Prentice Hall EARTH SCIENCE Tarbuck Lutgens Chapter 3
Prentice Hall EARTH SCIENCE Tarbuck Lutgens
Chapter 3 Rocks
3. 1 The Rock Cycle KEY CONCEPTS • What is a rock? • What are three major types of rocks? • How do igneous, sedimentary, and metamorphic rocks differ? • What is the rock cycle? • What powers Earth’s rock cycle?
3. 1 The Rock Cycle Rocks are any solid mass of mineral or mineral-like matter occurring naturally as part of our planet.
3. 1 The Rock Cycle Rocks Types of Rocks 1. Igneous rock is formed by the crystallization of molten magma.
3. 1 The Rock Cycle Rocks Types of Rocks 2. Sedimentary rock is formed from the weathered products of preexisting rocks that have been transported, deposited, compacted, and cemented.
3. 1 The Rock Cycle Rocks Types of Rocks 3. Metamorphic rock is formed by the alteration of pre-existing rock deep within Earth (but still in the solid state) by heat, pressure, and/or chemically active fluids.
3. 1 The Rock Cycle Shows the interrelationships among the three rock types (igneous, sedimentary, and metamorphic)
The Rock Cycle
3. 1 The Rock Cycle Magma is molten material that forms deep beneath the Earth’s surface. Lava is magma that reaches the surface.
3. 1 The Rock Cycle Weathering is a process in which rocks are broken down by water, air, and living things. Sediment is weathered pieces of Earth elements.
The Rock Cycle
3. 1 The Rock Cycle Energy That Drives the Rock Cycle Processes driven by heat from the Earth’s interior are responsible forming both igneous rock and metamorphic rock. Weathering and the movement of weathered materials are external processes powered by energy from the sun. External processes produce sedimentary rocks.
3. 2 Igneous Rocks KEY CONCEPTS • How are intrusive and extrusive igneous rocks alike and different? • How does the rate of cooling affect an igneous rock’s texture? • How are igneous rocks classified according to composition?
3. 2 Igneous Rocks Formation of Igneous Rocks 1. Intrusive igneous rocks are formed when magma hardens beneath Earth’s surface. 2. Extrusive igneous rocks are formed when lava hardens.
3. 2 Igneous Rocks Classification of Igneous Rocks Igneous rocks can be classified based on their composition and texture. 1. Texture • Coarse-grained texture. • Fine-grained texture
Course-Grained Igneous Texture • Coarse-grained texture is caused by slow cooling resulting in larger crystals.
Fine-Grained Igneous Texture • Fine-grained texture is caused by rapid cooling resulting in smaller, interconnected mineral grains.
3. 2 Igneous Rocks Classification of Igneous Rocks 1. Texture (continued) • Glassy texture. • Porphyritic texture.
Obsidian Exhibits a Glassy Texture. • Glassy texture is caused by very rapid cooling. • When the magma contains a small amount of dissolved gases, a glassy texture will result.
Porphyritic Igneous Texture • Porphyritic texture is caused by different rates of cooling resulting in varied sized minerals.
3. 2 Igneous Rocks Classification of Igneous Rocks 2. Composition • Granitic composition rocks are made mostly of light-colored quartz and feldspar.
3. 2 Igneous Rocks Classification of Igneous Rocks 2. Composition (continued) • Basaltic composition rocks are made mostly of dark-colored silicate minerals and plagioclase feldspar.
3. 2 Igneous Rocks Classification of Igneous Rocks 2. Composition (continued) • Andesitic composition rocks are between granitic light-color minerals and basaltic composition darkcolored minerals.
3. 2 Igneous Rocks Classification of Igneous Rocks 2. Composition (continued) • Ultramafic composition rocks are made mostly from iron and magnesium-rich minerals.
Classification of Igneous Rocks
3. 3 Sedimentary Rocks KEY CONCEPTS • Describe the major process involved in the formation of sedimentary rocks. • What are clastic sedimentary rocks? • What are chemical sedimentary rocks? • What features are unique to some sedimentary rocks?
3. 3 Sedimentary Rocks Formation of Sedimentary Rocks Weathering, Erosion, and Deposition • Erosion involves the weathering and the removal of rock. • Deposition occurs when an agent of erosion—water, wind, ice, or gravity—loses energy and drops sediments.
3. 3 Sedimentary Rocks Formation of Sedimentary Rocks Compaction and Cementation • Compaction is a process that squeezes, or compacts, sediments. • Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments.
