Presentation is loading. Please wait.

Presentation is loading. Please wait.

Rocks: IgneousIgneous SedimentarySedimentary MetamorphicMetamorphic Keepers of Earth’s History 1.

Similar presentations


Presentation on theme: "Rocks: IgneousIgneous SedimentarySedimentary MetamorphicMetamorphic Keepers of Earth’s History 1."— Presentation transcript:

1 Rocks: IgneousIgneous SedimentarySedimentary MetamorphicMetamorphic Keepers of Earth’s History 1

2 What’s in your rock?: Hornblende Orthoclase Quartz aggregates of minerals Granite Biological material Fossil fragments Plant material 3

3 Understanding rocks is the basic foundation of knowledge for earth scientists and materials that make up the earth. Understanding rocks is the basic foundation of knowledge for earth scientists and materials that make up the earth. Every rock “speaks” to the observer and gives Every rock “speaks” to the observer and gives clues about where and how it was formed. clues about where and how it was formed. Rocks are divided into 3 major groups: Rocks are divided into 3 major groups: Igneous Igneous formed from solidifying hot molten formed from solidifying hot molten rock (magma) rock (magma) Every rock “speaks” to the observer and gives Every rock “speaks” to the observer and gives clues about where and how it was formed. clues about where and how it was formed. Rocks are divided into 3 major groups: Rocks are divided into 3 major groups: Igneous Igneous formed from solidifying hot molten formed from solidifying hot molten rock (magma) rock (magma) Sedimentary Sedimentary formed on the surface of the earth from formed on the surface of the earth from weathering processes weathering processes Sedimentary Sedimentary formed on the surface of the earth from formed on the surface of the earth from weathering processes weathering processes Metamorphic Metamorphic pre-existing rocks are subjected to pre-existing rocks are subjected to various pressure and temperature various pressure and temperature relationships relationships Metamorphic Metamorphic pre-existing rocks are subjected to pre-existing rocks are subjected to various pressure and temperature various pressure and temperature relationships relationships 4

4 How does an earth scientist distinguish between the three rock types (Ig, Seed, and Met)? Texture: the appearance of the rock the appearance of the rock size, shape, and arrangement of mineral grains. size, shape, and arrangement of mineral grains. Composition (mineral assemblages) types and relative proportions of minerals types and relative proportions of minerals making up a rock making up a rock composition, mineral make-up, chemistry--all composition, mineral make-up, chemistry--all indicators of a rock’s composition indicators of a rock’s composition All rocks are identified based on their texture and composition. 5

5 The Rock Cycle The Sedimentary Cycle 6

6 The Rock Cycle: where the earth’s internal forces meet where the earth’s internal forces meet the earth’s external forces (at the earth’s the earth’s external forces (at the earth’s surface) surface) Earth’s internal forces Earth’s external forces moving continents (PT) moving continents (PT) earthquakes earthquakes elevation of mountains elevation of mountains volcanic eruptions volcanic eruptions the hydrosphere (HC) the hydrosphere (HC) atmosphere atmosphere erosion (wind, water, ice) erosion (wind, water, ice) biosphere activities biosphere activities Produce a continuous cycle of rising mountains only to be weathered down and uplifted repeatedly. As a result, igneous sedimentary, and metamorphic rocks are created. 7

7 II Earth Science, especially the rock cycle !!!!!!!!!!!!! Earth Science, especially the rock cycle !!!!!!!!!!!!! I will get an A on my exams and quizzes. Discuss with a friend: 1.Briefly identify each rock group and its geologic environment. its geologic environment. 2. Draw the rock cycle, and explain how the rock cycle works to your neighbor. rock cycle works to your neighbor. 3. Why is the rock cycle a “cycle”??? 8

