GEO 101-007 Final Exam Study Guide
GEO 101-007 Final Exam Study Guide GEO 101-007
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This page Study Guide was uploaded by Jennifer Gintovt on Sunday December 6, 2015. The Study Guide belongs to GEO 101-007 at University of Alabama - Tuscaloosa taught by Dr. William Lambert in Summer 2015. Since its upload, it has received 245 views. For similar materials see The Dynamic Earth in Geology at University of Alabama - Tuscaloosa.
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GEO 101007 Final Exam Study Guide What is geology The study of the earth 0 Rocks sediments rivers oceans the atmosphere plants animals and how they interact with one another today and in the past What is science Science is the human effort to understand or to better understand the natural world and how it works by observing physical evidence Science is done through observation The Kola Superdeep Borehole Russia Started drilling in 1970 Reached a maximum depth of 76 miles in 1989 Earths center is 6371 km Kola went 122 km which is O2 It is unlikely that the Kola Superdeep Borehole would ever reach the mantle due to the amount of Earth that was being drilled through 0 Drilling through oceanic crust as opposed to continental crust would have resulted in better results Continental vs Oceanic Crust Continental crust is much thicker than most oceanic crust Moho the boundary between the Earth s crust and mantle Scienti c method Recognizing the problem Collecting data Proposing hypothesis Testing hypothesis Theory 0 Scientific ideas explanations supported by an abundance of evidence they have passed many tests and have failed none Scientific law 0 Ideas that must be considered true based on everything we know of the natural Universe eg Newton s Law of Gravitation Geocentric Model without moving while the Moon and the planets whirled around it within a globe of stars Heliocentric Model 0 while the earth and other planets orbited around it The Milky Way 100000 light years across 0 1 light year 6 trillion miles The Do ler Effect Movement of the source of sound waves causes wave frequencywavelength to change thus changing the sound we hear Movement of the source of lightwaves causes wave frequencywavelength to change thus changing the color we see Applying the Doppler Effect to the Universe NASA took pictures of multiple galaxies The red color of the galaxies indicated that things are moving away from us meaning the universe is expanding If everything is expanding was all of it once together The Big Bang Theory Key Points The universe has a beginning The universe started infinitely small hot Early universe what mainly hydrogen and helium The universe is old I 137 billion years old 0 Most but not all scientists agree on this basic model 0000 How were most elements created 0 Nebular theory can help explain this answer as well Early Universe Composition Nebula formed as the universe cooled Hydrogen 74 Helium 24 Nebular Theory Gravitation between materials in nebula puled mass inward When pulled inward spin increased in accord with the conservation of angular momentum think figure skater The spinning cloud conformed to the shape of a spinning disk The center of the disk is the protosun Away from the center planetesimals formed Planetesimals accreted more matter to become planets Earth s Interior Lithosphere all of crust plus upper mantle rigid Asthenosphere portion of mantle that can ow not liquid Thickness of lithosphere varies boundary is where temperature is 1280 degrees C rock becomes soft enough to ow Moon Formation Theory Moon a sizeable body locked in orbit around a planet Small planet collides with Earth and produces a ring of debris around Earth that eventually becomes the moon Earth s magnetic Field Basically a dipole has a north and a south Produced by Earth s geodynamo o Melted iron moves within the outer core Magnetic field is constantly changing Magnetic field protects us from most but not all solar wind cosmic rays Earth s Thin Atmosphere 78 Nitrogen 21 Oxygen Other 1 argon carbon dioxide neon methane ozone carbon monoxide sulfur dioxide What is a mineral A solid natural not manmade substance in which atoms are arranged in an orderly pattern Igneous Rock Silica Content Felsic Intermediate Ma c Ultrama c Glass What IS 1t and Why IS It not a mineral A solid in which Silica content cooled rapidly Iron and ma 9 esium content Silica Silicate minerals silica mixed with varying proportions of other elements iron and magnesium Darker color Silicate rocks composed of silicate minerals Most common minerals on earth The Earth s Core Temp may exceed 4700 degrees C Pressure may exceed 3600000 atm Geothermal gradient The rate of change increase in temperature with depth 0 Upper crust 15 to 50 degrees C per Kilometer 0 At greater depths 10 degrees C per Kilometer Crust Outer shell different chemistry than mantle 0 Continental crust relatively thick felsic granite relatively low density 0 Oceanic crust relatively thin mafic basalt gabbro relatively high density Mantle 2885 km thick largest part of Earth by volume one rock type peridotite upper and lower sections Small percentage is liquid Core Innermost section 0 Outer core liquid iron alloy due to high temperature 0 Inner core solid ironnickel alloy due to high pressure despite even higher temp o The nature of the core generates Earth s magnetic field Moho Not a layer but the boundary between lower crust and upper mantle o Recognized by change in velocity of energy waves from earthquakes The Earth s Interior Lithosphere all of crust plus upper mantle rigid Asthenosphere portion of mantle that can ow not liquid Alfred Wegener Well known by fellow researchers of climate and the Earth Wegener made 4 initial observations His work combined with that of other scientists has developed into what is now known as the Theory of Plate Tectonics Also known as the theory of continental drift o The fit of the continents I Originally a supercontinent called Pangaea Glacial striations glacier picked up rocks that got stuck in the ice and scratched the surface of other rocks as the glacier moved 0 Wegener concluded that the areas with glacial striations must have once been closer to the South Pole and these regions were once near each other Swamps eventually form coal from buried plant material 0 There are strange coal deposit locations throughout the world 0 Paleoclimate data I Evidence of past environments differing from the current environments meant the continents must have been at different latitudes in the past at different distances from the equator o The distribution of fossils I The observed fossil pattern demonstrated the continents must have once all been together 0 Matching geologic rock units I Wagener concluded it was not coincidence that rock units matched across different continents now separated by vast oceans Paleomagnitism Study of the record of the Earth39s magnetic field in rocks sediment or archeological materials Geographic vs Magnetic North Pole Magnetic Northquot moves with time This means a magnet would point slightly different directions in the past south pole moves too If a rock forms from magma today Tiny magnetic crystals in rock will align themselves with today s magnetic north as the liquid turns to a solid If you study this rock 1000 years from now you would have a record of where magnetic north was in 2015 Rocks quotlockquot in the magnetic north south With this concept in mind Today scientists can study magnetic crystals in old rocks millions of years old and discover the direction of magnetic north south Water depth topography of oceanlake oor Harry Hess Sea Floor Spreading Magma would rise and form new oceanic crust and would push the old crust further out The old ocean oor sinks back into the mantle He thought that only the crust spread but this idea was incorrect Sea Floor Spreading and Magnetic Reversals New oceanic oor is created and old oor is separated and the polarity of the sediment created is based on the current polarity of the poles Age of Oceanic Rock Once technology allowed for rocks to be dated we found the youngest rock to be near midocean ridges Other Sea Floor Observations Ocean sediment was thinnest at midocean ridges and thickest at the ocean s edges Even the thickest sediment was too thin given the age of the Earth Even the oldest ocean crust was much much younger than the age of the Earth Oceanic crust has a very different chemistry than continental crust basalt vs granite respectively Plate Tectonic Theory The Earth s surface lithosphere crust upper mantle consists of about 20 rigid quottectonicquot plates Tectonic plates move relative to one another Tectonic plate movement causes continents to drift Wegener was right Interactions at the plate boundaries result in earthquakes volcanoes and mountain building Plate Boundaries Where two plates meet the plate boundaries is where the action occurs many geologic processes ofinterest o Divergent plates move away from each other 0 Convergent plates move toward each other I Three types of collisions Oceanic Continental plates Oceanic Oceanic plates Continental Continental plates 0 Transform plates move along side the other Plate movement Rates Additional Topics of Interest Continental Margin land ocean boundary 0 Passive 0 Active Hot spotslike a conveyor belt for making new islands if in the ocean Eg Hawaii Yellowstone Triple junction where 3 different plates combine together Tectonic Plates move but how Convection driven this theory is no longer accepted by most scientists Ridge push force force that drives plates away from a mid ocean ridge Slab pull force the force downgoing plates or slabs apply to oceanic lithosphere at a convergent margin Chemistry Basics Element a substance that is made up of only one type of atom Atomic number the number of protons in an atom An element is defined by the number of protons Atomic wei ht the number of protons neutrons in an atom carbon 6P6N 12 loin an atom with an unequal number of protons to electrons Cation positively charged ion has more protons than electrons Anion negatively charged ion has more electrons than protons Van Der Waals force the relatively weak attractive forces that act on neutral atoms and molecules and that arise because of the electric polarization induced in each of the particles by the presence of other particles 0 Very weak attraction Molecule two or more atoms bonded together the atoms can be the same or different Compound two or more different elements bonded together 