Presentation on theme: "Objectives Vocabulary Sequence the formation of sedimentary rocks."— Presentation transcript:
1Objectives Vocabulary Sequence the formation of sedimentary rocks. Explain the formation and classification of clastic sediments.Describe features of sedimentary rocks.Vocabularysedimentclasticdepositionlithificationcementationbeddinggraded beddingcross-bedding
2Formation of Sedimentary Rocks Much of Earth’s surface is covered with sediments.Sediments are pieces of solid material that have been deposited on Earth’s surface by wind, water, ice, gravity, or chemical precipitation.When sediments become cemented together, they form sedimentary rocks.The formation of sedimentary rocks begins when weathering and erosion produce sediments.
3Formation of Sedimentary Rocks WeatheringWherever Earth’s crust is exposed at the surface it is subject to weathering.Weathering is a set of physical and chemical processes that break rock into smaller pieces.Chemical weathering occurs when the minerals in a rock are dissolved or otherwise chemically changed.Minerals remain chemically unchanged during physical weathering.
5Formation of Sedimentary Rocks WeatheringClastic describes rock and mineral fragments produced by weathering and erosion.Clastic sediments range in size from huge boulders to microscopic particles.
6Formation of Sedimentary Rocks Erosion and TransportAfter rock fragments have been weathered out of outcrops, they are transported to new locations.Erosion is the removal and movement of surface materials from one location to another.The four main agents of erosion are wind, moving water, gravity, and glaciers.Eroded materials are almost always carried downhill.
7Erosion and Transport Deposition Formation of Sedimentary RocksErosion and TransportDepositionDeposition occurs when sediments are laid down on the ground or sink to the bottoms of bodies of water.Sediments are deposited when transport stops.As water or wind slows down, the largest particles settle out first, then the next-largest, and so on, so that different-sized particles are sorted into layers.Since wind can move only small grains, sand dunes are commonly made of fine, well-sorted sand.Sediment deposits from glaciers and landslides are not sorted because both move all materials with equal ease.
8Erosion and Transport Burial Formation of Sedimentary RocksErosion and TransportBurialMost sediments are ultimately deposited on Earth in depressions called sedimentary basins.These basins may contain layers of sediment that together are more than 8 km thick.As more and more sediment is deposited in an area, the bottom layers are subjected to increasing pressure and temperature which causes lithification.Lithification includes the physical and chemical processes that transform sediments into sedimentary rocks.
9Formation of Sedimentary Rocks LithificationLithification begins as the weight of overlying sediments forces the sediment grains closer together, causing the physical changes.Layers of mud shrink as excess water is squeezed out.
10Lithification Sand resists additional compaction during burial. Formation of Sedimentary RocksLithificationSand resists additional compaction during burial.Grain-to-grain contacts in sand form a supporting framework that helps maintain open spaces between the grains.
11Formation of Sedimentary Rocks LithificationThe temperature in Earth’s crust increases with depth by about 30°C per kilometer.Sediments that are buried 3 to 4 km deep experience temperatures that are high enough to start the chemical and mineral changes that cause cementation.Cementation occurs when mineral growth cements sediment grains together into solid rock.
12Lithification There are two common types of cementation. Formation of Sedimentary RocksLithificationThere are two common types of cementation.A new mineral, such as calcite (CaCO3) or iron oxide (Fe2O3) grows between sediment grains as dissolved minerals precipitate out of groundwater.Existing mineral grains grow larger as more of the same mineral precipitates from groundwater and crystallizes around them.
13Features of Sedimentary Rocks Formation of Sedimentary RocksFeatures of Sedimentary RocksBedding, or horizontal layering, is the primary feature of sedimentary rocks.The type of bedding depends upon the method of transport.The size of the grains and the material within the bedding depend upon many factors.
14Features of Sedimentary Rocks Formation of Sedimentary RocksFeatures of Sedimentary RocksGraded bedding is bedding in which the particle sizes become progressively heavier and coarser towards the bottom layers.Graded bedding is often observed in marine sedimentary rocks that were deposited by underwater landslides.
15Features of Sedimentary Rocks Formation of Sedimentary RocksFeatures of Sedimentary RocksCross-bedding is formed as inclined layers of sediment move forward across a horizontal surface.
