PHYSICAL GEOL FINAL EXAM STUDY GUIDE
PHYSICAL GEOL FINAL EXAM STUDY GUIDE Geol101
Popular in Physical Geology
verified elite notetaker
Popular in Geology
This 116 page Study Guide was uploaded by Shelby Green on Saturday April 23, 2016. The Study Guide belongs to Geol101 at Clemson University taught by Dr. Coulson in Spring 2016. Since its upload, it has received 109 views. For similar materials see Physical Geology in Geology at Clemson University.
Reviews for PHYSICAL GEOL FINAL EXAM STUDY GUIDE
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 04/23/16
Test 1 Study Guide Lecture 1 Geology is a course based off of science: Method of understanding things in this world Building using facts of something that is repetitively true Principles treated like facts today Not the only way of viewing the world of course (ex: philosophy) Scientific Method 1. Observation a. Ex: notice the spikes on the skeleton 2. Question a. Ex: why does the skeleton have spikes along its back? 3. Hypothesis: educated guess a. Ex: maybe the bones are a defense mechanism… if the bones of the spike are thin/weak, then it cannot be a defense mechanism Hypothesis Ground Rules 1. Testable: if a test/simulation cannot be made, the hypothesis is invalid 2. Predictive: guess the outcome of the test 3. Written as an “if-then” statement Can hypothesize on past/future events 1. don’t discard a hypotheses bc its too hard/easy 4. Data a. Collecting samples, measuring, etc 5. Evaluation a. Take data and evaluate against your hypothesis was your hypothesis right or wrong? Most of time will be wrong If wrong… 1. Eliminates one possible answer to the question 2. Use data to make new hypothesis 3. Repeat Theory A hypothesis with lots of data/people supporting it Strongly believed Law An elevated theory theory that’s been around a long time Sometimes exceptions Laws and Theories can be re-tested and revised Must have scientific data to challenge scientific ideas (beliefs invalid) o Ex: cannot use religious arguments to counteract What is Geology? The study of the earth (only a couple hundred years old) Earlier approaches to studying Geology Catastrophism: o Everything on earth formed very quickly because of 6 different catastrophes Uniformitarianism o Process in nature have always worked the same way in the past as they do today o Everything has formed by little changes adding up o Became a corner stone of geology in the 1800s James Hutton (Scotland): naturalist who spent years making observations about how processes work in the nature world Published his work in Theory of the Earth (1795) “The present is the key to understanding the past.” Actualism o Modified uniformitarianism Accounts for change of speed in some processes Includes that there has been catastrophic events that have helped modify the earth METEORITE FACTS They enter the atmosphere at up tot 40 km/s or 90,000 mph So a meteorite 30 m (100 ft) meteorite at 15 km/s would hit with a force of 4 million tons of TNT Meteor Crater, AZ ½ mile long and 600 ft across How did Earth form? 6 bya (billion years ago) there was no solar system, only a cloud of Hydrogen atoms called a Nebula 1. Nebular Hypothesis: a. Gravity still affecting hydrogen atoms in the nebula i. Hydrogen atoms attracted to each other slowly over time b. Solar disk model i. The cloud flattened out once hydrogen accumulated c. Protostar i. All the hydrogen accumulates into a circular shape (6 Ga) d. Fusion i. Needs to rise several million degrees Celsius Hydrogen is packed densely and the vibrational energies of the attracting H causes the temp to rise ii. The heat energy allows fusion to occur and it comes a star (our star) iii. Surrounding disk begins to cool 2. Forming the Planets a. Planetary accretion: i. Debris collides with each other; the masses will stick together to make a bigger object Asteroids meteors planets ii. Planetary accretion still happens 3. 4.5 Ga earth has reached a consistent size (starting age for planet earth) 4. Theia Impact a. Earth experienced a major collision with an other planet called Theia b. Probably a couple thousand miles of impact c. Earth gets reshaped through this massive collision 5. Theia Impact Aftermath a. The moon is debris that broke of from earth during the Theia impact i. The moon is moving away from the earth every year b. Molten planet i. The energy increase made the earth molten for a period of time ii. Allowed something weird to happen to earth… c. Density stratification i. Molten (liquid) separates like oil and water ii. Higher density stuff sunk to the center and the lower density rose up to the surface iii. Eventually, the molten period cooled and this explains the layers of the earth Lecture 2 Geology in the News: Satellite data is giving geologists new info about how and why the glaciers on Greenland are melting. Compositional Layers of the Earth 1. Crust (8-45 km) Light/low density elements (Si, Al, 2 ) Iron and stuff like that is a small percentage Types of Crust 1. Continental Crust: less dense (why continental crust tends to pile up higher) 2. Oceanic Crust: denser (why oceanic crust tends to be lower) 2. Mantle (45-2900 km below the surface) Denser elements More iron and nickel present 3. Outer Core: High iron and nickel concentration 4. Inner Core: Almost solid iron (aprox. 