0 All compounds are molecules but not all molecules are compounds A mineral is a naturally occurring solid formed by geological processes that has crystalline structure and a definable chemical composition Most Minerals are inorganic not formed by plants animals Polymorph Minerals with the same chemical composition but different crystal structures 0 Eg Diamond and Graphite carbon Calcite and Aragonite CaC03 Anhedral grains vs Euhedral Crystals Euedral crystals that are wellformed with sharp easily recognized faces Anhedral composed of mineral grains that have no well formed crystal faces or crosssection shape in thin section How do we identify minerals Examination of physical properties to identify minerals 0 Color Streak Luster Hardness Specific gravity Crystal habit form Cleavage Fracture Special properties OOOOOOOO Diagnostic Properties Color 0 Generally unreliable for mineral identification variable due to impurities in mineral chemistry Hardness 0 Resistance of a mineral to abrasion or scratching o All minerals are compared to a standard scale called the Mohs Hardness scale 0 Very useful for mineral identification Tetrahedral Forms By combining the SiOz tetrahedra together in different ways we can make different minerals Magma below the surface Lava above the surface Igneous rocks One of the three main rock types Formed through the cooling and solidification of magma or lava Examples 0 Granite magma o Rhyolite lava Intrusive igneous rock 0 Rock formed by the freezing of magma underground Extrusive igneous rock 0 Rock formed by the freezing of lava on the Earth s surface or ocean oor Temperature and pressure increase with depth Crystallization Rate Molten material cools and solidifies quicker at the Earth s surface Crystallization rate decreases with depth Crystallization Rate and Igneous Rock Temperature 0 Rhyolite o Finetextured Aphanitic Granite o Coarsetextured Phaneritic o A textural term for finegrained igneous rocks Mineral grains are too small to see with the naked eye 0 Indicates the molten rock solidified relatively quickly 0 Formed on the surface 0 A textural term for coursegrained igneous rocks Mineral grains are large enough to see with the naked eye 0 Indicates the molten rock solidified relatively slowly 0 Minerals had time to grow 0 Formed in magma Porphyritic Igneous Rock Texture Phenocryst a large crystal surrounded by a finergrained matrix in an igneous rock Porphyritic a textural term for igneous rock that has phenocrysts distributed throughout a p finer matrix L 39 r r r Indicates two stages of cooling larger crystals grew at depth but before molten rock had solidified a volcanic eruption brought the material to the Earth s surface where the remaining melt solidified quickly MagmaLava Chemistry Related to Igneous Rock MagmaLava ChemiStry and Properties Chemlstry Felsic Intermediate Ma c Ultrama c In general the chem of 1gneous rocks both 76 Silica content SiOZ 3 8 extrus1ve and 1ntrus1ve 1s h1ghly related to the chem of the magma lava from which it crystallized o For example if you find a felsic igneous rock it crystallized from a felsic magma or lava So how do we get magma in the rst ilace Magma forms in 3 steps 1 Explosive eruptions Mount St Hawaii Helens a High amounts of pressure can prevent materials from melting at their normal temperatures b Rock at great depths in the Earth s interior are often hotter than their melting temperature but remain a solid due to the pressure c If for some reason the pressure is decreased on these rocks they will melt in a process called decompression melting a Volatiles are chemicals such as water H20 and carbon dioxide C02 that can mix with solid rock within the Earth s interior b Volatiles help to break chemical bonds therefore adding volatiles to a quotdryquot rock will cause it to melt c Also known as quot uxquot melting 3 Heat transfer from rising magma a Rising magma brings heat from below and melts overlying or surrounding rock How do we end up with magma having different chemistry Felsic higher silica content Ultramafic magma lower silica content Ultramafic magma is mainly found at great depth and does not produce crustal rocks Intermediate magma is simply a mixture between mafic and felsic Felsic or silicic has the highest amounts of silica Mafic high amounts of magnesium and iron Factors controlling magma composition Source rock composition 0 The composition of a melt magma re ects the composition of the solid from which it was derived What happens if you slowly melt chocolate chip ice cream 0 The ice cream melts first but the chips are likely to remain solid until more heat is added This is the basic idea of partial melting At any given location in the Earth s interior only 2 to 30 of solid rock melts and forms magma More on this later but the felsic silicarich minerals melt first Therefore the new magma is more felsic than the original rock The remaining rock becomes more mafic Mafic rock may produce intermediate magma remaining rock may become ultramafic Pretend the raisins are felsic minerals and the If you remove raisins felsic minerals the bread are ma c minerals remaining loaf is more bread ma c minerals 1 Example 20 Felsic ff Felsic 80 Ma c I 5 Ma c When a rock is exposed to higher temperatures the felsic minerals melt first leaving the remaining rock more mafic The new magma is more felsic than the original rock While magma slowly moves upward it may incorporate the chemistry of surrounding rock that completely melt due to the heat of the magma If two or more bodies of magma with different chemistries combine in the subsurface the quotnewquot magma will have a composition different from the original chemistries The resistance to flow uid does not ow very well behaves like syrup uid ows easily behaves like water Factors controlling the rate of magma cooling Magma at the Earth s surface cools quickly Depth of magma intrusion magma deep in the Earth better thermos cools slower than shallow magma Shape and size of magma intrusion larger bodies of magma cool slower than smaller bodies 0 Intrusions with a large surface area cool more quickly more area for magma to lose heat Circulating water ground water passing through the magma removes heat like a car radiator Water freezes at 32 degrees Fahrenheit 0 9C Magma freezes at much higher temperatures 600 to 1200 QC Magma contains many different elements that eventually form various minerals each of which freeze at a different temperature Mafic minerals high Mg and Fe freeze first Felsic minerals high silica freeze last h pg 105 Temeu39e Bowen39s Reaction Series C mP 5i n Regimes rock types High temperature first to mating Quartz Intermediate diorlteandeeite Potassium feldspar Felsic Muscovute mica graniterhyolite I Copyright 2005 Pearson Prentice Hall Inc Lava ows sheets or mounts of lava that ow onto the ground surface or sea oor in molten form and then solidify 0 Review Viscosity resistance to ow 0 Melts with a high viscosity do not ow easily Review Factors affecting viscosity temperature volatile content silica content Hot lava with a hiih concentration of volatiles and low concentration of silica ows easily 1 Basaltic mafic chemistry low silica content 2 Andesitic intermediate chemistry medium silica content 3 Rhyolitic felsic chemistry high silica content Basaltic Lava Flow and Features Basaltic mafic lava ows have very low viscosity when first emerging from the ground due to high heat and low silica content Typically ow less than 10km the empty space left when a lava tunnel drains this happens when the surface of a lava ow solidifies while the inner part of the ow continues to stream downhill Hawaiian term a lava ow with a surface of smooth glassy ropelike ridges Hawaiian term a lava ow with a rubbly surface Columnar jointing a type of fracturing that yields roughly hexagonal columns of basalt when a dike sill or lava ow cools glassencrusted basalt blobs that form when magma extrudes on the sea oor and cools very quickly pressure plays role Andesitic Lava Flow Andesitic intermediate lava ows have higher viscosity due to higher silica content vs basaltic lava ow Typically ow less than 10 km Rhyolitic Lava Flow Rhyolitic felsic lava ows have highest viscosity due to highest silica content also tend to be coolest Typically ow less than 12 km 0 Lava quotdomequot forms Very blocky Pyroclastic debris from basaltic eruptions weak eruptions few more terms Latin for little stones Pea to plumsized fragments of glassy lava and scoria aka cinders Apple or largersized fragments Solidify while still in the air May become streamlined during ight Pyroclastic debris from andesiticrhyolitic Two types of lapilli may also be produced Volcanic Ash Some ash reaches high altitude and falls back to earth like snow gravity quickly returns some ash to the ground as a pyroclastic ow or glowing avalanche unconsolidated loose deposits of pyroclastic grains regardless of size Ash or ash mixed With lapilla that has been buried and transformed into solid rock Mobile mixtures of ash coarser debris and water Crater vs Fissure Eruption At a crater eruption lava spouts from a chimneyshaped conduit At a fissure eruption lava erupts as a curtain along a crack Volcanic Caldera Formation As an eruption begins the magma chamber in ates with magma During an eruption the magma chamber drains and the central portion of the volcano collapses downward The collapsed area becomes a caldera Later a new volcano may begin to grow within the caldera Three types of Volcanoes 0 Not explosive basaltic mafic lava relatively safe 0 sputters tephra out basaltic lava but more gas content relatively safe 0 Very explosive rhyolitic felsic lava dangerous Effusive Eruptions Mainly basaltic lavas low viscosity shield volcanoes Explosive eruptions Mainly rhyolitic lavas high viscosity stratovolcanoes Volcanic activity is NOT random Stratovolcanoes occur at convergent plate boundaries Shield volcanoes above hot spots Cinder cones develop at continental rifts each volcano type can occur in other settings volcanoes that are erupting have erupted recently or are likely to erupt soon volcanoes that have not erupted for hundreds or thousands of years but have the otential to erupt again i volcanoes that were active in the past but have shut off entirely and will never erupt again Example Devils Tower Wyoming Predictini Eruitions 0 As large volumes of magma moves up from below rock moves and cracks releasing energy that can be detected as small earthquakes 0 An increase in earthquake activity might suggest a future