8 Geology – Chapter 3 – Igneous Rocks Igneous Rocks 9

9 MagmaMagma Extrusive - igneous rocks – above the earth’s surface volcanic rocks volcanic rocks lava flows lava flows Example – Hawaiian Volcanoes Example – Hawaiian Volcanoes Intrusive - igneous rocks – below the earth’s surface plutonic rocks large granite mountains Example – Sierra Nevada Mountain Range the parent material for igneous rocks (if not all rock groups) the parent material for igneous rocks (if not all rock groups) typical temperature 1,200 o C (2,200 o F) typical temperature 1,200 o C (2,200 o F) forms about 250 km or 150 miles below the earth’s surface forms about 250 km or 150 miles below the earth’s surface Grain size determines if the ig rock is extrusive or intrusive. Magma determines the rock’s composition. 10

10 When observing “frozen magma” (an igneous rock), how does a geologist know if the rock is an Extrusive or Intrusive igneous rock? When observing “frozen magma” (an igneous rock), how does a geologist know if the rock is an Extrusive or Intrusive igneous rock? checking the crystal size - Does the rock contain visible crystals, or are crystals non-existent? checking the crystal size - Does the rock contain visible crystals, or are crystals non-existent? Factors that affect crystal size in an igneous rock: The rate at which magma cools slow cooling – visible mineralsslow cooling – visible minerals rapid cooling – non-visible mineralsrapid cooling – non-visible minerals Factors that affect crystal size in an igneous rock: The rate at which magma cools slow cooling – visible mineralsslow cooling – visible minerals rapid cooling – non-visible mineralsrapid cooling – non-visible minerals Igneous Rock Textures non-visible minerals rapid cooling magma rapid cooling magma extrusive ig rock extrusive ig rock non-visible minerals rapid cooling magma rapid cooling magma extrusive ig rock extrusive ig rock visible minerals slow cooling magma slow cooling magma intrusive ig rock intrusive ig rock visible minerals slow cooling magma slow cooling magma intrusive ig rock intrusive ig rock Cooled above the surface (fine-grained) Cooled above the surface (fine-grained) Cooled below the surface (coarse-grained) Cooled below the surface (coarse-grained) 11

11 Composition of Igneous Rocks How much silica (SiO 2 ) is in your igneous rock? Felsic compositions (feldspar + silica) light-colored igneous rocks light-colored igneous rocks common minerals: feldspar and quartz common minerals: feldspar and quartz 70% SiO 2 70% SiO 2 Mafic compositions (magnesium + iron) dark-colored igneous rocks dark-colored igneous rocks common minerals: olivine and pyroxene common minerals: olivine and pyroxene 50% SiO 2 50% SiO 2 ultramafic: composed entirely of olivine and pyroxene ultramafic: composed entirely of olivine and pyroxene and less than 50% silica (SiO 2 ) and less than 50% silica (SiO 2 ) Intermediate compositions: mixture of felsic and mafic minerals mixture of felsic and mafic minerals about 60% silica (SiO 2 ) about 60% silica (SiO 2 ) 14

12 How are igneous rocks classified? Using their TEXTURE and COMPOSITION Using their TEXTURE and COMPOSITION Igneous rocks are classified based on TEXTURE and COMPOSITION. TEXTURE COARSEphaneritic FINEaphanitic COMPOSITION Felsic (light color) 70% silica Mafic (dark color) 50% silica Intermediate color 60% silica GraniteDioriteGabbro RhyoliteAndesiteBasalt Igneous rocks have the same chemistry but different textural characteristics due to the type of geologic environment (cools quickly or slowly).