16Features of Sedimentary Rocks Formation of Sedimentary RocksFeatures of Sedimentary RocksSmall-scale cross-bedding can be observed at sandy beaches and along sandbars in streams and rivers.Most large-scale cross-bedding is formed by migrating sand dunes.Small sedimentary features such as ripple marks are also preserved in sedimentary rocks.If a rippled surface is buried gently by more sediment without being disturbed, it might later be preserved in solid rock.
17Features of Sedimentary Rocks Formation of Sedimentary RocksFeatures of Sedimentary RocksEvidence of Past LifeFossils are probably the best-known features of sedimentary rocks.Fossils are the preserved remains, impressions, or any other evidence of once-living organisms.Fossils are of great interest to Earth scientists because fossils provide evidence of the types of organisms that lived in the distant past, the environments that existed in the past, and how organisms have changed over time.
18Formation of Sedimentary Rocks Section Assessment1. Match the following terms with their definitions.___ clastic___ deposition___ lithification___ beddingCDBAA. horizontal layering of sedimentary rocksB. the physical and chemical processes that transform sediments into sedimentary rocksC. rock and mineral fragments produced by weathering and erosionD. occurs when sediments are laid down on the ground or sink to the bottoms of bodies of water
19Section Assessment 2. How is cross-bedding formed? Formation of Sedimentary RocksSection Assessment2. How is cross-bedding formed?Cross-bedding is formed as inclined layers of sediment move forward across a horizontal surface.
20Formation of Sedimentary Rocks Section Assessment3. Identify whether the following statements are true or false.________ Cementation is a form of lithification.________ During deposition, the largest particles end up in the top layer.________ Graded bedding is often observed in marine sedimentary rocks.________ Clastic sediments can range in size from microscopic particles to huge boulders.truefalse
22Objectives Vocabulary Describe the types of clastic sedimentary rocks. Types of Sedimentary RocksObjectivesDescribe the types of clastic sedimentary rocks.Explain how chemical sedimentary rocks form.Describe organic sedimentary rocks.Recognize the importance of sedimentary rocks.Vocabularyclastic sedimentary rockporosityevaporite
23Types of Sedimentary Rocks The classification of sedimentary rocks is based on how they were formed.There are three main groups of sedimentary rocks: clastic, organic, and chemical.
25Clastic Sedimentary Rocks Types of Sedimentary RocksClastic Sedimentary RocksClastic sedimentary rocks, the most common type of sedimentary rocks, are formed from the abundant deposits of loose sediments found on Earth’s surface.Clastic sedimentary rocks are further classified according to the sizes of their particles.
26Clastic Sedimentary Rocks Types of Sedimentary RocksClastic Sedimentary RocksCourse-Grained ClasticsSedimentary rocks consisting of gravel-sized rock and mineral fragments are classified as coarse-grained clastics.Conglomerates are coarse-grained sedimentary rocks that have rounded particles, whereas breccias contain angular fragments.Conglomerates, such as gravel, are transported by high-energy flows of water and it becomes abraded and rounded as the particles scrape against one another.The angularity of particles in breccias indicates that the sediments did not have time to become rounded.
27Clastic Sedimentary Rocks Types of Sedimentary RocksClastic Sedimentary RocksMedium-Grained ClasticsSedimentary rocks that contain sand-sized rock and mineral fragments are classified as medium-grained clastic rocks.Sandstone is formed when these medium-sized sediments are buried and lithified.Sandstone has high porosity of up to 30 percent.Porosity is the percentage of open spaces between grains in a rock.Sandstone layers are valuable as underground reservoirs of oil, natural gas, and groundwater.
28Clastic Sedimentary Rocks Types of Sedimentary RocksClastic Sedimentary RocksFine-Grained ClasticsSedimentary rocks consisting of silt and mud are called siltstone and mudstone.Siltstone is mostly composed of silt-sized grains, while shale is composed mostly of silt and clay-sized particles.Shale has very low porosity and often forms barriers that hinder the movement of groundwater and oil.
29Chemical Sedimentary Rocks Types of Sedimentary RocksChemical Sedimentary RocksDuring chemical weathering, minerals can be dissolved and carried into lakes and oceans.As water evaporates from the lakes and oceans, the dissolved minerals are left behind.In arid regions, high evaporation rates can increase the concentration of dissolved minerals in bodies of water.