eruption 0 As large volumes of magma moves up from below more heat is brought near the surface 0 Melting snow on volcano summit might suggest a future eruption 0 As large volumes of magma moves up from below the volcano will actually bulge o Measurable bulging of volcano might suggest a future eruption 0 As large volumes of magma moves up from below more gases and steam will vent from the volcano 0 These gas increases might suggest a future eruption Volcanic eruptions remain largely unpredictable Despite all our advances in technology we are not able to give proper warning of upcoming volcanic eruptions Millions of people risk their lives every day due to their proximity to active volcanismincluding this guy Illustrates the different processes and paths as Earth materials change both on the surface and inside the Earth Principles Ke to Geolo ists the principle that the same physical processes observed today are responsible for the formation of ancient geological features the principle that younger layers of sediment are deposited on older layers of sediment thus a sequence of strata the oldest layer is at the base Sedimentary Rocks Sedimentary rocks tell us more about the history of Earth than any other rock type 0 Sedimentary rocks can tell us about I Past life plants and animals I Past environments rivers lakes and oceans I Pages of Earth s past Sandstone Classes of Sedimenta Rocks based on mode of origin Consists of cementedtogether solid fragments and grains from preexisting rocks 0 Example sandstone Formed from material such as shells by living organisms 0 Example coquina produced Formed from carbonrich relicts of 0 Example Coal Formed from minerals that precipitate from water solutions 0 Example Limestone Clastic Sedimentary Rocks formation fundamental steps are involved with the formation of clastic sedimentary rocks 0 rock fragments clasts detritus formed by the disintegration of bedrock in response to physical and chemical weathering o breaking of bedrock into smaller pieces chemistry of rock is not changed 0 bedrock is broken down as chemical reactions change chemistry of preexisting rock 0 Both physical and chemical weathering can break bedrock down at the same time Clastic Sedimentary Rocks Formation Physical Weathering Breaking of rocks into smaller pieces How does this happen 0 expansion of water in cracks by freezing wedging the rock apart as pressure is decreased due to removal of overlying rock by erosion igneous metamorphic rock expands and fractures in large sheetlike layers 0 rapid heating and cooling of a rock s surface resulting in more rapid expansion and contraction of the rock surface than the rock interior 0 the cracking and expansion of rocks as a result of plant growth and animal activity Clastic Sedimentary Rocks Formation Chemical Weathering those processes which occur when air and water chemically react with rock to alter its composition and mineral content 0 Includes dissolution hydrolysis and oxidation 1 o The dissociation of a mineral into its constituent ions as it dissolves in water 2 o The chemical reaction of a mineral with molecular oxygen 02 resulting in decomposition of the mineral I Example Oxidation of Fe in minerals resulting in the formation of hematite Fe203 3 0 Water reacts with a mineral to form a new mineral with water as part of the crystal structure I Example weathering of feldspar minerals by hydrolysis to form Clay minerals Clastic Sedimenta Rocks Formation Factors affecting rates of weathering fractures in rock gt Calcite dissolves in weakly acidic solutions gt Silicate minerals weather in same order as order of crystallization Bowen s Reaction Series 3 Chemical weathering most effective in warm moist climates Clastic Sedimentary Rocks Formation 0 Combination of processes wind water ice gravity that separate rock pieces from bedrock and carry it away is breakdown of the bedrock the erosion is separating and removing those pieces from bedrock o The movement from one location to another of clasts from one location to another by wind water or ice 0 Process by which sediment clasts settles out of the transportation medium water ice wind 0 Transportation of loose sediment into solid rock Typically involves burial of sediment compaction loss of water air and cementation calcitequartz Clastic Sedimentary Rocks Classi cation Five useful characteristics for describing clastic sedimentary rocks Clast Size 0 Size refers to the diameter of clasts making up a rock I Largest coarsest to smallest Finest Boulder cobble pebble sand silt clay Clast Composition 0 Refers to the make up of clasts in sedimentary rock what the pieces are made of I Clasts are often individual minerals grain of quartz or rock fragments multiple minerals Angularity and sphericity o Angularity indicates the degree to which clasts have smooth or angular corners and edges 0 Sphericity refers to how close the clast is to being a sphere ball Sorting o The degree to which the clasts in rock are all the same size or include a variety of sizes I sedimentary rocks have particles the same size I sedimentary rocks have various size particles Biochemical Sedimentary Rocks Various Types rock composed of primarily calcium carbonate which is either calcite or aragonite and once made up the shells for once living organisms rock composed of primarily cryptocrystalline quartz very very small grains which was once the shell of silicasecreting plankton Cold water environments Organic Sedimentary Rocks Primarily coal Chemical Sedimentary Rocks Bonneville Salt Flats ocean has right ingredients in it that once it starts to evaporate it becomes more salty and eventually creates a at bed of salt once the water completely evaporates hot water seeping through the ground that dissolves away preexisting rock and may deposit new rocks 0 Mammoth Hot Springs Yellowstone Sedimentary Structures A characteristic of sedimentary deposits that pertains to the character of bedding and or the surface features of a bed a single layer of sedment or sedimentary rock with a recognizable top and bottom 0 Bed surface marks I Mud cracks dry clay that has contracted over time and creates cracks I Trace fossil ex Footprints left by something that have almost been cast into rock the boundary between two beds several beds together the overall arrangement of sediment into a sequence of beds Ripple marks shows the movement of the current in the past Cross bedding movement of sand over a dune or ripple that creates a new dune crest a submarine underwater avalanche of sediment and water that speeds down a submarine slope a layer of sediment deposited by a turbidity current in which grain size varies from coarse at the bottom to fine at the top A shows the distribution of formations past environments Each color represents a speci c formation What type volcano is Olympus Mons What is a Metamorphic Rock Shield Largest known volcano in solar system Mars Metamorphism Example Igneous Metamorphic Metamorphlsm occurs w1th0ut the rock f1rst Rock Rock becoming a melt or sediment Hot water can also play a role NOT MELTING THE ROCK pressure Granite Gneiss the original rock from which a metamorphic rock formed In the example above granite is the protolith James Hutton Father of Modern Geology Developed the principle of uniformitarianism Was puzzled by certain rocks that seemed to have been formed as other rocks do but had been distorted in structure Rock Metamorphism Basics Solid state change due to change in preexisting rock s environment 1 Temperature change 2 Pressure change 3 Compression and shear become relevant 4 Hot water hydrothermal uid added to the system 5 Or a combination of one or more Environmental change produces new minerals that did not occur in protolith andZor produces a new texture Changes to Protolith Environment Increase temperature addition of heat helps to break chemical bonds allowing atoms to move and form new bonds which means new minerals Increase pressure tremendous pressures can cause atoms to pack more closely together sometimes forming new minerals Increase pressure and temperature certain minerals are stable at specific temperatures and pressures 0 Changing these variables promotes new mineral formation Exposure to very hot water hydrothermal uid from slide 16 metasomatism the process of changing a rock s chemical composition by reactions with hydrothermal uids Compression and Shear rce is applied down on an object example gravity force is applied to the sides of an object example convergent plate boundary force is applied in opposite directions on an object example pushing a deck of cards to one side or the other 339 Results of Compression and Shear o Equant Grains roughly same dimensions in all directions 0 Inequant Grains dimensions are not the same in all directions 0 Preferred Orientation alignment of inequant grains 0 The arrangement of grains formed as result of metamorphism specific new minerals grow only under metamorphic temperatures and pressures parallel alignment of platy minerals such as mica and or the presence of alternating lightcolored and darkcolored bands Metamo hie Processes 1 h 0 v Changes the shape and size of grains without changing the mineral chemistry grains ten to get bigger but not always 0 v Changes one mineral to another mineral of the same composition but different crystalline structure atoms rearrange 3 339 Results in new minerals that differ different chemical composition from those of the protolith 4 339 In the presence of water grains are dissolved on the sides undergoing more pressure and precipitate new mineral where the pressure is lower water helps atoms move easierquicker 5 0 v Grains change shape texture without breaking due to compression at high heat and soft plasticlike nature of rock Two Fundamental Classes of Metamorphic Rocks 1 metamorphic rocks distinguished by their component minerals grain size and by the nature of their foliation Ex Gneiss 2 metamorphic rocks primarily divided up by their component minerals what it is made of Ex Quartzite Common Examples of Foliated Rocks 1 Slate I Finegrained foliated metamorphic rock I Protolith shale or mudstone high clay content I Relatively low pressures and temperatures I Strong foliation slaty cleavage breaks easily into sheets 2 Phyllite I Finegrained with foliation caused by the preferred orientation of very finegrained white mica I Protolith slate neocrystallization of clay to produce white mica I Relatively low pressures but higher temperatures I Silky sheen called phyllitic luster 3 Metaconglomerate