13 II Earth Science, especially igneous rocks. Earth Science, especially igneous rocks. I will get an A on my exams and quizzes. 1.What is the difference between extrusive and intrusive igneous rocks? and intrusive igneous rocks? 2. How can one tell the difference between an extrusive and intrusive rock texture? an extrusive and intrusive rock texture? 3. The composition of a mafic ig rock is…. The composition of a felsic ig rock is …. The composition of a felsic ig rock is …. 4. A fine-grained, light-colored ig rock is called a …………………. called a …………………. 17

14 Sedimentary Rocks 18

15 How is a sedimentary rock formed??? Pre-existingRockPre-existingRock erosionerosion water, wind, ice ice breaks down pre-existing rock breaks down pre-existing rock sedimentsediment transportedtransported LakesLakes RiversRivers DepositedDeposited compactedcementedcompactedcemented lithifiedlithifiedSedimentaryRockSedimentaryRock Why is the earth’s surface 75% sedimentary rocks? 19

16 Erosional processes – later (Chapter 4) Sediments are separated into 3 broad categories: Clastic sediments: Clastic sediments: inorganic grains or mineral fragments ranging in inorganic grains or mineral fragments ranging in size from boulders to clay particles (flour size) size from boulders to clay particles (flour size) Chemical sediment: formed by the precipitation of minerals dissolved formed by the precipitation of minerals dissolved in lakes, rivers, or seawater environments in lakes, rivers, or seawater environments Biogenic (bioclastic) sediment: Biogenic (bioclastic) sediment: sediment composed of animal and plant remains or sediment composed of animal and plant remains or material precipitated by biological processes material precipitated by biological processes Sediments are separated into 3 broad categories: Clastic sediments: Clastic sediments: inorganic grains or mineral fragments ranging in inorganic grains or mineral fragments ranging in size from boulders to clay particles (flour size) size from boulders to clay particles (flour size) Chemical sediment: formed by the precipitation of minerals dissolved formed by the precipitation of minerals dissolved in lakes, rivers, or seawater environments in lakes, rivers, or seawater environments Biogenic (bioclastic) sediment: Biogenic (bioclastic) sediment: sediment composed of animal and plant remains or sediment composed of animal and plant remains or material precipitated by biological processes material precipitated by biological processes To be a sedimentary rock, it must be lithified. 21

17 Lithification: processes by which sediment is transformed into sedimentary rock Lithification: processes by which sediment is transformed into sedimentary rock Sediment can be lithified in three common processes: Compaction: Overlying weight of the sediment “squeezes” and compresses pore spaces, which pushes particles together. Compaction: Overlying weight of the sediment “squeezes” and compresses pore spaces, which pushes particles together. A B A. loose, unconsolidated sediment with abundant pore space abundant pore space B. compacted, compressed sediment with reduced pore space reduced pore space A. loose, unconsolidated sediment with abundant pore space abundant pore space B. compacted, compressed sediment with reduced pore space reduced pore space Cementation: Pore water is expelled from voids, and rising water carries iron, calcium carbonate, and silica which precipitates as geological glue (cement) holding the grains together. Cementation: Pore water is expelled from voids, and rising water carries iron, calcium carbonate, and silica which precipitates as geological glue (cement) holding the grains together. Grains are cemented together by three Grains are cemented together by three types of cements: types of cements: iron cementiron cement calcium carbonate cementcalcium carbonate cement silica cementsilica cement Grains are cemented together by three Grains are cemented together by three types of cements: types of cements: iron cementiron cement calcium carbonate cementcalcium carbonate cement silica cementsilica cement 22

18 Lithification processes Recrystallization: Overlying pressure causes less stable minerals to convert to more stable minerals, producing new substances that cement pre-existing grains. Recrystallization: Overlying pressure causes less stable minerals to convert to more stable minerals, producing new substances that cement pre-existing grains. Overlying pressure Grain boundaries convert to more stable mineral compositions, “cementing” grains together. Grain boundaries convert to more stable mineral compositions, “cementing” grains together. 23

19 Clastic Sediment: lithifiedlithified gravel sediment ranging from pea-sized to larger gravel sediment ranging from pea-sized to larger conglomerateconglomerate sand-sized particles (fine to coarse sandpaper) sandpaper) sandstonesandstone finer particles – size of table salt siltstonesiltstone finest sedimentary particles (flour-size) finest sedimentary particles (flour-size) shaleshale lithifiedlithified lithifiedlithified lithifiedlithified 24