93% iron, 6% nickel, 1% other things) Physical Layers of the Earth (defined by physical/mechanical strength) ***Cannot use compositional layers and physical layers interchangeably a) Lithosphere: Much thicker than the crust, equals almost all the crust an the upper part of the mantel A brittle material, strong, will shatter if you apply enough force b) Asthenosphere: Not brittle, ductile/plastic material (like a melted chocolate bar) Low strength, give away easily c) Mesosphere (lower mantle) Deeper in the earth, so expected to be more ductile, right? Wrong. It behaves more brittle again for two reasons: o The amount of pressure that is being applied to this layer o The type of materials in it (stronger than the one above it) d) Core Outer Core: most ductile Inner Core: very brittle STUDY TIP: Brittle, ductile, brittle, ductile, brittle… (every other) Plate Tectonics Unifying theory of geology developed in the 1960s KEY to plate tectonics: The lithosphere is divided into pieces (plates) Those plates move around the surface of the earth o Like an ice burg (solid but drifts around the ocean) Map of the Plate The names of the plates don’t always match up with the corresponding continents/oceans how you would expect… (Not corresponding to major crust or oceanic boundaries) Some plates have both oceanic and continentals Antarctica: 90 Ma closer to the tip of Africa, lots of plants Today completely south, too cold/icy for plants How could this be? Developing Plate Tectonic Theory Alfred Wegener: Continental Drift o Popular scientist in the 1900s-1920s o He thought the shapes of the continents look like a puzzle and attempted to piece them together Data Supporting Continental Drift Mountain Belts: o Many mountain ranges match up (ex: Greenland and Europe’s mnt. ranges seem to pick up where they left off) Mesosaurs: o Little lizard that lived about 300 Ma o Found at the end tip of South America and the end tip of Africa Many people thought Wegener was crazy in his day b/c they didn’t understand how continents could move Mid Ocean Ridge (MOR): o World War II and Cold War: submarines needed navigation charts To put together these charts, scientists had to do extensive tests on the ocean floor Discovered the mysterious mid ocean ridge Mystery of the MOR Magnetic Anomalies Magnetic reversals: same on either side of the ridge The rocks on the sea floor contained little iron crystals that acted like magnets Age of the Seafloor The further the rocks were from the MOR, the older they were The closer the rocks were from the MOR, the newer they were Continental Drift Revised Seafloor spreading (1960s) The Midocean Ridge acts as a volcano all along the sea floor At some point in the past, the earth magnetic field was reversed and pointed south instead of north o The crystals must have been responsible As the sea floor spreads apart, the continents get spread apart o Wegner’s theory was proved How Do Plates Move Convection o Convection cells act like a pot on stove Ex: pot on stove warms water at the bottomdensity drops the water at the bottom risesthen it cools away from the heat sourcedensity risesdropsstarts over o BUT convection isn’t fast enough to account for all the motion New Hypotheses Ridge Push Model: new rock forming at the top of the mid ocean ridge, incline. As it new rock develops it pushes the existing rock/plate downhill and away a. Slab pull model: i. Plates get pulled back into trench ii. Once part of the plate enters the trench, the whole plate will get pulled down b. Slab Suction: i. Sucks down part of the asthenosphere (peanut butter consistency) slowly (Ex: like the titanic) Plate Tectonic Plates move slowly aprox. 10 cm/yr There are no ‘voids’ between plates What happens at the boundaries where 2 plates meet? **Boundary, margin, and edge are all synonymous 1) Pull away from each other 2) Run into each other 3) Slide past each other Divergent Margins 1. Mid-ocean ridge a. Oceancrust from oceancrust 2. Continent splits (rift valleys) a. Continental crust from continental crust b. Tend to have volcanoes on the ridges Ex) east part of Africa **STUDY HINT: rift valleys and mid-ocean ridges are types of plate boundaries/different types of divergent plate boundaries Convergent Margins 1. Subduction zone: ocean-continental collision a. Volcanic activity & big earthquakes i. Trying to push down a continental crust is like trying to push a cork underwater (Ex) Andes mountains (lots of volcanoes) why Chile and Argentina experience bad earthquakes 2. Collision zone a. Continental crust wont push down so they just push up i. Not volcanic ii. Some earthquake activity (Ex) Appalachian mountains **STUDY HINT: subduction zones and collision zones are types of pate boundaries/convergent boundaries Transform Margins 1. Plates slide past each other a. Neither plate is added to the boundary or destroyed (Ex) California Plate actions are all linked Lecture 3 Geology in the News Seismic activity in the pacific northwest linked to subduction of the Juan de Fuca plate beneath N. America o Volcanoes should form o Then, earthquakes occur Atoms: building blocks of all matter o Protons/neutrons make up nucleus Cannot change the # of protons for it to be the same element o Electrons rotate around the nucleus Can lose and gain electrons and still be the same element Atomic Number: the # of protons in the nucleus Element: # of protons tells you which element they belong to Chemistry of Earth’s Crust Most abundant element in the crust is oxygen. Silicon is second. STUDY HINT: FAMILIARIZE YOURSELF WITH THIS CHART What is a mineral? 1. Non-synthetic: form in nature 2. Inorganic: no fats/proteins/DNA (things you would find in living things) 3. Must be a solid 4. Set chemical composition/formula a. Some substitutions may occur: (Ex) if shortage of sodium, potassium can substitute in place of it 5. Crystalline: follows a specific crystal pattern Mineral Crystallin Properties Not 1. e Color: Crystalline some minerals are always the same color a. But many minerals have a large range of All the same mineral colors 2. Streak: tells the color of the mineral if it was ground up into powder form a. Rub mineral across ceramic tile (most often the same color as the tile) Black mineral but reddish streak 3. Hardness: how tough the mineral is a. Moh’s scale: 1-10, 10=hardest Tools: ~Hardness <2.5 if your nail can scratch mineral ~Pocket knife = 5 hardness 4. Luster: how shiny a. Vitreous: glass-like b. Silky: soft/florescent glow c. Resinous: looks like its covered in tree sap 5. Effervescence: bubble and fizz a. Some when exposed to weak acid will start to dissolve (ex: HCl + CaCO = CO + Ca + OH + Cl) 3 2 6. Crystal Form: shape the mineral should have is there is crystal formation a. if minerals grow in its ideal conditions crystals (ex) big crystal in pic grown in ideal conditions base in pic not ideal conditions 7. Breakage