I Same metamorphic conditions as slate and phyllite pressure solution and plastic deformation atten pebbles and cobbles into pancakelike shapes I Alignment of clasts pebblescobbles defines foliation I Protolith conglomerate 4 Schist I Mediumtocoarsegrained I Foliation schistosity which is defined by the preferred orientation of large mica akes I Forms at higher temperatures than phyllite I Various protoliths 5 Gneiss I Typically composed of alternating light and dark bands with each band having a specific composition mafic vs felsic minerals I Foliation is gneissic banding which gives it a stripped appearance I Protolith had alternating beds of sandstone and shale or caused by extreme amounts of shearing rock ows like plastic I Various protoliths 6 Migmatite I Extreme conditions where gneiss may begin to melt but the partial melt quickly freezes resulting in part igneous part metamorphic rock Examples of Mica I Range of colors but has perfect cleavage in one direction sheetlike I Can be associated with metamorphic rocks Nonfoliated Metamorphic Rocks Common Examples 1 Hornfels I Contain a variety of metamorphic minerals which is based on minerals found in protolith and the temperature pressure of metamorphism 2 Quartzine I Protolith is pure quartz sandstone quartz grains recrystallize creating new grains sugary texture 3 Marble fossiliferous limestone marble I Protolith is limestone which r recrystallizes so that fossil 39 shells pore spaces grains and cement become a solid mass of calcite Degree of Metamorphism I Metamorphic grade indicated the intensity of metamorphism or the degree of metamorphic change 0 Low or high grade Increasing pressure Geologic Setting of Metamorphism 1 Contact thermal gt Temp of the protolith rises due to heat transfer from nearby magma gt Hydrothermal uids also play a role in metamorphosis gt The zone of alteration that is in contact with the magma is called metamorphiccon tact aureole Contact Metamorphism Aureole gt Does not involve increase in pressure and differential stress gt Metamorphic Contact Aureole zone of alteration that varies in width depending on the size and shape of the magmatic intrusion as well as the amount of hydrothermal circulation present 2 Burial gt Metamorphism due only to the consequences of very deep burial 815km gt Temperature and pressure increase with depth gt Lowgrade metamorphism 3 Dynamic gt Occurs at faults surface on which one piece of crusts slides at great depth gt10 Km gt Minerals in warm rock recrystallize get smaller and form the highlyfoliated p y K metamorphic mylonite 39 quot 7 Mymitehas gt Form due to shearing alone H verytmygrams39 Shear zone iginalrock 4 Dynamothermal regional gt Occurs during mountain building convergent plate boundary gt Some rock is pushed up mountains while some rock is pushed down Increased temp with depth Increased pressure with depth Increased compression and shear due to convergence gt Grade of metamorphism increases with depth gt Eventually mountains are eroded away and metamorphic rocks formed at depth rise and are visible at the Earth s Surface gt LARGE SCALE 5 Hydrothermal gt Chemical alteration caused when hot ionrich uids circulate through cracks gt Common at midocean ridges 6 Subduction Zones gt Produces metamorphic rock called blueschist gt Rare combination of high pressure but low temperature 7 Shock gt Shock waves caused by highenergy events such as a meteorite impacts can change minerals quartz changes to coesite Earthquake 0 An episode of ground shaking Q How many seismograph locations do you need to determine Where an earthquake originated A3 Causes of Earthquakes Sudden fracture on which sliding occurs Sudden Sudden change in the arrangement of atoms in the minerals of a rock Movement of magma in a volcano Explosion of a volcano Giant landslide Meteorite impact And underground nuclearbomb test Hi ocenter the ilace underground Where rock breaks and generates earthquake waves point on the surface of Earth directly above the focus Where the earthquake originates A fracture crack in the Earth s surface on which sliding movement occurs Fault basics Match the de nition With the type of fault 1 Normal faults A One block literally slides past another no vertical displacement 2 Reverse faults B Form during shortening of the crust steep 3 Thrust faults C Form during extension of the crust 4 Strikeslip fault D Also form during shortening gentle slope V 3917 6I 39E 8 39Z 3 39l 3319MSUV the amount of movement or slip across a fault plane a small step on the ground surface Where one side of a fault has moved vertically With respect to another New Fault Formation Stress a push pull or shear applied to a material Elastic Strain a change in shape of a material that disappears instantly when stress is removed Existing Fault Friction the force that resists sliding on a surface Fault terms Stickslip behavior stopstart movement along a fault plane caused by friction stick which prevents movement displacement until stress builds up sufficiently slip Elasticrebound theory the concept that earthquakes occur when rock elastically bends until it fractures the fracturing generates earthquake energy and decreases the elastic energy stored in the rock Foreshocks and aftershocks Foreshock the series of smaller earthquakes that precede a major earthquake Aftershock the series of smaller earthquakes that follow a major earthquake Seismic Waves Match the correct term with the de nition 1 Body Waves A Seismic waves that travel along the Earth s surface 2 Surface Waves B Compressional move through Earth s interior fast velocity nondestructive travel through both liquids and solids 3 PWaves C Seismic waves that pass through the interior of Earth 4 SWaves D Destructive cause ground to ripple up and down 5 LWaves E Most destructive waves cause ground to ripple back and forth 6 R Waves F Shear pass through Earth s interior moderately fast velocity nondestructive travels through only solids 1399 EI 399 d Va 399 With ISIGMSHV Body Wave Velocities Pwaves travel faster than swaves and are the rst to be recorded on seismographs Velocity of waves varies and depends on the type rock sediment through which they are passing Surface Wave Velocities L waves travel faster than R waves but surface waves travel much slower than body PampS waves Surface waves are last to be recorded by a seismograph Seismograph Instrument that can record the ground motion of an earthquake 0 Can tell us an earthquake is occurring 0 Provides data to determine earthquake epicenter 0 Provides data to determine intensity of earthquake De ning the size of an earthquake Mercalli Intensity Scale 0 Italian scientist Giuseppe Mercalli Richter Scale magnitude scale 0 American Scientist Charles Richter I Quantative measurements but works best with shallow earthquakes close to seismograph Momentmagnitude scale a numerical representation of the size of an earthquake that takes into account the area of the fault that slipped the amount of slip and the strength of the rock that broke Where do earthquakes occur Plate boundaries I Shallow earthquakes I Shallow intermediate and deep earthquakes I Shallow earthquakes Continental rifts 0 Shallow earthquakes similar to divergent plate boundaries but quakes occur near populated areas since on land Collision zones Intraplate earthquakes We make longterm predictions for example San Francisco will experience a major earth uake within the next 100 years We make shortterm predictions for example we cannot say a major earthquake will hit San Francisco on July 29 2016 0 Its not a matter of quotifquot but rather when Principles Superposition the principle that younger layers of sediment are deposited on older layers of sediment thus a sequence of strata the oldest layer is at the base Original Horizontality the principle that sediments are deposited in nearly horizontal layers 0 Rocks found may include sandstone shale etc Tilted rock Foliated Rock 0 May include quartzite slate etc o Metamorphic rocks Q In a normal fault is the hanging wall moving up or down A Hanging wall moves Orogen orogenic belt a linear range of mountains Orogeny a mountain building event may last tens of millions of years Match the key words with the proper de nitions 1 Uplift A A bend or wrinkle of rock layers folds 2 Deformation form from a consequence of ductile deformation 3 Joints B The upward vertical movement of the ground surface that occurs during mountain 4 Faults building C A change in the shape position or 5 Folds orientation of a material by bending breaking or owing D Naturally formed cracks fractures in rocks E A fracture on which one body of rock slides past another V 399 El 3917 I 39E D 39Z 8 39l 3SJQMSUV Strain The change in shape of an object in response to deformation ie l 1 Stretching a Rock becomes longer 2 Shortening a Rock becomes shorter 3 Shear a Rock becomes tilted with change in angular relationships Brittle vs Ductile Deformation Brittle deformation the cracking and fracturing of a material subjected to stress chemical bonds break ceramic plate Ductile plastic deformation the bending and owing of a material without cracking or breaking subjected to a stress dough 0 New chemical bonds are quickly formed when old bonds break Factors Controlling Deformation Type Temperature warm rocks tend to deform ductilely while cold rocks tend to deform brittlely Pressure increased pressure causes more ductile deformation Higher pressure makes it harder for rock to separate into segments Deformation rate slow deformation rate allows for ductile deformation A sudden rate of deformation will act brittlely Composition some rocks are softer than others and are more capable of deforming ductilely Brittleductile transition Rocks at the Earth s quotsurfacequot 1015 km tend to have brittle behavior Rocks below this depth tend to have ductile behavior Boundary between brittle and ductile material is known as the brittleductile transition Stress Stress Force applied per unit area Compression takes place when a rock is squeezed Tension occurs when a rock is pulled apart Shear stress develops when one side of a rock body moves sideways past the other side Pressure refers to a special stress condition in which the same push acts on all sides of an object Stress 7 39 Strain Stress causes strain change in shape Shear causes shear strain Joint 7 39Fault Both joints and faults are quotcracksquot or quotfracturesquot in rock but movement does not occur along a joint All faults are joints but not all joints are faults Faults Surfaces of Slip more