Exam 1 --- Geoscience

Unit 1 — Plate Tectonics

  • Know Earth’s four layers

    - Crust : thin, outermost layer [continental & oceanic crust]

    - Mantle : thick layer beneath crust, composed of silicate rocks in iron & magnesium

    - Outer core : liquid layer made of molten iron & nickel

    - Inner core : solid sphere composed mainly of iron & nickel

  • How the Earth acquired its internal heat

    - Planetary accretion, heat collisions, and radioactive decay

    - Planets melt inside —> differentiation —> heavier elements sink to form core & lighter elements rise to form crust & mantle

  • Know why the interior of the Earth is layered

    - Heavier elements sink to form core & lighter elements rise to form crust & mantle

    - The layers froze in place as the Earth cooked

  • Why the outer core is a liquid, but the inner core is solid

    - Outer core = liquid b/c it’s the only layer that remains hotter than its melting temperature

    - Inner core = solid b/c it is under more pressure

  • What lithosphere and asthenosphere are

    - Lithosphere = strong outer shell of the Earth consisting of the crust & uppermost [coldest & strongest] layer of the mantle; can break but doesn’t readily flow

    - Asthenosphere = weakest layer of the mantle [flows readily] & underlies the lithosphere; allows tectonic plates to slide around the surface of the Earth. Flows like fluid, but is a solid

  • Know the evidence that Wegner used to suggest that the continents drift

    - The continents : Fit together like a puzzle

    - Paleoclimate : glacial deposits in tropical regions & tropical plants in glacial regions

    - Rocks & structural similarities : matching mountain ranges on different continents & identical volcanic flows [Atlantic]

    - Fossils : non-swimmers/same species found in modern oceans

  • How we know that our magnetic field has reversed itself many times

    - Magnetic lineation’s on the ocean floor show symmetrical patterns of polarity

    - Paleomagnetism in rocks records past magnetic orientations

  • What a mid-ocean ridge, a subduction zone, and a transform plate boundary are

    - Mid-ocean ridge : where new ocean plate is created [new crust forms & a divergent boundary; Mid-Atlantic Ridge]

    - Subduction zone : one plate sinks beneath another & a convergent boundary [Japan Trench]

    - Transform plate boundary : Plates slide past each other horizontally [San Andreas fault]

  • What a passive plate margin is

    - When a boundary between continental crust & oceanic crust is not a plate boundary [Eastern U.S. coast]

  • What a supercontinent is

    - a massive landmass formed by the merging of multiple continents [Pangaea]

  • What caused the high topography of the Himalayas and Tibet

    - Caused by continental collision between the Indian and Eurasian plates

  • What the Wilson cycle is

    - It describes how continents break up and then rejoin

    - formation, expansion, contraction, & closure due to plate movements

  • Whether convection can occur within a crystalline solid

    - No it can’t b/c it requires fluid-like behavior, a crystalline solid conducts heat via conduction

  • What drives plate tectonics

    - mantle convection, slab pull, & ridge push

  • The components required for Earth’s magnetic field

    - liquid outer core

    - rotation of Earth

    - convection currents in the molten iron

  • The consequences of losing our magnetic field

    - Our electrical grid would have major problems

        1) compasses would go crazy

        2) The Auroras may be visible every night [everywhere]

        3) more charged particles reaching Earth [power outages & broken satellites]

        4) migratory animals that use the magnetic field [birds, turtles, bees, salmon] will have difficulties navigating

        5) no mass extinctions

Unit 2 — Earthquakes

  • The largest earthquakes to occur in the past 100 years

    - 1960 Chile [9.5]

    - 1964 Alaska [9.2]

    - 2004 Sumatra-Andaman [9.1]

    - 2011 Tohoku, Japan [9.1]

    - 1952 Kamchatka, Russia [9.0]

  • What elastic rebound and stick-slip behavior are

    - Elastic rebound : the crust bends like rubber [storing energy], then unbends [releasing energy]

    - Stick-slip behavior : faults remain stuck while energy builds, then suddenly slips when energy is released

  • What an asperity is

    - Rough spots along the fault where friction is high; store stress & release it during earthquakes [the most intense shaking]

  • How do the plates deform before compared to during a subduction zone earthquake

    - Before : plates bend & accumulates strain; overriding plate may bulge upward

    - During : sudden release of strain causes the overriding plate to.snap downward, generating seismic waves and often tsunamis

  • The settings [type of plate boundaries, direction of relative plate motion] in which thrust, normal & strike-slip faults occur

    - Thrust [Reverse] : convergent and compression [plates collide]

    - Normal : divergent & extension [plates pull apart]

    - Strike-slip [transform] : transform & horizontal sliding [shear]

