Geology Study Guide

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Geology

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Dec 6, 2023

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The exam may consist of multiple choice and short-answer questions, and will be about 32 questions total. The following list of questions should help you prepare for the exam. Please include in your studies not only materials from the lecture and text, but also from poll everywhere questions and in-class activities (both graded and ungraded). Volcanoes and Hot Spots ● Explain how pressure and temperature correlate with phase changes, and describe how magma composition impacts melting temperature ○ Where would the line for a felsic rock be on a temperature/pressure phase diagram? ○ Does a wet magma melt at a higher or lower temperature than a dry magma? Viscosity is the resistance to flow. ● If something is low in viscosity it flows quickly. If something is high in viscosity it is slow. ○ The colder something is, the more viscous it is. The hotter it is, the less viscous. ○ Therefore, high temps=low viscosity=flowing faster=covering more areas. Low temps=high viscosity=slower=smaller impact area. ○ ● Magma works its way up through pipes in the Earth. As it rises it cools and solidifies/becoming more vicious. ○ Mantle rock is the lowest in viscosity. ○ Magma that forms within the Earth’s crust is plutonic igneous. ● Where magma forms affects its qualities. A huge factor is the amount of silica content. More silica=more viscous. Less silica=less viscous. ○ Furthermore, high silica materials have a lower melting point meaning that higher silica will melt faster. ● Another factor is volcanic eruptions. Higher viscosity means more gasses trapped which leads to more explosive eruptions. Stratovolcanoes are more likely to explode because the magma is more viscous than in shield volcanoes. ● Three types of magma: basaltic, andesitic, and rhyolitic ○ Viscosity from lowest to highest: basaltic, andesitic, rhyolitic. BAR: the bar is low. ○ Basaltic: Lowest silica, highest temperature, lowest viscosity, divergent, decompression melting ○ Andesitic: Medium silica, medium temp, and medium viscosity, convergent, melting due to the addition of water. ○ Rhyolitic: Highest silica, lowest temp, highest viscosity, magma comes from continental crust ○ Basaltic and Andesitic find their origins in mantle rock. ● Ultimately: ○ Low silica=high temperatures=low viscosity=flowing faster=milder eruptions=higher melting points=mafic oceanic magma=divergent boundary=basaltic=shield volcano=mantle melting=creates flood basalts. Dark-colored rocks. ○ High silica=low temperatures=high viscosity=flowing slower=violent eruptions=lower melting points=felsic continental magma=convergent boundary=rhyolitic=composite volcano and stratovolcanoes=lithosphere/crustal melting=high water content=creates

calderas and pyroclastic flows. Light-colored rocks. Magma Origins ● Most volcanoes are located at subduction zones although they may also be at hot spots and divergent boundaries. ● Subduction zone/convergent boundaries: Water is expelled or driven from subduction plates lowering the melting point and causing partial melting. ○ Basaltic rock that rises may mix with creating an intermediate silica content. Increased silica. As a result volcanoes on plates overlying subduction zones. ○ Heat from the rising magma from the mantle melts lower continental crust to form rhyolite. Rhyolite is formed by partial melting of the continental crust due to the additional heat from rising basaltic magma. ■ The magma heat source may come from a plume of hot magma below a hot spot or from andesitic magma that pools below the continental crust above a subduction zone. ■ Either way, once produced, the rhyolitic magma can rise upward. High-silica magma produced is so viscous that is relatively imobile and is more likely to solidify within the crust without making it to the surface as lava. ○ At subductions zones, magma is produced because water is released/high-water content in the subducting plate lowering the melting point which makes it easier for rocks to melt when heat and pressure increases. ● Divergent boundaries: ○ At the same time, divergent mantle rock is rising to lower pressure and melts in the oceanic lithosphere in a mantle hotspot. Basaltic rock erupts at active volcano/formed at seafloor rift. Partial melting of mantle rock below an oceanic ridge results in basaltic rock. ■ The composition of the basaltic magma becomes more intermediate as it melts and assimilates silica-rich crustal rocks. ■ Magma will always be more felsic than the rock it melts from. Mantle is ultramafic. Melts into mafic. Oceanic crust melts into intermediate. Continental crust melts into felsic. ● Mafic rocks will always solidify ■ Mantle plume at the bottom will result in partial melting of mafic, basaltic rock. Will result in the partial melting of rhyolite rock above. ○ Low silica content (mafic) and low viscosity. ○ Partial melting below oceanic ridge because of decompression in the asthenosphere. ○ Magma formed derived from a silica-poor mantle source so the ocean floor and hot spot volcanoes are made up of low-silica basalt ● In summary: ○ Divergent boundary is basaltic, mafic, and oceanic. Low silica content and low viscosity. Partial melting below oceanic ridge because of decompression in the asthenosphere. ○ Continental divergence and hot spots may sometimes generate mafic magma instead. ● Formation of magma within the Earth can only be caused by depressurization without a change in temperature. ○ Pressure and temperature cannot change at the same time. It is not the removal of ductile rock or an increase in pressure without a change in temperature. Silica ● When rocks are heated, some minerals melt while others remain solid. The higher the silica-content, the easier it is to melt. Therefore, rocks lacking in silica will take longer to melt. ○ Partial melting takes place meaning that the new rock may contain more of low-melting point/increased silica materials than the original rock.