patterns: how the mineral will break a. Fracture: irregular patter for a break b. Cleavage: breaks along very flat smooth surfaces (cleavage planes) i. Defined by number of planes/angel the planes meet Ex) Hyalite Minerals grouped by common anion Anion is a negatively charged particle (left side of the periodic table) Many groups exist… o NOTE: Minerals can be classified by common anion Mineral Groups: Sulfides (S): a single atom as an anion o ______ + sulfur = mineral Oxides (O): a single atom as an anion o ______ + oxygen = mineral If you have ______ + oxygen, take away the oxygen and you’re left with the _______ . The harder the _____ is to extract from the anion, the more expensive the process is o Ex: why diamonds are so expensive Sulfates (SO 4: used as an anion o Common on the surface of the earth Construction ex) dry wall Medical Industry ex) plaster for casts Phosphates (PO ):4used as an anion o Not as common on the surface of the earth Fertilizer Bones and teeth (Ex: broken arm how tot get phosphate crystals to grow back together nice and strong) Carbonate (CO ):3anion o effervescence o Invertebrate organisms often form shells out of carbonate Ex) plankton o When organism dies, the shell remains, builds up over time, and becomes really thick Coral reefs Silicates (SiO4) : anion o Bond together in a particular pattern o Tetrahedron Easy to form o Polymerization: take the little tetrahedra and bond them to one another o 2 tetrahedra never share more than 1 oxygen atom between them Types of Silicates : Sub-groups depend on how tetrahedra polymerize 1. Island silicates: a. they don’t polymerize, bond to positively charged cations instead 2. Chain Silicates: a. Tetrahedras combine to make a long chain b. Single chains and double chain have different properties 3. Sheet Silicates: a. Sheet like (covers an entire flat 2D surface) 1 layer of tetrahedra 1 layer of positively charged ions 1 layer of tetrahedra **easy to peal back layers 4. Framework Silicates a. 3D network b. The most common for mineral at the surface (Ex) quarts The Rock Cycle Rocks and minerals are not the same Rocks: one or more minerals stuck together and “maybe some other nature stuff too” Only Three Types of Rock **Differentiated based on how they form linked by rock cycle Magma: liquid rock will convert to solid when temp cools when magma cools and crystals form together to make a solid Igneous Rock forms Weathering: rock breaks down by surface processes Erosion: a transport Deposition: when the sediment settles after erosion Lithification: turned into stone Sedimentary rock is formed Metamorphism: rock changes form b/c temp/pressure increases as build up occurs many minerals don’t react well at high temps/pressures so they’re forced to change into metamorphic rock Continue increasing the temp to the melting point of the minerals, and they will return back to magma cycle starts all over again Lecture 4 Geology in the News 21000 homes in Flint, Michigan have lead contamination in their drinking water Magma: Why do we care? Plan ahead for eruptions: good to know when it will erupt/how big the eruption will be/etc Good to understand the material for construction/ornamental uses What is magma? Magma: liquid rock below ground Lava: liquid rock on the surface Types of Melting Processes 1. Partial melting: a. rock don’t melt at one set temp, but rather a large range of temps b/c the different minerals in the rock all have different melting points 2. Wet Melting: the presence of water will lower the melting point of the rock a. Needs to be saturated (water inside/out of the rock) b. Water destabilizes the minerals in the rock and cause them to start melting faster 3. Decompression Melting: a. The less pressure you have, the lower the melting point will be i. The closer to the surface of he earth, the easier the rock will melt ii. That’s why high altitudes have lower boiling/melting points Magma Composition Gases: dissolved gas mixed into the magma SiO 2 silicon content is used to classify magma o Magma in different places on earth have very different properties Three main types 1. Basaltic magma a. Source comes from within the mantle and works its way to the surface b. Called Dry magma: low water content c. SiO 2ontent: 50% SiO 2 d. Temp will exceed 1100°C hottest of the magma types e. Low viscosity **convert C F 2. Andesitic magma a. Andesite Line aka Ring of Fire b. Originates from the mantle i. Found only in a few places on earth ii. Raps the edges of the pacific ocean (not including Hawaii) c. Comes from subduction zones: as the crust gets subducted, the crust starts to melt and the magma from the melted crust begins to pass back up through other plates to reach the surface (how other minerals get mixed in that classify it as andesitic) d. Name came from Andes mountains e. Moderate viscosity f. 60% SiO ,2a little higher water content, cooler temp (900-1000 °C) 3. Rhyolitic Magma a. Cool temp: 700-800°C b. Originates in the crust (a more shallow depth than the others) c. Only found in continental crust d. About 70% SiO 2 e. High viscosity, silicate chain molecules f. Called Wet Magma b/c higher water content STUDY HINT: magma with Plagioclase + liquid higher water content means its closer to the earth’s surface and as temp increases, % of SiO2decreases Freezing of Magma Crystallization: o Freezing/making crystals in the process Partial freezing: o As magma is being crystalized, each mineral will be formed at a specific temp Plagioclase: o Crystals that form before the rest of the liquid Fractional Crystallization: o The rock at the end has a different composition than the original magma b/c something was removed during the process Ex: splitting up the red and green M&M’s Equilibrium crystallization: o The magma you start out with is the same composition as the rock you end up with Ex: same # of red and green M&M’s that you started with Bowens Reaction Series: Minerals form/crystalize in a specific order as they cool Ultramafic Mafic Intermediate Felsic Discontinuous Branch: As the temp decreases, that mineral cannot form at its ideal