20 Chemical Sediments and Sedimentary Rocks Chemical Sediment: sediment formed by the precipitation of minerals dissolved in a lake, river, or seawater Chemical Sediment: sediment formed by the precipitation of minerals dissolved in a lake, river, or seawater All surface water and groundwater contain dissolved ions (chemicals), creating a venue for precipitation of chemical sediment. All surface water and groundwater contain dissolved ions (chemicals), creating a venue for precipitation of chemical sediment. Precipitation of chemical rocks takes place in two ways: Plants and animals alter the chemical balance Plants and animals alter the chemical balance of the water body (lake, ocean). of the water body (lake, ocean). Increasing amounts of calcium carbonate cause precipitation of limestone. cause precipitation of limestone. evaporation of chemically saturated water evaporation of chemically saturated water bodies bodies Precipitation of chemical rocks takes place in two ways: Plants and animals alter the chemical balance Plants and animals alter the chemical balance of the water body (lake, ocean). of the water body (lake, ocean). Increasing amounts of calcium carbonate cause precipitation of limestone. cause precipitation of limestone. evaporation of chemically saturated water evaporation of chemically saturated water bodies bodies 26

21 Evaporation of chemically saturated water creates a chemical sedimentary rock (evaporite). Na + Cl - a lake containing sodium (Na + ) and chlorine (Cl - )--free ions a lake containing sodium (Na + ) and chlorine (Cl - )--free ions EvaporationEvaporation NaCl Lake water is evaporated, concentrating sodium and chloride ions (saturation). Sodium and chlorine combine to form halite (table salt). Lake water is evaporated, concentrating sodium and chloride ions (saturation). Sodium and chlorine combine to form halite (table salt). 27

22 The Great Salt Lake, Utah (evaporite halite) The Great Salt Lake, Utah (evaporite halite) UtahUtah As lake becomes saturated, density of water increases. As lake becomes saturated, density of water increases. 28

23 Chemical – sedimentary rocks that have been precipitated or are the result of evaporation Chemical – sedimentary rocks that have been precipitated or are the result of evaporation Gypsum – evaporite CaSO 4 Halite – evaporite NaCl NaCl Limestone--precipitated calcium carbonate Limestone--precipitated 29

24 Biogenic Sediments and Biogenic Rocks: Biogenic sediment is composed of organic remains of plants and animals (bioclastic rocks). shell, bones, teeth, plant fragments, wood, roots shell, bones, teeth, plant fragments, wood, roots Biogenic Sediments and Biogenic Rocks: Biogenic sediment is composed of organic remains of plants and animals (bioclastic rocks). shell, bones, teeth, plant fragments, wood, roots shell, bones, teeth, plant fragments, wood, roots Common Biogenic Rocks: Limestone Limestone most abundant biogenic sedimentary rock most abundant biogenic sedimentary rock composed of calcium carbonate CaCO 3 (calcite, dolostone, composed of calcium carbonate CaCO 3 (calcite, dolostone, aragonite) aragonite) lithified shells, skeletal material lithified shells, skeletal material Common Biogenic Rocks: Limestone Limestone most abundant biogenic sedimentary rock most abundant biogenic sedimentary rock composed of calcium carbonate CaCO 3 (calcite, dolostone, composed of calcium carbonate CaCO 3 (calcite, dolostone, aragonite) aragonite) lithified shells, skeletal material lithified shells, skeletal material Chert Chert composed of silica SiO 2 composed of silica SiO 2 precipitated silica shells (made by sea animals) that protect microscopic sea animals – Animals die, and silica shells microscopic sea animals – Animals die, and silica shells sink, creating layers of chert beds on the ocean floor. sink, creating layers of chert beds on the ocean floor. Chert Chert composed of silica SiO 2 composed of silica SiO 2 precipitated silica shells (made by sea animals) that protect microscopic sea animals – Animals die, and silica shells microscopic sea animals – Animals die, and silica shells sink, creating layers of chert beds on the ocean floor. sink, creating layers of chert beds on the ocean floor. 30 “ When the animal dies, it loses the chert off its back.”