General Notes ● Decompression melting occurs at divergent boundaries. The mantle material is quickly moving up the surface from high pressure to a lower pressure. Also becoming cooler. ● Hot spot failed divergent boundary. Mantle upwelling from below. Stuff pushing upwards and lateral movement. Not the tension needed to create divergent boundary ● Magma does not does not erupt at C-C collision/convergence because continental rock is felsic. ○ It’s higher pressure making harder to make magma. Even if magma is made, it can’t always get up to the surface because felsic is high in silica and more viscous making it harder to erupt. In summary: C-C convergence makes felsic magma that is high in viscosity and hard to erupt ● Felsic minerals have lower melting points meaning they melt first. If it comes in contact with mafic magma it may also melt. Stuff with a higher melting temp it can melt things with a lower melting point. ● Shield volcanoes have a wide breadth. They are low in viscosity meaning they flow faster and wider. ● Cross-section: divergent decrease in pressure, convergent high temps and water felsic when crust. ○ Oceanic hot spot: Decrease in pressure ○ Mid-ocean ridge: Decrease in pressure ○ Subduction: Increase in temperature, high water content, felsic when there’s crust ○ Continental hot spot: Increase in temperature, high water content, felsic ○ Continental collision: Increase in temperature, high water content, felsic ○ Increases in temperatures are because of hot magma rising from below. Whenever there’s subduction zones its water and continental collisions are felsic. ○ Decrease in pressure: ductile, fast-moving mantle material rising from convection. Magma is already in a liquid state from when it rises from beneath the Earth. Poll Everywheres and McGraw Quizzes ● As a rock heats up, minerals will melt in this order: felsic, intermediate, mafic, ultramafic. Magma will always be more felsic than the rock it melts from. ○ Mantle is ultramafic. Melts into mafic. Oceanic crust melts into intermediate. Continental crust melts into felsic. ● Magma forms from partial melting and produces magma with increased silica and viscosity. ● Oceanic ridges and hot spots partially melts the mantle to generate basaltic magma that is low viscosity. Eruptions produce lava that forms shield volcanoes and the ocean floor. ● Subduction zones partially melts mantle (with water) to generate andesitic magma. Moderate-high viscosity. Eruptions produce tephra and some lava that forms stratovolcanoes. ● Rising magma (sometimes from hot spots) melts continental crust to generate rhyolitic magma that has high viscosity. May solidify underground to form granite pluton. Produces tephra and some lava. Phase Changes ● If a rock is wet, it’ll change the slope of the solidus. ● High water content makes it harder for magma to form rigid structures allowing for a lower solidification temperature. Therefore, a rock that’s in between would be solid if dry but liquid/magma but wet. ○ Subduction by itself does not cause melting but when subducting plate as water and subducting it releases water and makes things melt. High water content rock melts and dry rock does not. ○ Subducting crust releases water causing melting temperature of overlying plate to decrease ● On the flipside are continental rocks. These are felsic and high in water. Viscous magma forms and moves upward resulting in a decrease in pressure. It is also cooling and solidifying underground. Magma forms from the high water content. ● It is easier to melt with higher temperatures at the surface because the pressure is lower. ○ Best way to heat up rocks is by having hot rocks from below. Felsic (continental collision) or