cartoons Faults Surfaces of Slip Reverse thrust and normal faults quotdipslip faultsquot Transform Faults strikeslip faults 0 Right or left lateral displacement Left Lateral Right Lateral Axial plane Hinge line Fold Terminology Hinge Line portion of fold where curvature is greatest 0 m sides of folds show less curvature 0 Axial plane surface imaginary surface that cuts through hinges of multiple layers splits fold down the quotmiddlequot 0 Anticline fold with archlike shape limbs dip away from hinge think quotAquot for anticline 0 Rock farthest out is youngest Synchne 0 Fold with throughlike shape limbs dip toward hinge think quotSquot for smile syncline Youngest rock is at the center Anticlines and Synclines happen together Monocline Fold with stairstep shape only one dipping limb Dome Fold with overturned bowl shape limbs dip away from center 0 Youngest rock is outer edge Basin 0 Fold with bowl shape limbs dip toward center Youngest rock is at the center Plunging Anticline If the hinge is horizontal the fold is called a nonplunging fold but if the hinge is tilted the fold is called a plunging fold anticline syncline Symmetrical vs Asymmetrical Folds Symmetrical folds go straight up and down Asymmetrical folds have a more diagonal shape Overturned folds have an extreme diagonal shape Measuring Dip The angle of inclination of a rock unit or fault measured from a horizontal plane Includes both a angle measurement ie how much its tilted and a direction ie which direction is it tilted Measuring Strike WWW manquot 13ka Perpendicular to dip 39 The compass direction of the line Strikedip rt 7 39x9pqecnon produced by the intersection of a 39 symbg39 A rock layer or fault with a gt430 N horizontal plane rm A mp angle 4m o Generally expressed as an angle 3 quotquot 39v39 relative to north measured Waterline A 39f39fquotti clockwise 7 N g 1 Number typically is not shown 3if Wquotri39 fufng a 1 quot1 lri it 111353913951 1 i77f quotf quot 27 j w y glut Relative vs Numerical Age Relative The age of one geologic feature with respect to another older than younger than Numerical The age of a rock or structure as specified in years referred to as absolute agequot in older literature Original continuity 0 Sediments generally accumulate in continuous sheets they will either pinch outquot or run into a preexisting feature 0 Layers that are cut are due to subsequent erosion Crosscutting relationships 0 The relative age of rock can be determined by looking at which rock or structure cuts another the feature that has been cut is older Baked contacts 0 An igneous intrusion bakes metamorphoses surrounding rocks The rock that has been baked must be older than intrusions Inclusions o The rock containing inclusions must be younger The rock that makes up the inclusions must be older Unconformities Gaps in the Record A boundary between two different rock sequences representing an interval of time during which new strata were not deposited and or were eroded missing timequot o mular unconformity I An unconformity in which strata blow were tilted or folded before the unconformity developed strata below the unconformity therefore have a different tilt than the strata above 0 Nonconformity I A type of unconformity at which sedimentary rocks overlie basement older intrusive igneous rocks and or metamorphic rocks 0 Disconformity I An unconformity parallel to the two sedimentary sequences it separates Q Is there a single location on Earth that contains a complete record of Earth history A No How do geologists describe strata Stratigraphic strat Column a crosssection diagram of a sequence of strata summarizing information about the sequence Stratigraphic formations a sequence of beds of a specific rock type or group of rock types that can be traced over a fairly large region The Redwall Limestone is a formation mainly limestone The Supai Group is a formation consisting of multiple rock types Contact the boundary surface between two formations this is one of many types of geological contacts Lithologic Correlation Correlation matching of formations to other nearby formations based on similarities in rock types Fossil Correlation Correlation matching of formations to other distant formations based on similarities in fossil type age The Geolo ic Column The geologic column has been pieced together using information from millions of local stratigraphic columns The column is divided into segments each of which represents a specific interval of time The largest subdivisions break earth history into Eons which include the Hadean Archean Proterozoic and Phanerozoic Phanerozoic means visible life The Phanerozoic Eon visible life is divided into E o Cenozoic era recent life 0 Mesozoic era middle life 0 Paleozoic era early life m are divided into E Eras are divided into periods 0 Period names come from area where rocks of that age are well represented Devonian Devon England or an important characteristic of thmat time Carboniferous period contain a lot of coal Periods are divided into Epochs Numerical Age Study of rocks ages is called geochronology The process of determining the numerical age of rocks is called radiometric dating isotope dating Isotope different versions of a given element carbon that have the same atomic number but different atomic weights same number of protons but different number of neutrons Stable they will always retain the same number of protons and neutrons essentially forever Unstable radioactive they change with time to a different element Radioactive Decay Radioactive Decay the process by which a radioactive atom undergoes fission or releases particles thereby transforming into a new element Parent isotope the original isotope that undergoes decay Daughter isotope the product of the decay of a parent isotope Halflife the time it takes for half of a group of radioactive element s isotopes to decay example 5000 years Parent Daughter b The ratio of parenttodaughter isotopes changes with the passage of each successive halflife Toda 5000 s 10000 s 15 000 s 20 000 Slow Start Actionpacked Ending Based on our current scientific understanding the first part of Earth s history was devoid of life and an extremely hostile environment About 542 million years ago there was an explosion in the diversity of living organisms Many quotmass extinctionsquot have helped to shape the history of life on earth The Hadean Eon 4570 3850 million years ago Spans Earth formation to first appearance of continental crust Hell on Earthquot Moon formation questions still remain about the environment The Archean Eon 3850 2500 million years ago Begins with the first appearance of continental crust First life thought to be present 3800 3500 0 Chemical molecular fossils or biomarkers o Isotope signatures 0 Fossil forms fossilized bacteria Stromatolites distinctive mounds of sediment produced by mats of cyanobacteria Atmosphere high in carbon dioxide and nitrogen little oxygen Proterozoic Eon 2500 524 million years ago Spans almost half of Earth s history Larger plates and continents formed 90 of continental crust Atmosphere became oxygenrich Shields formed broad lowlying region of exposed Precambrian rock Cratonic platforms formed strata burying shield Rodinia an early supercontinent Ediacaran fauna first multicellular organisms Great oxygenation event dramatic increase in atmospheric oxygen around 2400 million years ago due to photosynthetic organisms producing oxygen and other environments not be able to absorb oxygen Snowball Earth a proposed state of Earth in which Glacial conditions were found globally 0 Many organisms went extinct 0 C02 from volcanic activity is thought to have warmed earth enough to melt 1ce Phanerozoic Eon 524 million years ago to present Diverse organisms with shells or skeletons Supercontinents formed and broke apart Mountain ranges formed happening today Subdivided into 3 Eras o Paleozoic o Mesozoic o Cenezoic The Early Paleozoic Era Cambrian Ordovician Periods 542 444 million years ago Epicontinental seas shallow seas that may have supported many organisms 20 million year period of dramatic diversification of life based on fossil record Conodonts resemble tiny jaws may have belonged to tube like animals 0 Trilobites The Middle Paleozoic Era Silurian Devonian Periods 444 359 million years ago On land vascular plants with woods tissues seeds and veins for transporting food and water rooted for the first time 0 Plants were able to grow to larger sizes than previously T iktaalik rst amphibian to crawl onto land and inhale air with lungs The Late Paleozoic Era Carboniferous Permian Periods 35 9 251 million years ago Relatively cooler sea level dropped land exposed and high amounts of organic material produced eventually coal 0 Pangea formed First reptiles appear 0 gt95 of all marine life went extinct The Early and Middle Mesozoic Era Triassic Jurassic Periods 251 145 million years ago Pangea starts to break apart was together for 100 million years Iurassic period dinosaurs TRex lived during the Cretaceous Period not Iurassic The Late Mesozoic Era Cretaceous Period 145 65 million years ago Sea level rose dramatically ooding much of the continents Atmosphere was very warm A shallow sea divided presentday North America Very active west coast Not just dinosaurs 0 Giant turtles 0 Larger animals 0 quotmodernquot fish appear The KT boundary event 0 K Cretaceous Period T Tertiary Period 0 150million year long rein of dinosaurs ended quotinstantlyquot o 90 of plankton species and 75 of plant species went extinct Chicxulub Crater The last ice age 0 Ended about 11000 years ago GEO 101007 Exam 4 Study Guide Chapter 14 Streams and Floods The Geology of Running Water 1 Water Table A Occurs when a uid ows in parallel layers with no disruption between layers 2 Stream B Running water removes loose fragments of sediment 3 Channel C A trough dug into the ground surface by owing water 4 Flood D Larger solid particles sand pebbles or cobbles that bounce or roll along stream oor 5 Headward Erosion E Water seeping through rock surrounding stream channel dissolves certain minerals and transports these ions down the stream 6 Continental Divide F Occurs when a uid ows in parallel layers with no disruption between layers 7 Laminar Flow G A ribbon of water that ows in a channel 8 Scouring H Refers to the maximum particle size a stream can carry 9 Breaking and Lifting I The process by which a stream channel lengthens up its slope as the ow of water increases 10 Abrasion J Small solid particles silt or clay size that swirl along in