25 Common Biogenic Rocks Peat to Coal accumulated remains of terrestrial plants accumulated remains of terrestrial plants with time and pressure ---- peat with time and pressure ---- peat continued pressure and lithification coal continued pressure and lithification coal Peat to Coal accumulated remains of terrestrial plants accumulated remains of terrestrial plants with time and pressure ---- peat with time and pressure ---- peat continued pressure and lithification coal continued pressure and lithification coal PeatPeat Bituminous coal Anthracite coal Increasing pressure metamorphismmetamorphism lithificationlithification 31

26 Biogenic (bio-clastic) rocks – result from animal and plant secretions -- The term “clastic” indicates that these rocks contain fossils or parts of plants, shells, compacted plant material Biogenic (bio-clastic) rocks – result from animal and plant secretions -- The term “clastic” indicates that these rocks contain fossils or parts of plants, shells, compacted plant material Animal parts Cemented shell fragments CoquinaCoquina Fossil Limestone Chalk Microscopic fossils 32

27 What do sedimentary rocks tell the earth scientist? scientist? These rock “layers” were deposited one layer at a time and lithified. The banded appearance is known as bedding or groups of layers called strata. The boundary between each stratum is called a bedding surface. These rock “layers” were deposited one layer at a time and lithified. The banded appearance is known as bedding or groups of layers called strata. The boundary between each stratum is called a bedding surface. stratastrata beddingbedding Bedding surface By observing the sedimentary rock type (clastic, chemical, biogenic) and depositional patterns, an earth scientist can decipher the geologic history – like reading pages in a book. By observing the sedimentary rock type (clastic, chemical, biogenic) and depositional patterns, an earth scientist can decipher the geologic history – like reading pages in a book. 33

28 Sedimentary Rock Classification Summary Tree Sedimentary Rocks are divided into 3-classification categories: Clastic sediments Chemical sediments Bio-clastic (chemical) sediments composed of inorganic grains formed by precipitation plants and animalsevaporationprocesses composed of “animal parts” from classification based on distribution of grain sizes Conglomerate Sandstone Shale Siltstone Decreasing grain size Classification based on lack of grains and chemical composition Gypsum (CaSO 4 ) Halite (NaCl) Limestone (CaCO 3 ) Classification based on Observed fossils, animal parts, Plant/animal secretions Fossil-limestone Coquina Chalk

29 II sedimentary rock classification. I will get an A on my exams and quizzes. Discuss with a friend: 1.Describe at least 2 characteristics of each sedimentary rock classification each sedimentary rock classification (clastic, biogenic, chemical). (clastic, biogenic, chemical). 2.Give a rock example for each classification. 36

30 37

31 What is “metamorphism?” transformation of pre-existing rock to a metamorphic rock rock to a metamorphic rock through pressure and through pressure and temperature relationships temperature relationships transformation of pre-existing rock to a metamorphic rock rock to a metamorphic rock through pressure and through pressure and temperature relationships temperature relationships meta (change) morphism (form) All changes take place through All changes take place through solid state transformation. solid state transformation. All changes take place through All changes take place through solid state transformation. solid state transformation. 38

32 Types of Metamorphism (Temperature) takes place around 150 o C (Temperature) typically at depths of 5 km below the (Pressure) earth’s surface (Pressure) Types of Metamorphism (Temperature) takes place around 150 o C (Temperature) typically at depths of 5 km below the (Pressure) earth’s surface (Pressure) At this temperature and pressure, new minerals are formed – changed from one mineral to another. At this temperature and pressure, new minerals are formed – changed from one mineral to another. 39

33 II metamorphic rocks. I will get an A on my exams and quizzes. Discuss with a friend: 1.How do you define metamorphism? – Be specific. specific. 2.What two major factors are necessary for pre-existing rocks to become for pre-existing rocks to become metamorphosed? metamorphosed? 3. Where does metamorphism typically take place within the earth? take place within the earth? 40