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high water content (subduction zones). ● To turn a solid into a liquid or gas need to either increase temperature, decrease pressure, or both ○ Measure temp is kinetic energy of the molecules/amount of movement ○ Increasing temperature=increases kinetic energy. Phase change. ○ Increased pressure packs molecules tighter together making phase change more difficult. Don’t have room to move so they can never act like a liquid even when temperature increases. ○ Pressure decreases easier for molecules to change. ● EASIER TO MELT STUFF AT SURFACE BY INCREASING TEMP ● If something is moving up towards the surface it is cooling down. Geotherm makes it hard for pressure to decrease and temp to increase at the same time ● Magma forms by increasing temperature ○ Hot magma rising from below encounter rocks near the surface and melt them ● Magma forms by decreasing pressure ○ Quickly rising mantle material decreases pressure but maintains heat from within the earth depressurizes and melts. ○ Divergence under continental crust. Mantle materials rising quickly depressurizes making magma and comes into contact with lithosphere which raises the temperature. ● Felsic minerals melt at lower temperatures than mafic minerals. Hot Spots ● A hot spot is an area where tectonic activity is occurring due to mantle upwelling even though there is no plate boundary. Instability at the core-mantle boundary causes a mantle plume to arise led by a hot, turbulent plume head. ● When the plume reaches the top of the mantle, basaltic magma from decompression melting penetrates the lithosphere and erupts as flood basalts. ● As the plate moves over remains of the plume, the plume tail now a hot spot may form a hot-spot volcano. Smaller amount of magma that just creates volcanoes. ● Continued plate movement over the hot spot creates a hot-spot volcano chain. Extinct volcanoes beside active volcanoes. ● Hot spots can lead to felsic or mafic magma formation: ○ Rising (solid) mantle plume decompression melting in the mantle forms mafic magma. Mantle material goes through the ocean crust (mafic-basalt) not a lot to change to composition so it remains mafic and erupts as mafic magma oceanic island. ○ CONTINENTAL: Mafic mantle magma travels through thick continental crust: flood basalt. This is mild. If there is continental you can also have explosive event. Partial melting of continental crust changes composition: intermediate to felsic eruption ● Hot spot versus volcano. ○ Hot spot is tectonic activity/mantle material coming up not at a plate boundary. ○ Hotspots occur when one of the Earth's plates moves over an unusually hot part of the Earth's mantle. These hot areas are usually relatively stationary and result in large amounts of magma rising up, piercing a hole in the plate to form a volcano. As the plates move, a series of volcanoes can form. ● Usually don't see stratovolcano at continental hot spot. Traditional style volcano is stratovolcano that is more explosive and subduction zone like Yellowstone. Miscellaneous Features

● Flood Basalts: Black basaltic rock covers the land. Extrusive igneous rock. Mafic. ○ The result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. ○ Release of gasses and aerosols (suspended liquid particles): CO2 and H2O warm the climate, SOx (sulfur dioxide) and solid cool the climate by reflecting solar radiation while SOx can destroy the stratospheric ozone and warm climate. ○ Famine, SOx created acid rain and fog that damaged crops, fluorine killed livestock ● Decan Traps: The Deccan Traps is a large igneous province of west-central India. It is one of the largest volcanic features on Earth, taking the form of a large shield volcano.[2] It consists of numerous layers of solidified flood basalt. ● Intermediate magma results in explosive eruptions. ○ Subduction zone ○ Volcanoes (cascades) ○ Caldera: Eruption caused mountain to collapse into an emptied magma chamber. A crater that forms when a stratovolcano or shield volcano collapses into a shallow, empty magma chamber below to the volcano. ● Felsic eruptions impact a wide area and may also be associated with continental hot spots. ○ Magma sitting in the earth melting felsic minerals out making more explosive because of high viscosity causing eruptions to occur ○ Yellowstone: Transition from felsic rock coming out to mafic rock coming out all about partial melting of the crust. ■ Columbia River flood basalts. First expression of mantle plume. ■ Forms calderas. An example would be Crater Lake. ● Calderas: Felsic rock. ○ Formed by hot spots. Mantle plume at the bottom will result in partial melting of mafic, basaltic rock. This rises and will result in the partial melting of rhyolite rock above. Products of Eruptions ● Lateral Blast: Volcanic Blasts (driven by gas-rich magmas with intermediate viscosity) that are directed horizontally and more destructive because disrupts a large area ● Tephra: Particles of all sizes that are blasted into the air by an eruption. Blew apart volcanic crater and blasted molten rock high into the atmosphere. A vertical column. Fine ash that spreads and can be carried downwind. Can add weight and clog or damage machinery. Can hurt planes cause engines to fail. Slipper when wet can make cars slip on roads. Can block sunlight and drop temps. ● Volcanic Gasses: The escape of dissolved gasses drives the eruptions that blast tephra high in the air. Three principle gases of an eruption are water vapor, carbon dioxide, and sulfur dioxide (carbon and sulfur can effect global climate patterns or causes death. ● Lava: Low viscosity basalt lava flows can travel long distances and build up into hardened piles. Can gradually build up into a lava dome. ● Pyroclastic Flows: Mixtures of hot gasses and ash, cinders and other volcanic debris which combine to form a dense hot cloud that races down the volcano’s slope incinerating all in its path. Speed and high temps. ○ Sometimes form when large volumes of erupted material rise into the atmosphere and cool. Density of cooling material increases causing it to drop and tumble. ○ Other times volcanic debris spills over the rim of the volcanic vent into unstable materials from earlier eruptions triggering a cascade that flows down the volcano’s slope. ○ Part of the volcano’s flank may collapse and flow downhill ● Lahars: Mudflows formed when fine-grained tephra mixes with water from snowmelt or streams. Can occur from heat of eruption melting ice, creating lahars.