  • How movies generally and incorrectly depict earthquakes

    - exaggerating shaking/unrealistic destruction

    - instant ruptures/gaps across entire faults

    - visible cracks opening in the ground

    - ignoring real seismic wave behavior [wave propagation]

  • The types of seismic waves and their basic properties

    - P-Waves [primary/pressure] —

            —> push-pull motion [compresses then expands]

            —> travels through solids, liquids, & gases

            —> fastest seismic waves [first to arrive]

            —> compressional waves; move along the direction of propagation

    - S-Waves [secondary/shear] —

            —> Up-down or side-to-side motion

            —> doesn’t travel through liquids

            —> slower than P-waves [second to arrive]

            —> shear waves; move perpendicular to the direction of propagation

    - Surface Waves —

            —> Love waves :

                        ~ side-to-side motion

                        ~ along with Rayleigh waves, they are last to arrive b/c of the most shaking

            —> Rayleigh waves :

                        ~ Up-down [rolling] motion

                        ~ along with love waves, they are last to arrive b/c of the most shaking

  • How many seismograms are required to locate an earthquake

    - Three seismograms are required to triangulate the epicenter

  • How we know the outer core of the Earth is liquid and the inner is solid

    - Outer core is liquid = S waves don’t travel through the outer core but P waves do [S wave shadow zones]

    - Inner core is solid = P wave refraction/reflection patterns confirmed

  • How earthquake magnitudes are related to the relative magnitude of shaking

    - Intensity refers to the effects that earthquakes have

    - Magnitude refers to energy released

  • The theoretical maximum earthquake magnitude

    - For every whole number increase in magnitude, the amplitude of shaking goes up by a factor of 10

    - For each increase in 1 in magnitude, the energy released is about 30 to 32 times greater

    - Cannot physically rupture past 10

  • The influence of loose sediments on earthquake shaking

    - Amplify seismic waves —> increase intensity & duration

    - leads to liquefaction, landslides, and structural damage

  • What earthquake intensity [Mercalli Scale] measures and the factors that influence it

    - the shaking that people and buildings actually feel

            —> based on felt reports

            —> used to estimate the size of historic earthquakes

            —> means of estimating how destructive an earthquake was likely to be

  • Why earthquakes are felt farther away in the eastern US compared to the western US

    - older, denser bedrock transmits seismic waves more efficiently

    - Western US has fractured, younger crust that absorbs energy faster

Unit 3 — Earthquake Prediction and Mitigation

  • The relationship between the biggest magnitude earthquakes and the deadliest

    - Biggest earthquakes : Largest stress build up & longest faults

    - Deadliest earthquakes : largest population & bad building practices

  • Why earthquakes are difficult to predict

    - No reliable precursors

    - Don’t know how much stress is required to initiate an earthquake

    - Can’t measure stress in the Earth to see what is happening on faults

  • What forecasting earthquake probabilities is based on

    - Slip deficit rates and time since the last earthquake

  • The problem with earthquake precursors

    - No reliable precursors at the moment

    - Foreshocks/unusual animal behaviors are inconsistent & can occur w/out following a major earthquake

  • How GPS is used to predict how big the next earthquake in a region is likely to be

    - Helps measure slip deficit rates

    - The amount an earthquake will need to slip to reduce elastic stress build-up

    - Knowing these, helps forecast the potential size of the next earthquake

  • Why the US Geological Survey believes there is a high seismic hazard in the Midwest

    - Historical data of 3 of the largest earthquakes that occurred in New Madrid or the Midwest

  • Things to do to minimize earthquake deaths, especially your own

    - [Indoors — developed country] : stay inside, drop cover, and hold on; use doorway for shelter ONLY if it’s strongly supported, loadbearing doorway, avoid elevators

    - [Indoors — 3rd world/developing country] : get out the building as fast as possible

    - Outdoors : stay outdoors and move away from buildings

  • Why diagonal beams help buildings be more resistant to earthquakes

    - Provide resistance to shearing that often causes buildings to collapse

  • The percent chance of avoiding collapse during an earthquake that California building codes require

    - Have 90% chance of avoiding total collapse

    - 10% of buildings could collapse during the next major earthquake

  • The importance of a proper foundations and what liquefaction is

    - A process in which a saturated/partially saturated soil substantially loses the strength & stiffness due to an applied stress as shaking during an earthquake’

    - Buildings can fall over during an earthquake due to liquefaction, where shaking temporarily turns wet sediments into a fluid

  • How we can keep a building from swaying too much during an earthquake

    - Concrete floors are incredibly heavy & without proper steel reinforcement & lateral support, it can lead to a building to pancake during an earthquake

    - Base isolation systems decouples a building from its foundation, allowing it to move independently during an earthquake

  • How an earthquake early warning system works.

    - Seismic waves travel slower then the speed of light.

    - One can detect an earthquake & communicate a warning ahead of the shaking [on phone]