34 2 Common types of metamorphism contact metamorphism regional metamorphism regional metamorphism 44

35 What is contact metamorphism? Contact metamorphism: Contact metamorphism: magma “contacts” solid rock – heat is transferred into overlying heat is transferred into overlying rocks through conduction – changing the pre-existing rock it intruded the pre-existing rock it intruded high heat/low pressure high heat/low pressure localized metamorphism localized metamorphism “fast-acting,” like touching a “fast-acting,” like touching a hot frying pan hot frying pan Contact metamorphism: Contact metamorphism: magma “contacts” solid rock – heat is transferred into overlying heat is transferred into overlying rocks through conduction – changing the pre-existing rock it intruded the pre-existing rock it intruded high heat/low pressure high heat/low pressure localized metamorphism localized metamorphism “fast-acting,” like touching a “fast-acting,” like touching a hot frying pan hot frying pan 45

36 Country rock (surrounding) is baked from conduction. 46

37 What is regional metamorphism? Regional Metamorphism Pre-existing rock is subjected to intense stresses and strains (deformation) usually from the forces of mountain building. high heat/high pressure high heat/high pressure very widespread geographically very widespread geographically like experiencing a slow sunburn like experiencing a slow sunburn Regional Metamorphism Pre-existing rock is subjected to intense stresses and strains (deformation) usually from the forces of mountain building. high heat/high pressure high heat/high pressure very widespread geographically very widespread geographically like experiencing a slow sunburn like experiencing a slow sunburn 47

38 Mountain building widespread belts 48

39 II the different ways to create Metamorphism. Metamorphism. I will get an A on my exams and quizzes. Discuss with a friend: Describe the conditions necessary for each type of metamorphism: contact metamorphismcontact metamorphism regional metamorphismregional metamorphism 49

40 Heat sources: contact with hot magma – heat penetrates overlying rocks (conduction) overlying rocks (conduction) geothermal gradient – heat increases with depth – rocks are hotter when buried depth – rocks are hotter when buried Heat sources: contact with hot magma – heat penetrates overlying rocks (conduction) overlying rocks (conduction) geothermal gradient – heat increases with depth – rocks are hotter when buried depth – rocks are hotter when buried 50 Metamorphic heat sources:

41 Geothermal Gradient Temperature increases Temperature increases as depth increases. as depth increases. Large thermal gradient Large thermal gradient is at the surface. is at the surface. Gradient decreases Gradient decreases after 1000 km depth. after 1000 km depth. Geothermal Gradient Temperature increases Temperature increases as depth increases. as depth increases. Large thermal gradient Large thermal gradient is at the surface. is at the surface. Gradient decreases Gradient decreases after 1000 km depth. after 1000 km depth Steep gradient 51

42 Pressure – increases with depth, various types of pressure rearrange minerals – minerals compact or elongate Pressure – increases with depth, various types of pressure rearrange minerals – minerals compact or elongate Confining pressure Differential pressure 52 Pressure associated with metamorphism

43 How does one know how much metamorphism has taken place in a rock? reflected in the rock’s texture reflected in the rock’s texture How does one know how much metamorphism has taken place in a rock? reflected in the rock’s texture reflected in the rock’s texture Not Metamorphosed Metamorphosed – mineral grains are in a preferred direction -- FOLIATION Metamorphosed – mineral grains are in a preferred direction -- FOLIATION 53

44 II to metamorphose. I will get an A on my exams and quizzes. Discuss with a friend: 1.Describe two heat sources associated with metamorphism. metamorphism. 2.Define the differences between confining and differential pressures. and differential pressures. 3. Draw a diagram that shows mineral orientation due to confining and orientation due to confining and differential type pressures. differential type pressures. 54


Download ppt "Rocks: IgneousIgneous SedimentarySedimentary MetamorphicMetamorphic Keepers of Earth’s History 1."

Similar presentations


Ads by Google