○ Flow mainly down stream channels and carry tons of debris capable of destroying everything in their path. Reduces channels depth and disrupts river traffic. ● Linear fissure: Longer vertical crack in the crust ● Lava Plateaus: Low-viscosity lavas that reach the surface through fissures which are made up of many layers of solidified basalt lava. These represent the largest eruptions. Three Types of Volcanoes: Shield volcanoes, stratovolcanoes, and cinder cone volcanoes. ● Shield volcanoes are broad with gently sloping sides built up from thousands of fluid, low-viscosity lava flows and mafic. ○ Magma rises up through layers of basalt through feeders and erupts making new lava on the slopes and sides. ○ Hawaiian Islands like Mauna Loa highest mountain outside the Himalayas. ○ Low-silica mobile lava creates shield volcanoes. ○ Found above oceanic hot spots or in association with divergent plate boundaries. ● Stratovolcanoes/composite cones are steep-sided and cone shaped ○ Majority of the worlds active volcanoes that form along convergent plate boundaries ○ Violent style of eruption that blasts debris several kilometers into the atmosphere. ○ Called composite cones because they are composed of many layers of volcanic debris, pyroclastic flow deposits, and lavas. ○ Develop from more viscous magmas that shield volcanoes and have a narrower base and more steeply sloping sides. Older flows within and a crater atop. Earthquakes ● Faults versus plate boundaries ○ A fault is an area where displacement of the crust occurs. It might occur at a boundary. A break in the rock along which the rocks have moved relative to each other ○ Plate boundaries are areas that may be made up of multiple faults where motion between plates is observed. After elastic deformation, movement results in brittle deformation of crust along faults. ● Here’s how earthquake predictions typically shake out: stress on the crust builds up over time. This creates elastic potential energy which is released as kinetic energy during the brittle deformation of the crust. ○ Kinetic versus potential energy: ductile earth tends to deform as soon as you put pressure on it meaning it doesn’t store energy. Brittle rocks store the energy and then snap. ○ Elastic deformation occurs along the boundary until it breaks and faults are formed. ○ Analogy: A glacier has flow at the bottom and tries to drag the top of the ice creating cracks ● Movements in the ductile asthenosphere causes movement in more brittle lithosphere. Asthenosphere is moving and causes stress on the stuff above. As a result of tectonic movement, stress builds up along the fault. ○ Stress: Force per unit area. Strain is the response to stress. ○ Ductile=bends/flows, brittle=breaks/fractures, elastic=ductile deformation until braille deformation occurs. ● Transform boundary example: ○ Tend to be close to the surface. A bending/curving shape ○ Strike slip fault releases stress/energy and creates earthquake ○ Rocks form elastically and undergo brittle deformation when stress exceeds rock strength.