the water without settling to the oor of the channel 11 Dissolution K The boundary approximately parallel to the Earth s surface that separates substrate in which groundwater lls the pores from substrate in which air lls the pore 12 Dissolved Load L Running water can break clasts of solid rock off the channel oor or walls or may lift clasts of the channel oor 13 Suspended Load 14 Bed Load 15 Stream Competence 16 Stream Capacity 17 Turbulent Flow Draining the Land M A highland separating drainage that ows into one ocean from drainage that ows into another N Running water containing sand to gravel size particles acts like sandpaper and grinds away at the channel oor or walls 0 An event during which the volume of water in a stream becomes so great that it covers areas outside the stream s normal channel P Running water dissolves soluble minerals as it passes and carries the minerals away in solution Q Refers to the total quantity of sediment it can carry depends on competence and discharge Precipitation rain snow hail brings water to land surface Groundwater springs also bring water to the land surface Gravity pulls surface water downhill into a stream channel which is a trough in the surrounding substrate Stream Formation 2 3 4 Drainage Network basin An array of interconnecting stream that together drain an area 5 types 0 Dendritic Rectangular Trellis Radial o o o 0 Parallel 1 Precipitation rain occurs Sheetwash ows downhill Flowing water digs tiny channels called rills Rills downcut develop into stream ow The geology rock type of land surface is the major control over the type of drainage network that develops Drainage Divides and Basins A highland or ridge that separates one drainage basin network from another GEO 101007 102815 Permanent vs Ephemeral Streams Permanent Streams Ephemeral Streams Water ows all year Do not ow all year Bed oor of channel is at or below Bed oor of channel is above the water table the water table Humid or temperate climates Dry climates o Suf cient rainfall 0 Low rainfall 0 Low evaporation 0 High evaporation Discharge varies seasonally Flows mostly during rare ash oods Stream Discharge Discharge area of the stream times average stream velocity Measuring water ow velocity can be dif cult 0 Not all water ows through a streamriver at the same speed Erosion Ef ciency of erosion is a function of velocity volume and sediment content of water 0 Small volume slowmoving clear water I Not ef cient at erosion 0 Large volume fastmoving turbulent sandy water I Very ef cient at erosion o A lot of erosion can occur during a ood more energy How do streams transport sediment Geologists refer to the total volume of sediment carried by a stream as its sediment load Sediment Deposition High energy fast moving water sediment erosiontransportation Low energy slow moving water sediment deposition Typically streamriver energy decreases slowly When this happens the larger clasts pebbles are deposited rst then mediumsize clasts sand and nally small clasts siltclay Sorting occurs Fluvial deposits alluvium sediment deposited in a stream channel along a stream bank or on a oodplain Point bar a wedgeshaped deposit of sediment on the inside bank of a meander w a wedge of sediment formed at a river mouth when the running water of the stream enters standing water the current slows the stream loses competence and sediment settles out Stream gradient The slope of a stream s channel in the downstream direction Longitudinal profile a crosssection image showing the variation in elevation along the length of a river GEO 101007 102815 Base Level The lowest elevation a stream channel s oor can reach at a given locality Ultimate base level is sea level sea level can move up and down 0 A lake represents a local base level 0 A stream tries to erode down to base level slow process In general a stream cuts down into the ground in the headwaters and cuts from side to side near the mouth Meander a snakelike curve along a stream s course Alluvial Fan A gently sloping apron of sediment dropped by an ephemeral stream at the base of a mountain in arid or semiarid regions Braided stream A sedimentchoked stream consisting of entwined subchannels Chapter 15 Restless Realm Oceans and Coasts 1 Bathymetry A Low area between waves 2 Abyssal Plain B The bending of the waves as they approach the shore at an angle 3 Seamounts C As the lithosphere moves away from the midocean ridge spreading centers it cools down and sinks creating a at section of ocean oor 4 Current D The elevation difference between sea level at high tide and low tide 5 Coriolis Effect E Time interval between passage of two successive crests 6 Gyre F A wellde ned stream of ocean water 7 Thermohaline Circulation G Hotspot volcanoes nonplate boundary related that do not rise above sea level 8 Tidal Reach H Top of the wave GEO 101007 9 Crest 10 Trough 11 Base 12 Wave Refraction 13 Fjord 102815 I A deep glacially carved Ushaped valley ooded by rising sea level J Variation in depth K A large circular ow pattern of ocean surface currents L The rising and sinking of water driven by contrasts in water density which is due in turn to differences in temperature and salinity this circulation involves both surface and deep water currents in the ocean M The de ection of objects winds and currents on the surface of the Earth owing to the planets rotation What does crust have to do with oceans Compared to continental crust oceanic crust is more dense thinner and younger These differences result in the surface of the oceanic crust having a lower elevation than continental crust Ocean Floor Features Passive Continental Margin Continental shelf wide Continental slope Continental rise Passive Continental Margin Relatively shallow water Relatively at Active Continental Margin Continental shelf narrow Continental slope steeper Trench Abyssal Plain Submarine canyons Seamounts Mid ocean ridges A Passive Continental Margin Continental shelf Continental Stops Continental rise Continental won I mogemmd GEO 101007 102815 appears steeper than It really Is I 1 Active Continental Margin Deep trenches Mariana Trench Ocean Water and Currents Salinity the degree of concentration of salt in water Ocean Water Salinity Variation Ocean water salinity variation is a function of 0 Water temperature warm water can hold more salt I Tropics are generally warmer due to more solar radiation I A large difference in water temperature with depth eXists near the tropics I Warm water from tropics is transported toward the poles by currents 0 Addition of freshwater from river runoff groundwater ice melt and direct rain 0 Evaporation rate at oceans surface 0 Ocean currents fast moving vs slow I Surface Currents are caused by interaction between wind and the surface of water Only affects the upper few hundred meters of water I Deep Currents are also in uenced by wind due to zones of upwelling and downwelling West 0035 West Coast Sommem Hemasphere Scnmm Hemsphme NOrthorly Ocean Deep Currents Rivers in the Sea Upwelling wind pushing water away from coast southern wind Downwelling wind pushing water toward the coast northern wind Rotation of Earth Rotation of Earth Wave Action Cause shear of wind blowing over the water surface Energy decreases with depth Copyngmzom pearso ren ceuau mo Wave morphology 39 o Crest Upwellmg Downwelllng 0 Through 0 Base Longshore Current and Longshore Drift o Responsible for sediment transport along coast GEO 101007 102815 F The Coastal Zone Mainland Backshore i Beach 39 Beach an accumulation of sediment found along V cm 7 fBe o 1 V i i landward margin of ocean r I Offshore Bars Submerged or partly exposed ridge of sand or c This profile shows the components of W h b h 39 i A coarse sediment that is built by waves offshore I e eac enmnmem quotde sacii39cie from a beach Breaking waves dig into the sand near the shore creating trough The excavated sand is deposited either on the beach or aside forming sandbar offshore bar Barrier island Baymouth spit Baymouth bar Barrier Islands w Longshore current N Sand Offshore piles of sane built above sea level Mud that is a result of high rate of sediment I Wetland depOSItlon due to wave and tlde aCtIVIty d Beach drift can generate sand spits and baymouth bars Sedimentation eventually fills in the region behind a baymouth bar Estuaries An inlet in which seawater and river water mix created when a coastal valley is ooded because of either rising sea level or land subsidence sinking Barbuilt estuaries 0 Form when a shallow lagoon or bay is protected from the ocean by a sand bar or a barrier island Coastal Plain Estuaries o Formed at the end of the last ice age between l0000l8000 years ago As glaciers receded and melted sea levels rose and submerged lowlying river valleys Organic Coasts A coast along which living organisms control landforms along the shore Coastal wetlands salt marshes and mangroves Coral reefs GEO 101007 Chapter 16 A Hidden Reserve Groundwater 1 Groundwater 2 Water Table 3 Unsaturated Zone 4 Saturated Zone 5 Aquitard 6 Aquifer 7 Con ned Aquifer 8 Unconfmed Aquifer 9 Perched Aquifer 10 Infiltrate 11 Recharge area 12 Discharge area 102815 A Seep down into B The region below the water table where pore space is filled with water C A mound of groundwater becomes trapped above a localized aquitard that lies above the regional water table D Sediment or rock that does not transmit water easily and therefore retards slows down stops the motion of water typically has both low porosity and permeability E An aquifers that is separated from the Earth s surface by an overlying aquitard F A location where water enters the ground and infiltrates down to the water table G Water that resides under the surface of the Earth mostly in pores and cracks of rock or sediment H A spring that emits water ranging in temperature from 30140 degrees C I An aquifer that intersects the surface of the earth J The region of the subsurface above the water table pore space may contain some water and some air K Sediment or rock that transmits water easily has high porosity and permeability L The potential energy available to drive the ow of a given volume of groundwater at a location can be measured as an elevation above a reference GEO 101007 102815 13 Hydraulic Head M The boundary approximately parallel to the Earth s surface that separates substrate in which groundwater lls the pores from substrate in which air lls the pores 14 Oasis N A verdant green with grass etc region surrounded by desert occurring at a place where natural springs provide water