30Chemical Sedimentary Rocks Types of Sedimentary RocksChemical Sedimentary RocksRocks Formed from EvaporationWhen the concentration of dissolved minerals in a body of water reaches saturation, crystal grains precipitate out of solution and settle to the bottom.Evaporites are the layers of chemical sedimentary rocks that form as a result of the precipitation of crystal grains.Evaporites most commonly form in arid regions, in oceans and in drainage basins on continents that have low water flow.The three most common evaporite minerals are calcite (CaCO3), halite (NaCl), and gypsum (CaSO4).
31Chemical Sedimentary Rocks Types of Sedimentary RocksChemical Sedimentary RocksRocks Formed from Evaporation
32Chemical Sedimentary Rocks Types of Sedimentary RocksChemical Sedimentary RocksOrganic Sedimentary RocksOrganic sedimentary rocks are formed from the remains of once-living things.The most abundant organic sedimentary rock is limestone, which is composed primarily of calcite.Calcite comes from the calcium carbonate that some organisms use to make their shells.Calcium carbonate precipitates out of the water and crystallizes between the grains of carbonate sediment to form limestone.Limestone is common in shallow water environments.
33Chemical Sedimentary Rocks Types of Sedimentary RocksChemical Sedimentary RocksOrganic Sedimentary RocksAnother type of organic sedimentary rock, coal, forms from the remains of plant material.Over long periods of time, thick layers of vegetation slowly accumulate in swamps and coastal areas and are buried and compressed.Coal is composed almost entirely of carbon and can be burned for fuel.
34Importance of Sedimentary Rocks Types of Sedimentary RocksImportance of Sedimentary RocksThe characteristic textures and features of sedimentary rocks provide a geologic “snapshot” of surface conditions in Earth’s past.By considering all of this information, geologists can better understand how geologic changes occur over time.
35Importance of Sedimentary Rocks Types of Sedimentary RocksImportance of Sedimentary RocksEnergy ResourcesThe study of sedimentary rocks has great practical value because many of the natural resources used by humans come from sedimentary rocks.Oil, natural gas, coal, uranium, phosphate, and iron are found in sedimentary rocks.Limestone is processed to make cement for the construction industry.Sandstone and limestone are often cut into blocks for use in walls and buildings.
36Types of Sedimentary Rocks Section Assessment1. What is porosity and how is it a valuable characteristic?Porosity is the percentage of open spaces between grains in a rock. It is a valuable characteristic because a rock with high porosity, such as sandstone, can be an underground reservoir for oil, natural gas, and groundwater.
37Types of Sedimentary Rocks Section Assessment2. The following are which type of sedimentary rock?___ coal___ sandstone___ limestone___ shale___ conglomerate___ rock gypsum___ brecciaCAEBA. clasticB. chemicalC. organicD. A and BE. B and C
38Types of Sedimentary Rocks Section Assessment3. What are the three most common evaporite minerals?The three most common evaporite minerals are calcite (CaCO3), halite (NaCl), and gypsum (CaSO4).
40Metamorphic RocksObjectivesCompare and contrast the different types and causes of metamorphism.Distinguish among metamorphic textures.Explain how mineral and compositional changes occur during metamorphism.Understand how rocks continuously change from one type to another in the rock cycle.
42Causes of Metamorphism Metamorphic RocksCauses of MetamorphismMetamorphic rock forms when high temperature and pressure combine to alter the texture, mineralogy, or chemical composition of a rock without melting it.The high temperatures ultimately are derived from Earth’s internal heat.The high pressures can be generated in two ways:From vertical pressure caused by the weight of overlying rockFrom the compressive forces generated as rocks are deformed during mountain building
43Metamorphic RocksTypes of MetamorphismDifferent combinations of temperature and pressure result in different types of metamorphism.Large belts of regional metamorphism are produced when high temperature and pressure affect large regions of Earth’s crust.Regional metamorphism can be low grade, intermediate grade, and high grade.The grade of regional metamorphism reflects the relative intensity of temperature and pressure.
45Metamorphic RocksTypes of MetamorphismGeologists have divided the regional metamorphic belt that has been mapped in the northeastern United States belt into zones based upon the mineral groups found in the rocks.