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Energy is released when brittle deformation occurs=seismic waves. ○ Movement creates energy that radiates in all directions as of seismic waves ● Elastic rebound model: how long does it take for the stress to build up enough for this to occur. ○ Stress goes up, elastic deformation gets to the breaking point (overcome frictional surface/rocks being still versus moving which results in movement) ○ Energy is released when elastic deformation occurs in the form of seismic waves in all directions. ○ Elastic strain is at its maximum right before the earthquake ● Liquefaction: Loss of cohesion when grains in water-saturated sediment lose grain-to-grain contact. Not on solid rock atop sediments not turned into rock yet and groundwater has an easy job of flowing through. (coastal areas tend to be very wet) ○ The builds and stuff sink into the ground which makes them lean over. How much can this building sway. ● Seismic gaps: An area along the fault that has not experienced earthquake activity or movement at the same rate as other areas of the fault. These can be used to tell us where stress may be building up. ○ If there are seismic gaps this tells us that rocks are locked together and storing elastic energy at this location ● Recurrence Interval: average amount of time between each large (magnitude 8 earthquake event). Used to help calculate the probability of future earthquake events of various magnitudes along a particular fault. ○ calculated average time between past occurrences of random events ○ Go up by an order of 10 in average in relation to the magnitude Tsunamis ● Tsunamis are when there’s a fault occurring in the Earth’s crust underwater. The rock jutts up, displacing the water and creating and upward wave that crashes onto the shore. Subductions zones create vertical movement underwater. ○ Referred to as vertical displacement of the seafloor which results in the displacement of a lot water. ○ Between the earthquakes, the subducting plate is locked and there is a slow distortion of the land. When the earthquake occurs, the struck area ruptures releasing energy. This results in a vertical column of water occurring above the subduction zone. Minutes later the tsunami waves spread left and right. ○ Oceanic plate subducting beneath the continental plate. ● Tsunamis may also occur as a result of landslides. There’s an explosive formed caldera tsunami. The eruptions happen and the stuff collapses inward. The explosive energy creates tsunamis waves on either side of collapsed structures. ○ To generate a very large tsunami, this slide would have to happen very fast and as an essentially coherent block. Flank collapses of oceanic island stratovolcanoes generate waves and tsunamis. ● There are also Atlantic tsunamis like the Canary Island hotspot. ● Tsunamis vertical movement happening under the water that displaces the water colony. We can also see tsunamis from landslides or hotspots. Just need sufficient force to move a vertical column of water. ● Tsunami: Portions of the seafloor move because of fault displacement, ocean floor landslide or submarine volcanic eruption which displaces large volumes of ocean water to create a tsunami. ○ Megathrust earthquakes associated with subduction zones occur when the overriding plate no longer slides over the descending plate as it moves downward into the subduction zone. ○ The leading zone of the overriding plate is carried a small distance downward into the

subduction zone causing the shape of the plate to become distorted as it buckles upward. ○ Eventually the “stuck” fault segment between the plates ruptures generating a giant earthquake and displacing the overlying water in the ocean to produce a tsunami. ○ Specifies where they occur in the world. ○ Water receding from the beach only to be followed by a surge of water inland. Waves of tsunami like all waves have high parts (crests) and low parts (troughs). Water levels may initially rise or fall depending on which part of the wave arrives at the coast first. Earthquake Prediction ● There is a relationship between the recurrence interval and the magnitude. For every increase in magnitude, the recurrence interval goes up by an order of 10 (in other words 10x). ● Probability is the # of ways an event can occur) / (total number of possible outcomes) ○ Example: Probability is rolling a 2 on a six-sided die. 1/6=0.167=16.7% ● When calculating the probability of an earthquake events we use the following formula: (# of earthquake events/time) (*100) ○ Example: there are 6 magnitude seven or greater earthquakes in the past 50 years. ■ 6 (# of events) divided by 50 (time)=0.12. 0.12 times 100 results in a 12% recurrence interval probability. ○ Example 2: there are 546, 5.0-6.9 magnitude earthquakes over 50 years. ■ For probabilities that exceed 100% we use a different time unit like days. (10.92 times 100 is 1,029%) too high obviously. So do the years and then divide again by the number of years. Then multiply by by 100. ■ 546 earthquakes divided by 50 years = 10.92 (earthquakes annual probability. Then 10.9 divided by 365 for days time 100 which is 2.99% chance per day. ○ If we have the average annually (as opposed to something over something like a 50-year span) then we divide by 365 days to know the daily average. ● Recurrence Interval is the inverse of probability: time/# of events ○ Example: If there are 134 events in a year the recurrence interval would be 365/134=every 2.7 days ● Using historical data in averages with the purple dots to predict magnitude later on. ○ Going up one magnitude decreasing the number of events by about ten. as you go horizontal, you are decreasing the number of events/increasing the interval between earthquakes. ○ A magnitude 5 earthquake is ten times more likely than a 6 mag earthquake ● Example: ○ ANNUAL PERCENT PROBABILITY: Figuring out a magnitude 9 earthquake. It crosses at .001. There’s 50 years. ■ Go to the left and find the mag. at the y-axis and see it’s like .001 then move two to the right which would give you .1% to change to percent multiply by 100 ■ 50-year record showed 2 magnitude eight earthquakes. Annual percent probability that these earthquakes will occur in a year. ● 2/50=0.04 * 100=4% ○ RECURRENCE INTERVAL: For a mag 10 earthquake we .0001. Recurrence interval. 1 (year)/.0001 (# of earthquakes per year)=10,000 years ● Seismic hazard is a natural phenomenon such as ground shaking, fault rupture, or soil liquefaction that is generated by an earthquake, whereas seismic risk is the probability that humans will incur loss or damage to their built environment if they are exposed to a seismic hazard. In other words, seismic risk is an interaction between seismic hazard and vulnerability (humans or their built environment). In general, seismic risk can be expressed qualitatively as