to the surface 15 Hot spring 0 A location where groundwater ows back up to the surface and may emerge at springs Karst Landscape A region by underlain by caves in limestone bedrock the collapse of the cave creates a landscape of sinkholes separated by higher topography or of limestone spires separated by low areas Porosity and Permeability Porosity the total volume of empty space pore space in a material usually eXpressed as a percentage pores can become lled with water Permeability the degree to which a material allows uids to pass through it via an interconnected network of pores and spaces Perched Aquifer a mound of groundwater becomes trapped above a localized aquitard that lies above the regional water table Cone of Depression Land surface Well Groundwater Flow Gravity and pressure cause groundwater to ow groundwater can ow sideways and even upward Groundwater Flow 39 Radius of influence I Very slow compared to surface water Rate can vary from 4 to 500 meters per year 13 to 1640 feet per Pm 39gslr39 year 9 Aquifer Rate is a function the slope of the water table hydraulic head We Wequot and the permeability of the material through which the groundwater is owing Impermeable material Moves at a snail s pace Potentiometric surface Artesian Well A well in which water rises on its own Potentiometric surface the elevation to which water in an artesian system would rise 3quot 1 Flowing Standpipe Aquifer Nonflowing artesian well artesian well GEO 101007 102815 if unimpeded where there are owing artesian wells the potentiometric surface lies above ground Spring A natural outlet from which groundwater ows onto the ground surface Where the ground surface intersects the water table 11 a discharge area Various Types of springs Where owing groundwater collides with a steep impermeable barrier and pressure pushes it up to the ground along the barrier Where a perched water table intersects the surface of a hill Where downwardpercolating water runs into a relatively impermeable layer and migrates along the top surface of the layer to a hillslope Where a network of interconnected fractures channels groundwater to the surface of a hill Hot Spring Rock deposits Travertine a rock composed of crystalline calcium carbonate formed by chemical precipitation from groundwater that has seeped out at the ground surface Groundwater Concerns Change of groundwater ow direction Saltwater intrusion Ground subsidence 0 When intensive irrigation removes groundwater pore space in an aquifer collapses 0 As a result the land surface sinks leading to the formation of ground fissures and causing houses to crack Chapter 18 Amazing Ice Glaciers and Ice Ages 1 I Glacier A Breaking off of chunks of ice 2 E Sublimation B Sediment deposited at sea by melting 3 F Melting C A strip of till along the side margins of a glacier 4 A Calving D Cobble to boulder size clasts of rock found within till or random places where the glacier was once owing 5 J Moraine E Evaporation of ice into water vapor 6 C Lateral Moraine F Ice melts and liquid water ows away GEO 101007 7 G Medial Moraine 8 H Till 9 D Erratics 10 B Glacial Marine 11 K Glacial outwash 12 P Loess 13 M Glacial Lake Bed 14 L Varve 15 R Kettle Hole 16 Q Drumlin 17 Q Glacial Subsidence 102815 G A strip of till in the interior of a glacier parallel to the ow direction of the glacier formed by the lateral moraines of two merging glaciers H Unsorted sediment carried by ice deposited beneath at the side or at the toe of a glacier I A river or sheet of ice that slowly ows across the land surface and lasts all year long movement caused by gravity J A sediment pile composed of till glacial sediment deposited by a glacier K Till from the glacier toe that is transported and sorted by braided streams L A pair of thin layers of glacial lakebed sediment one consisting of silt brought in during the spring oods and the other of clay deposited during the winter when the lake s surface freezes over and the water is still M Fine grained sediments deposited in glacial lakes varves are common alternating thin layers of clay and silt N The process by which the surface of a continent rises back up after an overlying continental ice sheet melts away and the weight of the ice is removed still happening today in some areas 0 A streamlined elongated hill formed when a glacier overrides glacial till P Silt and clay size sediment transported away from glacier s toe and deposited some distance away from the glacier Q The sinking of the surface of a continent caused by the weight of an overlying glacial ice sheet GEO 101007 102815 18 N Glacial Rebound R A circular depression in the ground made when a block of ice calves off the toe of a glacier becomes buried by till and later melts Louis Agassiz Geologist from Switzerland Proposed that places in Europe that had random rocks showing up must have been a result of a glacier dropping the rocks as it melted Glacial Erratic Erratic o A boulder or cobble that was picked up by a glacier and deposited hundreds of kilometers away from the outcrop from which it was detached Ice frozen water is a mineral naturally occurring inorganic solid with a de nite chemical composition and regular crystal structure Layers of Snowfall Layers of snowfall are very much like layers of loose sediment With time and pressure from snow above snow akes recrystallize into solid ice Snow to solid ice Loose snow Granular snow Fim Finegrained ice Coarsegrained ice m o Compacted granular ice derived from snow that forms where snow is deeply buried if buried more deeply fim turns into glacial ice Formation of Glaciers Three criteria for glacier formation 1 Local climate must be cold enough that winter snow does not melt entirely away during the summer 2 There must be sufficient snowfall for a large amount of snow to accumulate 3 Slope of the surface must be gentle enough that the snow does not slide away in avalanches Types of Glaciers Two categories of glaciers 1 Mountain alpine shape controlled by topography of mountains ow from high to low elevation I Cirque 11 Valley 111 Ice caps IV Piedmont GEO 101007 102815 2 Continental vast ice sheets that cover thousands of square kilometers of continental crust today the only exists in Antarctica and Greenland How exactly do glaciers move Plastic deformation 1 Only occurs below 60 m 2 Grains change shape very slowly as new grains form while old grains disappear Basal sliding 1 Must be warm enough for water to build up at base of glacier 2 Water along base on glacier acts as a lubricant on which the glacier can move water decreases friction The rate of ice movement varies with time and within the glacier friction slows down movement where ice contacts rock sediment Crevasse Formation A large crack that develops by brittle deformation in the top 60 m of a glacier FIGURE 18 a an ml Luluquot n tml xi Q Oligin Glaciers are similar to bank accounts Deposits snowfall Glacial Equilibrium Withdrawals ablation V snowfall ablation Zone of accumulation Q deposits withdrawals Equilibrium line Zone of ablation Glacial Advance Terminus toe i snowfall gt ablation Ablation includes 39 I g deposits gt withdrawals o Sublimation evaporation of ice into if water vapor o Melting ice melts and liquid water ows away o Calving breaking off of chunks of ice GlaCial Retreat snowfall lt ablation lt Icebergs Emma N deposzts withdrawals ICC is 01111de in Shallow water but oats in fir H 341 deep water Sea Ice also contribute icebergs to ocean Ice formed by the freezing of the surface of the sea GEO 101007 102815 Plucking and Abrasion 1 quot u v 00 Plucking is chunks of bedrock being 39 plucked out by the moving ice U k3 o a Q 4 Abras1on 1s chunks of rock that has 1 o v already been plucked up into the 39 39 U L U o r o 39 39 Kl I 39 glac1er that move against the bedrock 39 P39 39 399 N J 39 J 1 V as the glac1er moves and cause w Roche abrasions 39 moutom e Pleistocene Epoch 26 mya to 11000 ya a01211151011mspsf39ieripst39ear 5116ra39ujlplull39tgd39rleswi39y Laurentide Ice Sheet an ice sheet that spread over northeastern Canada during the Pleistocene ice ages froctrohommoo 7 oaks 0quot Mr ismastran s or Glaciation glacial period A portion of an ice age during which huge glaciers grew and covered substantial areas of the continents Interglacia a period of time between two glaciations Holocene a period of geologic time since the last ice glaciation Chapter 12 Riches in Rock Energy and Mineral Resources The Sun energy Capacity to do work How much energy is stored in fossil fuels 1 barrel of oil 42 gallons 1667 kilowatthours 40 hours of pedaling per week 52 weeks per year for 801 years 1667 kilowatthours Energy and Resources Energy 0 The capacity to do work to cause something to happen or to cause change in a system Resource 0 Any material that can be of use either to make something or to provide energy Two types of resources Energy resources 0 A resource which can be used to produce heat and electricity or move machines Mineral resource 0 A resource which provides natural inorganic chemicals from which products can be manufactured Sources of energy Sun 0 Solar energy resulting from nuclear fusion reactions in the sun can be converted directly into electricity using solarenergy panels or used to heat water Gravity o Gravitational attraction between Earth and Moon causes tides water movement can be converted into electricity turbines Solar energy and gravity 0 Solar radiation heats both air and water resulting in wind and owing water after rain that can turn turbines Photosynthesis 0 Solar energy builds bonds in plants and the energy is released when these bonds are broken wood being burnt Chemical reactions 0 Inorganic chemicals that can burn to produce light and energy TNT hydrogen fuel cells Fossil fuels 0 Solar energy is stored up in organisms from long ago oil gas and coal are examples Nuclear fission o Splitting of certain atoms releases vast amounts of energy nuclear power plants nuclear submarines Earth s internal heat 0 Geothermal energy that can drive turbines heat within the Earth increases temperature of ground water Oil and Gas Oil and natural gas consist of hydrocarbons Hydrocarbons 0 Organic chemicals made of chainlike or ringlike molecules made of carbon and hydrogen atoms I Hydrocarbon type natural gas gasoline oil tar is a function of chain length How are hydrocarbons formed Hydrocarbon formation 0 Source rock I A rock organicrich shale containing the raw materials from which hydrocarbons eventually form 0 Kerogen I The waxy molecules into which the organic