46Metamorphic RocksTypes of MetamorphismKnowing the temperatures that certain areas experienced when rocks were forming can help geologists locate economically valuable metamorphic minerals.
47Metamorphic RocksTypes of MetamorphismSome key minerals are used to map metamorphic zones.
48Metamorphic RocksTypes of MetamorphismA local effect called contact metamorphism occurs when molten rocks, such as those in an igneous intrusion, come in contact with solid rock.High temperature and moderate-to-low pressure form the mineral assemblages that are characteristic of contact metamorphism.
49Metamorphic RocksTypes of MetamorphismBecause temperature decreases with distance from an intrusion, metamorphic effects also decrease with distance.Contact metamorphism from extrusive igneous rocks is limited to thin zones.
50Metamorphic RocksTypes of MetamorphismHydrothermal metamorphism occurs when very hot water reacts with rock and alters its chemistry and mineralogy.Hydrothermal fluids can dissolve some minerals, break down others, and deposit new minerals.Hydrothermal metamorphism is common around igneous intrusions and near active volcanoes.
51Metamorphic RocksMetamorphic TexturesMetamorphic rocks are classified into two textural groups: foliated and nonfoliated.Foliated metamorphic rocks are characterized by wavy layers and bands of minerals.High pressure during metamorphism causes minerals with flat or needlelike crystals to form with their long axes perpendicular to the pressure.
52Metamorphic RocksMetamorphic TexturesNonfoliated metamorphic rocks lack mineral grains with long axes in one direction.Nonfoliated rocks are composed mainly of minerals that form with blocky crystal shapes.Quartzite and marble are two common examples of nonfoliated rocks.
53Metamorphic Textures Porphyroblasts Metamorphic RocksMetamorphic TexturesPorphyroblastsUnder certain conditions, new metamorphic minerals can grow quite large while the surrounding minerals remain small.Porphyroblasts are large crystals, which can range in size from a few millimeters to a few centimeters.Porphyroblasts are found in areas of both contact and regional metamorphism.
54Metamorphic RocksMineral ChangesMinerals are stable at certain temperatures and crystallize from magma at different temperatures.During metamorphism, the minerals in a rock change into new minerals that are stable under the new temperature and pressure conditions.Minerals that change in this way are said to undergo solid-state alterations.
55Compositional Changes Metamorphic RocksCompositional ChangesWhen hot fluids migrate in and out of the rock during metamorphism the original composition of the rock can change.Chemical changes are especially common during contact metamorphism near igneous intrusions.Valuable ore deposits of gold, copper, zinc, tungsten, and lead are formed through the invasion of hydrothermal fluids.
56Metamorphic RocksThe Rock CycleMetamorphic rocks are formed by the changing of other rocks.Any rock can be changed into any other type of rock.The rock cycle is the continuous changing and remaking of rocks.
57Other Possible Paths There is more than one path in the rock cycle. Metamorphic RocksOther Possible PathsThere 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.
58Metamorphic RocksSection Assessment1. Match the following terms with their definitions.___ foliated___ nonfoliated___ porphyroblasts___ rock cycleCADBA. metamorphic rocks that lack grains with their long axes in one directionB. the continuous changing and remaking of rocksC. metamorphic rock with wavy layers and bands of mineralsD. large crystals in metamorphic rocks that are surrounded by smaller crystals
59Section Assessment 2. Identify what causes each type of metamorphism. Metamorphic RocksSection Assessment2. Identify what causes each type of metamorphism.___ regional___ contact___ hydrothermalBA. very hot water reacts with rock and alters its chemistry and mineralogyB. high temperatures and pressures affect large areas of Earth’s crustC. molten lava hardens on Earth’s surfaceD. molten rocks come in contact with solid rockDA
60Metamorphic RocksSection Assessment3. How can sedimentary rocks skip the metamorphic and igneous stages in the rock cycle?Rocks can take many different paths through the rock cycle. If a sedimentary rock is raised through uplifting and exposed to weathering and erosion it breaks into sediments, possibly to be reformed into new sedimentary rock.