temp anymore so it is discontinued and changed to the next mineral o 1400°C = Olivine 1400°C gets lowered Olivine changes to Pyroxene Continuous Branch: Some minerals can form over a large range of temps o Plagioclase: calcium replaces sodium as temp cools Higher temp, higher calcium % Lower temp, lower calcium % *** Discontinuous branch continues at intermediate phase where sodium-rich plagioclase and Biotite will both turn into orthoclase Igneous Rocks Two Broad Types: 1. Plutonic (aka Intrusive): forms below the ground, magma never surfaces before it cools 2. Volcanic (aka Extrusive): formed after eruption and cools on surface of the earth Two Properties needed for ID: 1. Texture a. Measure crystals formed on surface 2. Composition a. What minerals are in my rock? Plutonic Rocks Plutons: large mass of plutonic rock o Many types of plutons differentiated by the size and shape Pluton Types: 1. Dikes and Sills: skinny but long a. Dikes: cut vertically through the rock b. Sills: cut horizontally through the rock (like a window sill) 2. Laccolith: a. dome shaped b/c magma has worked its way to the surface but gets stuck 3. Batholith: huge size/not distinct shape a. Mount Rushmore is an example of a batholith (small by batholith standards) Textures of Intrusive (Plutonic) Rocks Pegmatite (pegmatite): large crystals (>1cm in diameter) Phaneritic: small but noticeable crystals (< 1cm in diameter) Composition Felsic: light colored minerals o White, off white, pink, and red o High SiO 2 Intermediate: Grey o Balance between dark/light colored minerals o Moderate SiO 2 Mafic: dark o Black and brown o Lower SiO 2 Ultramafic: green or yellow o Lowest SiO 2 **Color index (how light/dark is the rock) works 9 out 10 times Textures of Extrusive (Volcanic) Rocks Porphyritic: mix of little and big grains o Phenocrysts: big grains (formed below surface), and the rest of the formed above ground o Looks like a chocolate chip cookie Aphanitic: crystals are too small to see Glassy: the rock looks glassy o Color index will fail: this is actually felsic o Looks smooth or has fragments of smooth within it Vesicular: tiny little opening formed from areas where gas used to be trapped during its magma stage o Sponge-like/honeycomb like Geology in the News Volcanic glass ‘egg’ found after Kilauea erupted last week Volcanoes o “The US doesn’t have to worry about volcanoes…” FALSE o Japan and Indonesia are the only countries with more volcanoes than the US o Active United States Volcanoes: o Hawaii = 7 o Alaska = 41 o Contiguous 48 states =20 Case Study Krakatoa o Indonesian Island Volcano o Eruption in Aug 26, 1883 o 200 millions tons TNT = 13000x the yield of the Hiroshima A-bomb 3 o 25 km of ejecta o heard >3000 miles away o Air pressure waves circled the globe for 5 days, caused waves in the English channel o Over 30,000 dead, several languages went extinct 2/3 of island destroyed, new volcano built up since Explosiveness Volcano Explosively Index Viscosity: the resistance to flow Water low viscosity Peanut butter high viscosity Controlled by 2 main things: 1. Temp: a. The higher the temp, the lower the viscosity 2. Silica content: a. The higher the silica %, the higher the viscosity Magma Properties: Viscosity controls gas content High viscosity… o Gas can’t work it’s way up to the surface o Gas pressure builds up o More of an eruption Low Viscosity… o Gas can easily work its way to the surface o Not an explosive eruption Non-Explosive features Pahoehoe o Early stage of cooling o The surface of the lava starts to crust over, but the lava continues to flow underneath that crust Squishy/spaghetti like appearance Aa o More advanced cooling stage (weeks later) o More brittle, looses its squishy/spaghetti appearance Vesicles o Where gas escaped, leaving holes in the rock Explosive Features Lahar o A mud flow associated with volcanic eruptions o Can happen several days into an eruption o Ground temp rises as lava comes to surface melts snow/ice fast moving mudslides Can occur before actual eruption Ex: Mount Saint Helen Pyroclasts 1. Bombs o Larger solid particles ejected during eruptions o >64 mm 2. Lapilli o Smaller solid particles that get ejected during eruptions o 64-2 mm 3. Ash o Smallest debris (different that ash from a fire) o < 2 mm Massive amounts can burry cars If gets sucked into engine, tears up engine **Why there are no fly zones over volcanoes Health hazard: acts like cement if ingested 4. Pyroclastic Flow o Less dense than earth’s atmosphere so when it looses its momentum, falls back down to the earth o B/c its gas, moves very quickly o Cannot out run and hot enough to kill o Can occur before eruption begins Volcano Types o Shield volcano o Profile looks like a shieal broad face/low slow shield o Basaltic magma o Low viscosity gradual build up, hence the low slope o Tephra (cinder) cone volcano: o Steeper, cone shaped, but decently small o Don’t get particularly big b/c they’re not the primary volcano (usually at the base of another tephra lager volcano) o Most erupts with pyroclastic material o Stratocone (composite)/stratovolcanoes o Class “Hollywood” volcano o Greater/powerful explosions o Viscous magma Stratocone Magma flow not very far tend to be taller Supervolcanic Eruptions Not a type of volcano, but a type of eruption o Eruption big enough to affect global climate 3 Tambora eruption (1815) 100 km ejecta o Changed temp in Ireland, cold summer so crops didn’t grow o Frost in NY on the 4 of July 3 Yellowstone Huckleberry Ridge eruption (2 Ma) 2500 km eject o 75000 years ago something happened to cut the human gene pool in half o Scientist believe its due to this supervolcanic eruption Volcanoes don’t just exist at subduction zones Hot Spots also develop volcanoes explains Hawaii Plate sits on top of hot spot and volcano forms Plate will shift and the volcano will shift with plate That volcano becomes inactive A new volcano will form over top of that hot spot Study Guide Test 2 Lecture 5 Sediment: most common type of rock Sedimentary Processes 1. Weathering a. Parent rock breaks down into particles called