material in shale transforms when reaching 100 C At higher temps kerogen turns into oil 0 Oil shale I Shale containing 1530 kerogen misleading name 0 Oil window I A narrow range of temperatures under which oil can form in a source rock 90160 C o l60225 C natural gas 0 gt225 C graphite Hydrocarbon Reserve A known supply of oil and gas held underground not all rocks contain oil So we simply drill into source rock to extract oil Actually no Reservoir rock 0 A rock that contains or could contain an abundant amount of easily extractable oil and gas these rocks have high porosity and high permeability Porosity o The total volume of empty space pore space in a material usually expressed as a percentage Permeability o The degree to which material allows uids to pass through it via an interconnected network of pores and spaces Trap 0 A trap is a geologic configuration that accumulates and holds oil andor gas underground needs source reservoir and seal rocks 39 Seal rock 0 A relatively impermeable rock such as shale salt or unfractured limestone that lies above a reservoir rock and stops the oil andor gas from rising further FIGURE 123 Initially oil resides in the source rock Because it is buoyant relative to groundwater the oil migrates into the overlying reservoir rock The oil accumulates beneath a seal rock in a trap Present Temporary storage Transport will 391quot W li igiliii 39i 115 39i Past Types of Traps Anticline Trap Fault Trap Saltdome Trap Stratigraphic Trap Seal rock Reservoir rock Source rock a Anticline trap Oil and gas rise to the crest of the fold b Fault trap Oil and gas collect in tilted strata adjacent to the fault Faults Seal rock Reservoir rock Source rock c Saltdome trap Oil and gas collect in strata on the flanks of the dome beneath salt Seal rock Reservoir rock Stratigraphic quot pinchoutquot Source rock d Stratigraphic trap Oil and gas collect where the reservoir layer pinches it out Oil Exploration and Production Edwin Drake 0 He and his team were the first to ever drill into the Earth and extract oil on Aug 27 1859 Since then 2D seismic view 3D seismic view Oil Rigs Other types of hydrocarbons Natural gas Tar sands oil sands and oil shale Gas hydrates Environmental impacts of hydrocarbon use Green house and other dangerous gases are released into the atmosphere Oil spills Global warming 0 Etc A black brittle sedimentary rock that burns consists of elemental carbon mixed with minor amounts of organic chemicals quartz and clay 0 Coal and Oil do NOT have the same composition or origin Coal Formation Organic debris that eventually become coal come Ranks of Coal fr m l n m r O p a t zite ngnlte Subbltumlnous Bituminous AnthraCIte AS 563 level 363 a coal Swamp mlgrates Inland 7000 BTUlb 9000 BTUlb 12000 BTUlb 15000 BTUlb and the swamp s deposits are eventually buried by other strata 39 n A layer of peat accumulates beneath a swamp Upon burial the peat becomes lignite After further Formation Conditions gt burial lignite alters to form bituminous coal Low T P 399 T39 P Coal is found in sedimentary beds interlayered with Time of Formation gt other strata sandstone shale and limestone C gt Lowest Grade Highest Grade U 8 Coal U 8 Coal Environmental impacts of coal use Gases O C02 0 Sulfur gasesacid rains Mercury 0 It is part of the composition of the coal 0 Mercury is released easily because its compounds are volatile Ash 0 Contains trace metals such as selenium and uranium which leach wash out once ash is deposited Coal mining hazards Mining coal underground is dangerous mines collapse and miners have lung problems from breathing the coal dust Gas explosions often end tragically Nuclear power and energy Nuclear power plant 0 A reactor heats water which produces highpressure steam The steam drives a turbine that in turn drives a generator to produce electricity A condenser transforms the steam back into water Nuclear fusion 0 Fusing two light atoms into a heavier atom I Takes place in stars I Despite occasional claims of cold fusion this has never been replicated on earth Nuclear fission 0 Breaking heavy unstable atoms mostly 235U apart by subjecting them to a controlled ux of neutrons What does this have to do with geology 238U is most common 235U has to be concentrated through enrichment which is expensive Ancient streambed gravel deposits have the highest concentrations of uranium Environmental impacts of nuclear power Fukushima nuclear disaster in March 2011 0 Problems related to violent earthquake and related tsunami Nuclear power plants produce hazardous waste 0 No one wants the waste nearby 0 Where do we put it o How long should it be stored Geothermal energy obstacles faced Not a widespread energy source only feasible to drill in certain areas where heat is near the Earth s surface High installation costs Too much use can cool local rock and reduce steam production Dangerous gases can be released Most cost ef cient to provide energy for local area however station site may be in remote area Other energy sources Solar limitations Wind limitations Hydroelectric limitations Hubbert s Peak Hubbert39s Peak Oil Production 0 peak oil production Bill ions Peak oil discovery v end of r oul based economy Hubbert 39 N r geophysicist 2000 2100 0 peak oul production occurs when Pnce 0f 0quot the rate of producnon is equal to S10095 on the rate of consumption In 1956 Hubbert predicted that global oil production would reach maximum around the year 2000 and trigger an energy crisis with power blackouts and rising costs of energy and fuel Chapter 17 The Geology of Deserts Deserts De ned to be lack of rainfall not high temperature 0 Cold deserts less than 20 C 68 F 0 Hot deserts gt35 C 95 F 0 Hottest recorded temperature Libya 58 C 136 F Typically less than 25 cm of rainfall per year 0 Alabama receives about 140 cm of rainfall per year Vegetation less than 15 of surface Cover about 25 of land surface Sahara Desert Africa is Earth s largest desert A region so arid that it contains no permanent streams except for those that m water in from elsewhere and has very sparse vegetation cover But before we continue Warm air can hold large amounts of moisture water As the air cools water vapor condenses and leaves the air as precipitation typically rainfall Cold air is relatively dry What causes air to cool 0 Forcing the air up to a higher elevation mountains 0 Contact with cold ocean currents 0 High latitudes poles less sunlight and cold oceans 5 Types of Deserts Subtropical 0 Warm moist air rises at tropics air cools as it rises and produces tropic rainfall dry air moves north and south at high altitude and cools air sinks around 2030 latitude and soaks up moisture as it warms up near the earths surface Rainshadow 0 Air picks up moisture from the ocean as the air moves up and over coastal mountains it cools and the moisture is released as rainfall Once over the mountain the dry air soaks up moisture Coastal near cold ocean currents 0 Cold ocean water cools air thus reducing the air s ability to hold moisture dry air blows onto land creating coastal desert Continental interior 0 For large continents air loses its moisture as rainfall and reaches the interior of the continent very dry e g Gobi Desert Polar o Caused by combination of atmospherically circulation delivering cold dry air and cold ocean water limiting moisture in air Weathering and Erosional process in deserts Physical weathering o Rocks may split along joints cracks Chemical weathering 0 Small amounts of moisture dew or rainfall seep into rocks and leach dissolve out certain elements which causes the rock to become brittle Desert Varnish A dark rustybrown coating of iron oxide and magnesium oxide that accumulates on the surface of the rock The exact cause is poorly understood but may involve microorganisms leaching out iron and magnesium from dust that coats moist rock to from Fe and Mg oxides Petroglyph 0 Drawings formed by chipping into the desert varnish of rocks to reveal the lighter rock beneath Lag deposit Weathering and Erosional processes in deserts Lag deposit 0 The coarse sediment left behind in a desert after wind erosion remover the c A lag deposit develops when wind bows away finer sediment leaving behind a layer of coarser grains FIGURE 178 l t i39 M t Vt lt39W PlMW39H 1quot 1Wquoti litl Time1 TimeZ ner sediment 7 Ventifact 39 I o A desert rock whose surface has been quot 39I faceted surface smoothed by wind 39 39 39 Facet 39 39 Did facet New39i ce abraSion the Windblow39i sano abrados the The wmd shifts mmcturm face of a 39ock fO39mIng a facet and a view facet towns De ation o The process of lowering the land surface by wind abrasion A ventifact from top Dry Valleys of Antarctica Desert Deposits Talus o A sloping apron of fallen rock along the base of a cliff I Caused by weathering and gravity falling rock simply piles up Alluvial fan 0 A gently sloping apron of sediment dropped by an ephemeral stream at the base of a mountain in arid or semiarid regions Playa o The at typically salty lake bed that remains when all the water evaporates in drier times forms in desert regions Salt Lake 0 A lake with high salinity due to high rates of evaporation and no outlets for the water forms in desert regions Sand dune o A relatively large ridge of sand built up by the current of wind Desert Landscapes Mesa 0 A large attopped hill with a surface area of several square kilometers in an arid region Cliff Scarp retreat o The change in the position of a cliff face caused by erosion Butte o A mediumsized attopped hill in an arid region Chimney 0 An isolated column of strata in an arid Cuesld region Cuesta 0 An asymmetrical ridge formed by tilted layers of rock with a steep cliff on one side cutting across the layers and a gentle slope on the other side the gentle slope is parallel to the layering Desert Pavement o A mosaiclike stone surface forming the Rewam ground in a desert layer Desert Problems ESQTS39SW 0 Deserti ca on a Asyu unelnc ndges called cuestas develoo whele strata ma legIOH o The process of transforming nondesert we quotOI mommaquot areas into desert I Process can occur within just a few decades I Caused by natural droughts over population over grazing careless agricultural practices and diversion of water supplies I Eg 1993 Dust Bowl in Midwestern US Caused by overpopulation in the midwest poor agricultural practices too much plowing and drought Many people lost farms and were displaced The timing was unfortunate as it occurred during the Great Depression
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