P and S Waves ● With every earthquake there is a break, release of energy, and moving outward in seismic waves. ○ Love and rayleigh waves mostly shaking but travel on surface while P and S through Earth. ● P, S, and surface waves are recorded at different seismographic stations. Can use travel times of P and S waves and see the difference in the waves to see where the earthquake happened. The travel time difference to figure out how far away we are from the earthquake focus/distance. ○ P waves are faster (first in the alphabet). Since S is so slow they can’t permeate liquid layers. ○ 3 stations needed to pinpoint the one location that is the correct distance away from all three graphs. The point where they all intersect. ■ The arrival time of P- and S- waves tells us about DISTANCE, not DIRECTION. ■ If less than 3 seismic stations are used, more than one epicenter is possible. ● Resistance to deformation matters. Higher density, higher rigidity=faster movement. ○ Not maintaining a rigid structure (liquid) lower rigidity=less focused/slower movement ○ Even though it is denser when in liquid phases it is slower. Shear energy is lost in materials with no rigidity. S-waves cannot move through liquids. ● As seismic waves move away from the the focus: ○ Shadow zones: Waves bend towards the surface like curtains as they go deeper into the mantle and the center as they move into the core refracted wave like a broken arm. ○ Bending towards the side because waves bend towards the surface the deeper they go into the mantle/go through different phases. Trying to go back out like a curtain. ○ If they get into the outer core (only P-waves) Waves bend to Earth’s center like a circus tent. ○ Bending is from change in speeds. Bend towards material they slow down in ■ Turn towards the slower side or side you stop with like rollerblading and stopping with one foot and turning or a motorcycle ○ Shadow zones: created by bending/refracting. Where P and S waves don’t show up ■ (S-wave) cannot go through certainty layers ■ P-wave speed that they’re going through different densities. Cannot measure them directly where they are. They refract to certain spheres and miss others. ● P waves versus S waves ○ P waves can travel through liquid and solids and gases, while S waves only travel through solids. ○ P waves have a higher/faster velocity than slower S waves ○ P waves are compression waves and longitudinal while S waves are like snakes. ● Body waves: Can be divided into P and S waves ● Highest velocity known as primary or P waves. ○ First to arrive at a distant seismograph. ○ Compress the material through which they pass the same way that a sound wave compresses air. Molecules vibrate parallel to the travel direction just as a vibration passes along a Slinky toy. ○ P waves travels at speeds of 4 to 6 kilometers per second in the crust. ○ Travels faster in the mantle and core because of different compositions and greater density of the materials. ○ Expanding and compressing which is making it vibrate in the same direction that the wave travels. Traveling the length of it. ● Shear waves or S-waves

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○ The motion of S-waves is like a vibration moving along a rope when it is given a sharp snap downward. Vibration occurs perpendicular/up and down to the direction the waves travels. Like a roller coaster. ○ Cannot pass liquids so useful in inferring the physical state of rocks below Earth's surface (moltens or solid). ● Velocities of both types of body waves are lower in loose materials (sand, gravel) and partially melted rock. Higher in solid materials such as rock. Fastest seismic waves are P waves. S waves are intermediate and surface waves are the slowest. ● The farther away a seismograph is from the earthquake focus, the longer it take for seismic waves to reach it. ○ Both P and S waves are generated at an earthquake focus as a result of movement on a fault. P waves reach first and surface waves last because the body waves travel take a more direct route through the Earth’s surface. ○ Determine the location, time, and size of the location scientists use the times they arrive and amplitudes. ■ Because S waves are slower than P waves the time interval between their arrival increases the farther the station is from the epicenter. ■ Difference in arrival time can be used to determine the distance of the station from the source. ○ Data from a single station is not enough to determine location because it only shows distance. Therefore, you need data from multiple stations to find the common intersection point of several circles. ● The speed of P waves and S waves increases as they travel deeper into the Earth's mantle. The direct P wave arrives first because its path is through the higher speed, dense rocks deeper in the earth. ● S-waves will not be able to enter the liquid outer core ● Seismic waves move faster as you go deeper into the mantle and slow down or stop in the liquid outer core. Geothermal Gradient versus Solidus ● Outer core is only conditions: pressure/temperature in which rocks are liquid. Asthenosphere has magma chambers and blobs of liquid ○ Solidus: Line showing where phase change occurs. In this image for basalt (mafic). Straight diagonal rock. ■ Melting curve with depth. At this temperature/depth point on the graph its a solid but if you cross to the right of the blue line its a liquid. The point at which a solid will melt or liquid will solidify. Temperature at which something melts or solidifies changes with pressure. ○ Geotherm: natural temperature/ pressure changes with depth in Earth ■ never crosses the solids meaning it never increases so much that it liquifies/never crosses blue line meaning its always solid. Deeper down in earth hotter it gets ○ In the asthenosphere geotherm and phase change gets close. Weak rock it could flow. Ductile can bend or deform easily.