sediment Two types of weathering: a. Physical Plant roots: split rock as the plant grows Frost wedging: water gets into crack freezes ice expands splits rock repeat b. Chemical More common (ex) feldspar +H2O+H2CO3 kaolinite + dissolved ions Saprolite Formation: substance that has undergone extensive chemical weathering (translates to “rotten rock” because it falls apart easily) 2. Erosion a. Requires energy to transport from A to B (ex: water, wind, glaciers, gravity like landslides) 3. Deposition a. Basin: any place that can be filled with sediment b. Accommodation space: measurement of how much sediment can fit in a basin c. Subsidence: when the ground level in a basin sinks downward because of weight from sediment thus creating room up top for more sediment 4. Lithification a. Compaction: sediment gets compact as layers are added to basin **Layers also referred to as strata or beds b. Compaction fills the caps between the stratum of sediment c. Cementation: when the constant compaction pushes absorbed water out of the sediment layers and leaves behind little crystals that act as natural cement Classification 1. Detrital (aka clastic) sediment created by physical weathering a. Gravel b. Sand c. Silt d. Clay Poorly sorted Traits of Detrital Material Sorting: how uniform the grain size is indicates how long the erosion process was o Long erosion = well sorted (close to same size) o Short erosion =poorly sorted (all different sizes) Rounding: how round the grain is indicates how long the erosion process was o Long erosion = well rounded o Short erosion = jagged, poorly rounded Identifying Clastic Sedimentary Rocks Well Grain size is key pick out the dominate grain rounded size o Ex: sand = sandstone o Ex: silt = siltstone 2. Chemical Sediments a. Form via chemical reactions Dissolution and re-precipitation Saltwater evaporation b. Crystal structures c. Usually comprised of 1 major mineral type: Ex: halite = salt rock Ex: quartz = chert d. Economically viable: high concentration of one mineral so easy to find if looking for that specific mineral without the processing costs 3. Biogenic Sediments: a. Sediment particles come from living organisms (ex: shells, partially decayed plants, microscopic organisms) i. Chalk: poorly cemented ii. Limestone: well cemented, tiny shell fragments iii. Coal: compressed plant material Mass Wasting (landslides) Slope Destabilization Factors Angle of repose: max avg. number of steepness before whatever is added to the top just falls back down Lack of Moisture: low water content/dry Excessive moisture: too much moisture turns sediment into mud with landslides easily Lack of vegetation: plant roots stabilize slopes and hold sediment in place Excessive vegetation: too much vegetation can (1) add too much mass to a steep slope, (2) absorb too much water and make soil dry, (3) roots make channels for water to travel down Types of Mass Wasting/Landslides Categories based on: o Material: sediment or mud or rock or snow or ice o Type of movement: rolling/sliding/flowing/falling downhill o Speed: rapidly or gradually 1. Rockslides: a. Fast, but not as fast as other materials b/c of friction between the ground and the rock 2. Creep: a. Sediment moving slowly downhill b. Barely noticeable Ex: fence on hill starts to lean downward because sediment is moving downhill Causes of Mass Wasting Thunderstorms/heavy rains Earthquakes Human Landscaping Clear cutting **Risk Management Maps are updated frequently to determine how at risk certain areas are for mass wasting Preventing Mass wasting Drainage control: adding pipe systems to prevent over saturation of ground Decrease slope grades: flattening hills to decrease the speed of run off Building codes: like not allowing big houses to be build in steep hills Retaining walls : concrete barriers to block falling rock from reaching roads Rock Bolts: drive bold through rock into rock behind it to hold the outside rock in place **Prevention Cost: expensive to build/implement changes, but damage is more costly estimated return is $10-$2,000 per $1 spent on prevention **Case Study 1983 slide caused $200 million in damage, but could have been preventable if $0.5 million had been spent on drainage systems Lecture 6 Metamorphism (very slow process) Metamorphic rocks help understand the geographic history of an area Temperature Geothermal gradient: how fast the temp go up with depth in the earth (varies) Avg: changes 30°C/km Typical range: 20-60°C/km Metamorphism via Heat Contact metamorphism: rock undergoes metamorphism due to direct heat from magma coming towards the surface o Primarily temp driven o Limited in scope/only occurs close to magma Pressure ** Note: 1 bar= 1 atm at surface of the earth Pressure gradient: ~300 bar/km depth Types of Pressure 1. Confining pressure: rock is feeling equal pressure from all directions a. (Ex) swimming underwater 2. Directed pressure (aka differential): the majority of the pressure is being applied in a specific direction a. Compressional How much pressure is needed? Most metamorphic rocks from at 10- 30 km (aprox. 1- 1.6 mi) depth (mid-lower crust) Exposure How metamorphic rocks get back to the surface o Faults rocks on either side of fault move/broken down thorough weathering and erosion Types of Metamorphism Via Pressure o Regional metamorphism: large scale process/opposite of contact metamorphism o Contact metamorphism: INSERT DEFINITION o Fault metamorphism: occurs on a small scale along the fault line. Pressure is still the primary driver Via Fluid o Metasomatism: rock comes in contact with very hot ground water. Water flushes things out of the rock or deposits new minerals that change the mineralogy Ores: high concentration of a specific mineral o Seafloor metamorphism: almost always forms basalt. specialized in environment where the cold seawater interacts with the rock Metamorphic Change Metamorphic grade: measures metamorphic change due to change in temp and pressure o Low, intermediate, high o Doesn't tell you anything specific/needs to be better differentiated Index minerals: a mineral can help identify