62Chapter Resources Menu Study GuideSection 6.1Section 6.2Section 6.3Chapter AssessmentImage BankChapter Resources Menu
63Section 6.1 Study GuideSection 6.1 Main IdeasThe processes of weathering, erosion, deposition, burial, and lithification form sedimentary rocks.Clastic sediments are rock and mineral fragments produced by weathering and erosion. They are classified based on particle size.Sediments are lithified into rock by the processes of compaction and cementation.Sedimentary rocks can contain depositional features such as horizontal bedding, cross-bedding, and ripple marks.Fossils are the remains or other evidence of once-living things that are preserved in sedimentary rocks.
64Section 6.2 Study GuideSection 6.2 Main IdeasThere are three main classes of sedimentary rocks: clastic, which are formed from clastic sediments; chemical, which are formed from minerals precipitated from water; and organic, which are formed from the remains of once-living things.Clastic sedimentary rocks are classified by particle size and shape.Evaporites are chemical sedimentary rocks that form primarily in restricted ocean basins in regions with high evaporation rates.Limestone, composed primarily of calcite, is the most abundant organic sedimentary rock. Coal is another organic sedimentary rock.Sedimentary rocks provide geologists with information about surface conditions that existed in Earth’s past.
65Section 6.3 Study GuideSection 6.3 Main IdeasMetamorphic rocks are formed when existing rocks are subjected to high temperature and pressure, which cause changes in the rocks’ textures, mineralogy, and composition.The three main types of metamorphism are regional, contact, and hydrothermal.Metamorphic rocks are divided into two textural groups: foliated and nonfoliated.During metamorphism, minerals change into new minerals that are stable under the conditions of temperature and pressure at which they formed.The rock cycle is the set of processes whereby rocks continuously change into other types of rock.
66Chapter AssessmentMultiple Choice1. What is it called when sediments are laid down on the ground or sink to the bottoms of bodies of water?a. erosion c. depositionb. transport d. lithificationErosion is the removal of surface. Transport is the movement of eroded materials from one location to another. Lithification is the chemical and physical processes that transform sediments into sedimentary rocks.
67Chapter AssessmentMultiple Choice2. Oil and natural gas reserves will most likely be found in what type of rock?a. sandstone c. limestoneb. shale d. gypsumSandstone has a high porosity, or percentage of open spaces between the grains of the rock. Porosities of sandstone can be as high as 30 percent.
68Chapter AssessmentMultiple Choice3. What are the chemical sedimentary rocks that form as a result of crystal grains precipitating out of a solution called?a. porphyroblasts c. clasticb. evaporites d. sedimentsEvaporite refers to the evaporation that helps a solution (body of water) become supersaturated. When a solution is supersaturated, crystal grains can precipitate out and collect at the bottom where they become evaporite sedimentary rock.
69Chapter AssessmentMultiple Choice4. Which of the following is an example of a nonfoliated metamorphic rock?a. schist c. gneissb. slate d. quartziteUnlike foliated rocks, nonfoliated metamorphic rocks lack mineral grains with long axis in one direction. Schist, slate, and gneiss are all foliated rocks.
70Chapter AssessmentMultiple Choice5. What is the horizontal layering that is a primary characteristic in sedimentary rocks called?a. bedding c. metamorphismb. cementation d. ripple marksBedding can range from a millimeter thick layer of shale to sandstone deposits several meters thick. The type of bedding depends upon the method of transport.
71Chapter AssessmentShort Answer6. What are the three grades of regional metamorphism and how do they relate to temperature and pressure?The three grades of regional metamorphism are low grade, intermediate grade, and high grade. The grade of regional metamorphism reflects the relative intensity of temperature and pressure, with low grade metamorphism reflecting the lowest temperature and pressure.
72Chapter AssessmentShort Answer7. What is the geological significance of sedimentary rocks in relation to Earth’s past?The characteristics of textures and features in sedimentary rocks, such as cross-bedding, ripple marks, layering, and fossils, provide a geologic “snapshot” of surface conditions in Earth’s past.
73Chapter AssessmentTrue or False8. Identify whether the following statements are true or false.______ Contact metamorphism is a local effect.______ Clastic sediments are created through a metamorphic process.______ Cementation is part of the lithification process.______ Coal forms from the remains of plant material.______ Hydrothermal metamorphism does not alter the chemistry or mineralogy of a rock.truefalse
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