Energy Resources ● Renewable are things like solar, wind, hydroelectric, tidal, and geothermal resources ○ Flux in is equal to flux out ○ More coming in than going out ○ Most renewable energy goes to electricity generation and then residential, commercial, and industrial uses. ● Non-renewable energy resources ○ Fossil fuels (natural gas, oil, coal) ○ Nuclear ○ Biomass like burning charcoal, wood, or manure (may be renewable if used at a rate slower than the replacement rate) ○ Petroleum is mostly used towards transportation (some goes towards industrial uses) ○ Natural gasses goes to industrial, commercial, residential, and electricity generation ● We see more natural gasses and increase coming from fracking opposing/decreasing the usage of coal ○ A shift in the energy landscape: “unconventional” reserved e.g. from fracking and shale gas, have increased natural gas availability in the U.S. and elsewhere ○ Fossil fuels are the most energy dense substances on earth besides radioactive stuff ■ Density is mass/volume. Energy density is energy produced per mass ● Formation of fossil fuels: Fossil fuels form from plant matter (coal) and marine plankton (oil) that were buried under low-oxygen conditions, preventing decomposition of organic carbon into CO2. ○ Organic matter laid down with no oxygen allowing it to decay. Buried in organic carbon form and eventually become a fossil fuel. ○ Giant plants died in swamps and buried under dirt and heat and pressure turned it into coal. We dig down to reach them. ○ Formation of petroleum and natural gas. Small animals died and went to the bottom of the ocean sand and silt formed over them. Heat and pressure turned the remains into oil and gas. We dig down to reach oil and natural gas deposits. ● Coal mining. You find horizontal coal layer and go horizontal leaving behind pillars of coal so that it doesn’t collapse behind you rather then digging behind you. ● Coal formation: organic matters accumulated without decomposition ○ Swampy areas: (still water=low oxygen=hydrocarbons preserved). stagnant water. not oxygenated. microorganisms use up the oxygen and it’s really hard for anything else to grow. ○ different from something like the beach. ○ Preservation of carbon in low-oxygen environments ● The deeper the coal is buried: ○ Increase in coal grade, increase in energy density, increase in carbon. ○ Decrease in volatiles like h2o and co2 ○ Anthracite's highest carbon content and lowest emissions makes it the best. ○ If peat is buried, water and other non-carbon compounds are squeezed out and hydrocarbons are concentrated to make a cleaner-burning, more energy dense fuel. ● We will never run out of coal in the US. Not energy efficient or good for the environment compared to the amount of pollutants coming out of it ● ●

● ○ ● Activities ● The recurrence interval is the length of time necessary to build up enough stress to cause a fault to break again. ● Elastic rebound model effects the recurrence interval at a fault because the elasticity of rocks in the area controls how long it takes for the rocks to snap. if the rocks are elastic rather than brittle it can take more stress/bend/deformation and take longer to snap again. More elastic=longer periods. ● Formula for recurrence interval is time/# of events ● The probability corresponds to the the number of earthquakes that occur per year of average and the recurrence interval is the number of days that pass between each quake on average. Energy, Mineral, Water Resources 16. Interpret diagrams illustrating U.S. energy consumption in terms of the energy sources, uses, and wasted energy. a. Why is coal consumption in the U.S. decreasing? b. What are renewable energy resources primarily used for? 17. Compare and contrast how coal, natural gas and oil form, including the environmental conditions, burial conditions, and how temperature and pressure control the energy density of the fuel produced. a. Why do peat and kerogen form in still water? b. How does energy density change with depth of burial? 18. Describe how oil accumulates in conventional oil reservoirs, and how oil is stored, chemically altered, and/or extracted in unconventional oil reserves. a. What is the function of cap rocks and oil traps in a conventional oil field? b. How are tar sand altered after mined? 19. Differentiate between alternative energy sources based on whether or not they are renewable and the energy conversions required to produce electricity a. Compare and contrast hydroelectric and wind power in terms of how the electricity is generated. b. How do nuclear power plants generate energy? 20. Differentiate between “element,” “mineral,” “rock,” and “ore,” a. A rock that was not previously considered mineral ore now is. What change could have lead to this redefinition? b. What are the defining characteristic 21. Describe the processes of mineral exploration, extraction, and beneficiation, including steps