the correct metamorphic grade o Each index mineral is formed in very specific environment Metamorphic Facies: group of index minerals that form at the same temp and pressure o Ex) blueschists facies includes the minerals glaucophane, lawsonite, epidote 7 Major Metamorphic Facies **Facies used to reconstruct how metamorphism occurred Length of Metamorphism Prograde: temp and pressure are climbing towards peak or metamorphic grade in rock history Retrograde: temp and pressure are decreasing after they have already peaked in rock history (usually due to reaching the surface) ** We need to figure out the time frame of each period Changes within minerals can record Pressure-Temp changes o Un-uniformity allows for tracking o Crystal grows outward with rings like a tree trunk Types of Metamorphic Rocks 1. Foliated Metamorphic Rocks a. Slate b. Schists: hard to identify (samples can vary drastically) c. Gneiss (pronounced “nice”) *these rocks are formed from different pressures 2. Non-foliated: a. large crystals b. high concentration of one specific mineral c. appearance is very similar so you cannot eyeball the identify i. Hornfels ii. Quartzite iii. Marble Geology in the News: sudden volcanic eruptions found to trigger from gas bubbles in magma Structural Geology: Focuses on how rocks deformed after they've been created = rock deformation Note: Topographic (landscape) features and geologic structures are very different Tectonic Forces 1. Tensional: stretching an object (pulling away from the center in two directions) 2. Compressional: the area is getting squeezed or compacted 3. Shearing: material getting slid in two different directions at the same time Responses to stress: Brittle: break with enough force Ductile (aka plastic): bend away from force Response can vary based on: o Rock type, temp/pressure, speed of deformation (faster the application, the more brittle the response) Types of Structures Folds: formed with a ductile response to a compression force *Know limbs and hinge (where all the motion seems to be occurring) Classifying Folds 1. Shape (in road cut or cross-section view) a. Antiform: anti-smilie face (frownie Anti face) b. Synform: smilie face Syn c. Overturned: i. Overturned Antiform ii. Overturned Synform iii. Overturned can’t tell if Antiform or Synform Overturned synform Overturne d antiform Overturned 2. Age of Layers relative to each other a. Anticline: oldest layer in the center fold between the limbs b. Syncline: the center fold layer is the youngest rock **This happens because tectonic forces can cause an entire stack of layers to get turned upside down 3. Geometry: a. Horizontal: squeezed in from both sides and nothing else (looks horizontal in birds eye view) b. Plunging: squeeze from both sides and tipped up or down (more common) Synform, Syncline, Antiform, Horizont Anticline, Types of Structures Plunging al Joints: brittle response o Most common type of geologic structure o Tend to occur in sets o Can have more than one joint set within rock body Faults: brittle response of cracking and then move/shift in different directions o Different sizes: from a couple of inches to 100s of miles o Classified by slip direction Types of Faults: 1. Dip Slip Fault: inclined fault plane, vertical motion, one side up and one side down **Picture yourself walking down the fault line the side your feet would touch = foot wall a. Normal Dip Slip: when the hanging wall is lower, and the footwall is higher b. Reverse Dip Slip: when the foot wall is lower, and the hanging wall is higher Reverse Normal Reverse c. Thrust Fault: hanging wall higher than foot wall (not a steep incline, occur at subduction zones) 2. Strike-Slip Faults: horizontal movement (parallel to the fault plane) a. Left-lateral: no hanging/foot wall, each side thinks the other Top layer has slid up moved to the left on top of bottom layer b. Right lateral: each side thinks the other side moved to the right Faults and Forces Compressional: hanging wall slides up line Tensional: hanging wall slides down line Shearing force: hanging wall moves to side Lecture 7 Geology in the news: 6.4 magnitude earthquake in Southern Taiwan Apartment building fell over Several dead and 100 missing Chinese new year celebrations cancelled Earthquakes: build up of energy along a fault or plate margin 1. Stress < Friction 2. Stress ~ Friction (energy has built up, but still no movement, elastic deformation=rock starts to bend) 3. Stress > Friction (plates move) Earthquake Frequency Small earthquakes are quite common o Aprox. 1 million quakes with a magnitude of 2 per year ~ 2,740 per day o Only about 10 quakes with a magnitude of 7per year Earthquake Movement Focus: underground point where the movement occurs on the fault in the earthquake o The center fault may not move o Many foci are only 2-20 km deep in continental crust (usually not any deeper b/c the rock has to be brittle for earthquakes to occur) Epicenter: geographic point on the surface of the earth directly about the focus Foreshocks: small movement that occurs before earthquake to try to relieve some of the built of energy Aftershocks: small movements that relief the rest of the energy after earthquake Seismic Waves Seismic waves: waves which the energy of an earthquake moves away from focus Three Types 1. Primary Waves (P waves): push/pull or compressional waves, fastest wave (6 km/s, 20x faster than the speed of sound), can move through both solids and liquids a. Ex) moves like a slinky or like a caterpillar 2. Secondary Waves (S waves): shear waves, vertical motion, slower (about half the speed of p waves), cannot move through liquid a. S wave shadow zone: area where s waves can’t get to (where the red lines don't reach in diagram) 3. Long Surface Waves (L waves): vertical and lateral motion, restricted to the surface of the earth Measurement and Detection Seismometer (aka seismograph, the outdated name): tool to detect earthquakes Three myths about seismometer: 1. It’s a solo machine: acutally needs 3 seismometers minimum (one calibrated for E/W, one calibrated for N/S, one calibrated for