting and fractional crystallization. Minerals crystallize from magma in a sequential pattern known as Bowen’s reaction series.

Section 5.2 Study Guide Section 5.2 Main Ideas Igneous rocks are classified as felsic, mafic, intermediate, and ultramafic, depending upon their mineral compositions. Felsic rocks such as granite are light-colored, have high silica contents, and contain quartz and feldspars. Mafic rocks such as gabbro are dark-colored, have lower silica contents, and are rich in iron and magnesium. Intermediate rocks have moderate silica levels. Ultramafic rocks have low silica contents and very high levels of iron and magnesium. Igneous groups can be further identified by crystal size and texture. Early forming minerals may have well-shaped crystals, while later-forming minerals have irregular shapes. Porphyritic textures contain both large and small crystals.

Section 5.2 Study Guide Section 5.2 Main Ideas Igneous rocks such as granite are often used as building materials because of their strength, durability, and beauty. Valuable ore deposits and gems are often associated with igneous intrusions. Ores of rare elements such as lithium and beryllium are found in veins of extremely large-grained minerals called pegmatites. Diamonds are found in rare types of igneous intrusions known as kimberlites.

Chapter Assessment Multiple Choice 1. The process wherein different minerals form at different temperatures is called ____. a. partial melting b. Bowen’s reaction series c. fractional crystallization d. crystal separation Partial melting is when some minerals melt at low temperatures while others remain solid. Bowen’s reaction series describes in what order minerals form. Crystal separation is a hypothesis that answers questions about Bowen’s reaction series.

Chapter Assessment Multiple Choice 5. Extrusive igneous rocks generally have small mineral grains because ____. a. they cool slowly. b. the minerals in extrusive rocks do not form crystals under any condition. c. they cool quickly. d. there is too much water in the magma. By quickly cooling, the minerals in extrusive igneous rocks do not have enough time to form large crystals.

Chapter Assessment Short Answer 6. What characteristics make igneous rocks useful as building materials? Igneous rocks are useful as building materials because the interlocking grain textures of igneous rocks help to give them strength and many of the minerals found in igneous rocks are resistant to weathering.

Chapter Assessment Short Answer 7. What causes a porphyritic texture to form in certain rocks? A porphyritic texture indicates a complex cooling history wherein a slowly cooling magma suddenly began cooling rapidly.

Image Bank Chapter 5 Images

Image Bank Chapter 5 Images

Image Bank Chapter 5 Images