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in the process that consume energy and/or generate waste. a. How do geoscientists look for mineral ore before digging the mine? b. Compare and contrast surface (open-pit) mining, e.g., for iron ore, and underground mining, e.g., for mica, in terms of waste generation. 22. Define watershed and drainage divide and describe the general direction of surface and ground-water flow through a watershed. Describe factors that could make stream discharge change over time. a. What divides one watershed from another? How are watersheds named? b. How does stream discharge change moving from the source to the base of a river? 23. Rank the magnitude of flood events and use this ranking to calculate the recurrence interval and annual percent probability for flood events. Use the best fit line on a recurrence interval graph to determine the discharge of a flood event. a. Look at the best fit line on a graph to find the recurrence interval for a flood with discharge of 500 cfs. b. What is the annual percent probability of a 50-year flood? 24. Calculate the discharge of a river as a specific point. Read a flood hydrograph, including estimating the shape of a flood hydrograph for upstream and downstream locations. a. A river is 20 feet wide and 5 feet deep on average. The speed is 1 ft/sec. What is the discharge of this river? b. A flood event occurs near the source of the river. How would the shape of the flood hydrograph change as the floodwaters move downstream? Earthquakes 8. Differentiate between [seismic] risk and [seismic] hazard a. How could you decrease the seismic risk of a region even if you could not decrease the seismic hazard? 9. Differentiate between P- and S- waves in terms of their velocity, the direction of wave/particle movement, and their ability to travel through solids/liquids. a. Looking at 3 seismograms and a p- and s- wave arrival time graph, be able to determine the distance each is from the earthquake epicenter 10. How does the movement of seismic waves inform us about the Earth’s interior? a. What happens to p-waves as they travel through the Earth? 11. Define elastic rebound theory and use this theory to explain concepts such as seismic gaps and earthquake reoccurrence. a. Why are areas along a fault that have not had many earthquakes likely to see movement sooner than an area along the fault that HAS seen movement? b. When is elastic strain at its maximum? 12. Explain how earthquakes can cause tsunamis, and identify the type of boundary that

typically cause tsunamis. a. A magnitude 9 earthquake occurs at a transform boundary under the Pacific Ocean, and a magnitude 8 earthquake occurs at a subduction zone boundary under the Pacific Ocean. Which causes a tsunami? Why? 13. Be able to use seismograms showing P- and S- wave arrival times pinpoint the epicenter of an earthquake. a. Looking at 3 seismograms and a p- and s- wave arrival time graph, be able to determine the distance each is from the earthquake epicenter 14. Use historical earthquake to calculate annual percent probability of an earthquake event, and use a graph of recurrence interval to estimate the probability of a future earthquake a. What is the annual percent probability of an earthquake with a recurrence interval of 1,200 years? 15. Explain how scientists use historical earthquake data to predict the probability of future earthquake in that area. a. How can scientists estimate the probability of a magnitude 8 earthquake if no earthquakes of that size have been seen in the historical record? Volcanoes, Magma, and Hot Spots 2. Match melting process with tectonic setting, magma composition (e.g., mafic or felsic), magma source, type of volcano observed, and volcanic hazards. Describe why they match the way they do. a. At which plate boundaries do we see magma forming due to decompression melting? 3. Look at a cross-sectional diagram of a tectonic boundary, and be able to explain where magma forms and why, and the type of magma and eruption expected a. How is magma generated at subduction zones? How does this magma change if it travels through continental lithosphere? 4. Describe partial melting, and how a mafic magma can become more felsic as it travels through continental crust. Describe in detail how mafic and felsic magmas differ. a. How does magma composition change during partial melting? b. How does this impact viscosity and eruption characteristics? 5. Differentiate between mafic and felsic magma in terms of composition, viscosity, and eruption hazards. a. Which magma has more silica? Higher viscosity? 6. Explain how hot spots form, and why features observed at continental and oceanic hot spots differ a. How could you differentiate subduction zone volcanic islands from hot spot volcanic islands?

7. Describe geologic features (e.g. volcanoes, flood basalts, calderas) and processes (e.g., decompression melting) that correspond to hot spots. a. Describe the geologic setting of caldera-forming hotspot, and why calderas form there.

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