Up/Down or z axis) 2. Old fashioned looking machines in movies: those are outdated everything is done digitally now 3. Swinging needles: the pendulum used for drawing waves doesn’t actually move, but the machine itself does (pendulum isn’t used anymore, everything digital) Finding the focus: P waves arrive , then S waves arrive *Understand how this chart is used Measuring Damage 1. Mercalli Index: scale that measures how much damage/destruction the earthquake caused a. Uses roman numerals (I=lowest grade of damage) b. Not used by scientists b/c doesn't account for how populated the area hit was c. Easier to manipulate for insurance companies 2. Richter scale: measures the amount of shaking (Charles Richter 1935), logarithmic scale a. Not typically used by scientists 3. Moment magnitude: the amount of slip that occurs on the fault a. Easier to calculate b. Can be measured based on field data c. Best for scientific use Quakes and Plates Faults are along plate boundaries o So, earthquakes occur near plate boundaries o Deep earthquakes occur along subduction zones Because of this trend risk assessment maps are made *Some quakes can still occur far from plate margins But predicting earthquakes is difficult because every fault is different o Diff rocks/plate motion/forces o No magic formula to calculate when an earthquake will occur Damage Control Land Use Policies: o Ex) 1972 California Law made it illegal to build on the fault Building Codes: o Make sure buildings are stable so there is less damage Ex) Tall buildings can’t be built along fault lines Site Selection: o Solid rock is best to build on b/c of stability Liquefaction: o Loose sediment contains a lot of water, when seismic waves goes through the sediment, it creates mud Earthquake myth: o Rocks will crack open and swallow your entire house Lecture 8 Geology in the news: tin cans found within the walls of collapsed buildings after Taiwan earthquake Dating Methods st nd Relatird dating: putting together a sequence to know what came 1 , 2 , and 3 o Ex) Dinosaurs existed before humans o Cost effective/essentially free/easier Absolute dating: putting numbers on actual events o Ex) dinosaurs went extinct x million years ago o Can be expensive/more difficult/not always important Relative Dating Fossils: any evidence of past life forms o Footprint, plant impression, sea shell, etc o Mainly found in sedimentary rock Stratigraphy: subset of geology (predates) study of strata or layers of rocks Unconformities: breaks or gaps in time records where not all the time periods are represented in the layers of rocks (example on right) o Gap occurs when… Sediment deposits runs out or no other layers are formed during that time Run out of accommodation space (basin becomes full) Eroding sediment faster than it is being deposited Three types of Unconformities 1. Disconformity: sedimentary rock on one side of gap and a diff type of sedimentary rock on the other (black line=gap) 2. Nonconformity: sedimentary rock on one side of the gap and igneous or metamorphic on the other **study tip: nonconformity = not the same 3. Angular unconformity: layers underneath gap come up and strike gap at an angle (takes a long time to develop) Two Problems with Unconformities 1. Identification: hard to find the gap 2. Duration: hard to find out how much time is past Stratigraphic Principles 1. Principle of Original Horizontality: layers of sediment originally form as a horizontal line 2. Principle of Superposition: when looking at a stack of layers, the one on the bottom is the oldest and layers above get younger 3. Principle of Cross-Cutting Relationship: whatever did the cutting is the youngest 4. Principle of Faunal Succession: fossils seen in different layers are always going to occur in a set pattern (the oldest rocks contain oldest fossils) a. Correlation: linking two places together to see how old the rocks are in relation to one another Example: correlation found via faunal succession Correlation with Fossils Not all fossils are great for correlation o Want to identify short spans of time (more precision=stronger correlation) o Smaller, inconspicuous fossils usually better Index (or guide) fossils: ideal fossil to use for correlation Four Qualifications to be index fossil: 1. Were numerous: a. a lot of them don’t get fossilized, so a bigger population increases chances of fossils 2. Widespread: a. The more places it lives in, the more places that can be correlated together 3. Went extinct quickly: a. “Die as fast as you can.” b. Precision = stronger correlation (cockroaches are a bad index fossil b/c they’ve been around forever) 4. Easy to identify: to insure you’re comparing the same fossils Other Correlation Tools: Some places don’t have index fossils to use, so there are other dating methods Lithostratigraphy: correlations based on rock types o Decent at starting correlation but too many underlying factors to finalize correlation Sequence Stratigraphy: correlation based on pattern/sequence of unconformities o Beneficial to oil and gas industry b/c costal areas are ideal for sequence stratigraphy Chemostratigraphy: chemically correlate areas o Ex) Iridium anomaly at the Cretaceous-Tertiary boundary: meters and asteroids have a massive amount of iridium so there must be a connection there Magnetostratigraphy: magnetic signature that get recorded in rock layers o A little rough on the eyes: like trying to take two bar codes and slide them around until you can find matching black and white stripes Geologic Time Scale Originally built via stratigraphy Fossils were the key for defining boundaries Eons st 1. Hadean: 1 billion years of the earths existence a. 4.5 Ga-4.0 Ga b. Density stratification period c. Earth’s earliest atmospheres/oceans form 2. Archean: continent building a. 4 Ga – 2.5 Ga (about ½ billion years long) 3. Proterozoic: oxygen build up in the atmosphere for the first time a. 2.5 Ga - 550 Ma 4. Phanerozoic: curretnt eon we’re living in where Fossil records are at its best Three Phanerozoic Eras 1. Paleozoic (550-200 Ma): translates to “ancient life” a. Cambrian