3. 3 Sedimentary Rocks Classification of Sedimentary Rocks Two Main Groups 1. Clastic sedimentary rocks are composed of weathered bits of rocks and minerals. • Classified by particle size
3. 3 Sedimentary Rocks Classification of Sedimentary Rocks Two Main Groups 1. Clastic sedimentary rocks: • Common rocks include - Shale - Conglomerate - Sandstone
Shale with Plant Fossils
Conglomerate
3. 3 Sedimentary Rocks Classification of Sedimentary Rocks Two Main Groups 2. Chemical sedimentary rocks form when dissolved substances precipitate, or separate, from water.
3. 3 Sedimentary Rocks Classification of Sedimentary Rocks Two Main Groups 2. Chemical sedimentary rocks: • Common rocks include - Limestone — - microcrystalline quartz most abundant known as chert, flint, jasper, chemical rock or agate
3. 3 Sedimentary Rocks Classification of Sedimentary Rocks Two Main Groups 2. Chemical sedimentary rocks: • Common rocks include - evaporites such - coal as rock salt or gypsum
3. 3 Sedimentary Rocks Classification of Sedimentary Rocks 1. organic sedimentary rock that forms from the remains of plants or animals 2. Coal and some limestones are examples of organic rocks
3. 3 Sedimentary Rocks Fossils and Concretions • Fossils are the remains of organisms that are preserved in rock. • Concretions are lumps of minerals that precipitate from fluids and build up around a nucleus or in a cavity in existing rock
Fossiliferous Limestone
Classification of Sedimentary Rocks
3. 3 Sedimentary Rocks Features of Some Sedimentary Rocks Features of sedimentary rocks are clues to how and where the rocks are formed (i. e. organic sedimentary rock)
3. 4 Metamorphic Rocks KEY CONCEPTS • Where does most metamorphism take place? • How is contact metamorphism differ from regional metamorphism? • What are three agents of metamorphism, and what kinds of changes does each cause? • What are foliated metamorphic rocks, and how do they form? • How are metamorphic rocks classified?
3. 4 Metamorphic Rocks Formation of Metamorphic Rocks Metamorphism means “to change form. ” Most metamorphic changes occur at elevated temperatures and pressures.
3. 4 Metamorphic Rocks Formation of Metamorphic Rocks Conditions formation are found a few kilometers below the Earth’s surface and extend into the upper mantle.
3. 4 Metamorphic Rocks Formation of Metamorphic Rocks Contact metamorphism occurs when magma moves into rock. • Occurs near a body of magma • Changes are driven by a rise in temperature.
3. 4 Metamorphic Rocks Formation of Metamorphic Rocks Regional metamorphism results in largescale deformation and high-grade metamorphism. • Directed pressures and high temperatures occur during mountain building. • Produces the greatest volume of metamorphic rock
Origin of Pressure in Metamorphism
3. 4 Metamorphic Rocks Agents of Metamorphism Heat • Provides the energy needed to drive chemical reactions Pressure • Causes a more compact rock with greater density
Origin of Pressure in Metamorphism
3. 4 Metamorphic Rocks Agents of Metamorphism Hydrothermal Solutions • Hot water-based solutions escaping from the mass of magma • Promote recrystallization by dissolving original minerals and then depositing new ones
3. 4 Metamorphic Rocks Classification of Metamorphic Rocks Two main categories 1. Foliated Metamorphic Rock • Has a banded or layered appearance • Extreme pressure may cause the mineral crystals in the rock to realign or re-grow to form parallel bands
3. 4 Metamorphic Rocks Classification of Metamorphic Rocks Two main categories 1. Foliated Metamorphic Rock • Foliated metamorphic rocks include the common rocks; slate, schist, and gneiss
3. 4 Metamorphic Rocks Classification of Metamorphic Rocks Two main categories 2. Nonfoliated Metamorphic Rock • Does not have a banded texture • Many nonfoliated metamorphic rocks contain grains of only one mineral or contain very small amounts of other minerals
3. 4 Metamorphic Rocks Classification of Metamorphic Rocks Two main categories 2. Nonfoliated Metamorphic Rock • Nonfoliated metamorphic rocks include the common rocks marble and quartzite
Classification of Metamorphic Rocks
Gneiss Typically Displays a Banded Appearance
Marble—A Nonfoliated Metamorphic Rock
Chapter 3 Rocks
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