Explosion: a sudden burst of new organisms on the scene 2. Mesozoic (200 Ma – 65 Ma): dinosaurs 3. Cenozoic (65 Ma – now): includes the ice age a. Mammoths became dominate species Geology in the News: new info on why quake occur deep in subduction zones water released from mineral called lawsonite reduces friction and enables the fault to move despite the high pressure environment Absolute Aging Two Approaches: 1. Non-radiometric: involve zero radiation 2. Radiometric: involve radioactive materials Non-radiometric Methods 1. Varves: type of sediment deposits a. Thin layers that alternate light and dark bands that only form under certain conditions (counting bands tells how long the climate in the area has met the proper conditions) i. Light color normal sediment deposits during warmer months ii. Dark color when lake ices over and additional sediment not added to water, but sediment floating in water settles and gets deposited ***Note: Varves only form if nothing disturbs the sediment (crabs, snails, creatures of that nature) 2. Dendrochronology: a. Counting the growth ring in trees (1 ring = yr, dark rings= tree had stopped growing) i. Note: some species of trees don't form rings yearly (some more than one ring per year or some less than one ring per year) ii. Forest fires can stop the trees from growing b. Used to learn about area and its environment i. Climate can affect if the tree grows quickly or slowly ii. Cross Reference trees with each other to get an extended time lie Radiometric Dating Isotopes: atoms of exact same element with different number of neutrons present o Radioactive isotopes: neutrons that are weighed unstable Radioactive Decay: radioactive atoms will break down to become more stable o Parent Isotope: before decay o Daughter Isotope: after decay (***can have multiple daughter isotopes) ***Note: there is no way to predict when an atom will start decaying, but the rate of decay is known so once decay starts, can predict when the process will end. Radiation: emitted energy Decay Series (aka chain): multiple steps/daughters of decay to become stable Half-life: the time it takes for half the current atoms to decay (# of parents divided by 2) Half-lives don't vary with any environment factor. o Th-234 = 24.1 days o Pb-210 = 22.3 years o U-238 = 4.4 billion years Radiometric techniques are created/improved by first dating things that we already know the age of (ex: Egyptian mummies) Requirements for Radiometric Dating: 1. Radioactive isotopes must be present in the specimen 2. Must have both parent and daughter atoms in specimen a. If only parent atoms decay hasn't started b. If only daughter atoms decay is already finished 3. Can only go so far back in time a. Usually can go max 5 isotopes back until parents atoms eventually runs out 4. Closed System: not interactive with its surroundings a. No parents or daughter isotopes to be added or subtracted i. Add parents/lose daughters: looks like little time has passed ii. Add daughters/lose parents: looks like more time has passed Case Study of Carbon 14 C-14 N-14 + particle + energy (carbon 14 decays to nitrogen 14) Half life of C14 = 5,730 years o Can track back to 10 half-lives o Extremely sensitive Earth hasn't run out of C-14 because this reaction… o Cosmogenic ray + n + 0 14N 14C + p + o C-14 globally distributed because atmospheric reaction all around the world o Amount decaying = amount produced Some isotopes do go extinct because they’re not reproduced Carbon Dating Carbon dating can only go back so many year and can only work for certain materials (doesn't work for rocks/minerals) o Animals are exposed 14 C-14 through the food chain 14 C14 + O2 = CO2 in atmosphere, plant filters the CO2, the animal eats the plant, and from there after, everything in the food chain is exposed to C14 When the animal dies, it becomes a closed system because no parent atoms added by eating Some organisms don't get carbons from the atmosphere or food chain Decay Equation Age = [ln(N /N )/-0.693]*half-life f 0 14 o N fN 0 % C in the sample relative to amount found in living tissue (i.e., how much parent is left) Ex: fossil still has 10% of its4C Age = [ln(0.10) / -0.693) * 5,730 Age = 18,940 years old Assumptions for Carbone-14 1. System remains closed after death a. Not true extra tests are required to ensure specimen was a closed system 2. Amount of C-14 in living tissue doesn't vary through time a. Not true… i. C-14 production varies based on solar cycles but variations are small/on short timescales ii. Fossil fuel burning changes the amount of C-14 in the atmosphere (scientists already took into account this change and fixed their methods) TEST 3 STUDY GUIDE 2/23/16 Geology Lecture 9a Climatology Intro to Climatology • Why do we care? • Climate change. If conditions are changing on earth, it may affect where we live, how much food and water are available, how severe natural hazards are, etc. • Why are we covering this in a geology class? • Geologists do a lot of climate research! Studying ancient climate helps predict future climate trends (remember uniformitarianism) Climate Basics • Climate: Average surface conditions over some long period of time – Ex: usually want at least a decade of data • Often confused with Weather- Average surface conditions over some short period of time – Ex: days-season – Ex: Temp in Clemson last February was often in the 30s, but that is not Clemson’s climate; that was just the weather during Feb 2015 • Why does climate vary so much around earth? i.e., why don’t we have a desert planet or an ice planet like in Star Wars? – Climate (cli) is determined by complex interactions among the lithosphere, atmosphere, biologic processes, ocean circulation, etc – It’s not just about atmospheric processes! System Interactions • Interactions among all these earth systems are complicated to untangle – Ex: how do the lithosphere and atmosphere interact to affect climate? • Some interactions create feedbacks- a change in one component of system affects other things that then eventua
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'