USC GEOL 130 Mid-Term 3 – Flashcards
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Time Series Plot
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Temporal series of a value (any graph with time and one other variable)
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Two Definitions of Time
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A fundamental dimension of the universe in which events occur in a sequence and a human construct used to quantify motions by comparing the durations of events and the intervals between them.
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How many arrows of time are there?
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6
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What are the 6 arrows of time?
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Entropy arrow, cosmological arrow, radiative arrow, quantum arrow, causality arrow, and psychological arrow
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What is the influence of technology of time?
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Clocks (all kinds - water, hourglass, sundials) enable humans to quantify time
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What is a second defined as?
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Around 9 billion oscillations of a cesium atom
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Christian Huygens (1657)
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Pendulum clock
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Robert Hooke (1658)
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Spring clock
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Carl August (1839)
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Electronic clock
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Clock 1948
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Atomic clock
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What are the most advanced clocks we have?
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Laser clocks
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Catastrophism
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Accepted primarily up to 1850, Earth was stable until some act of God caused a huge natural disaster that shifted a bunch of stuff around on the Earth, fit with a young Earth
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In the Middle Ages, what did most people believe the age of the Earth to be?
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Around 6000 years old
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Leonardo Da Vinci 1500
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Deduced that the fossils he found in rocks were found in communities and groups because they existed at the same time, combatted catastrophism because this idea fit better with seasonal flooding
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Steno 1669
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Found fossils beneath buildings, so thought that the Earth must be greater than 3000 years old
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Robert Hooke 1670
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Fossils are the remains of old living organisms who didn't live at the same time -> could use this to date rocks
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William Smith 1700's
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Modern geologic mapping started
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1785-1795 James Hutton
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"Founder" of modern geology - recognized that the rock record is important
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Uniformitarianism
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James Hutton 1785, gradual changes in the Earth, internal dynamic heat engine
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Steno (1600's)
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Superposition, original horizontality, and lateral continuity, unconformities, fossil succession, cross-cutting relationships
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Superposition
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Oldest layer at bottom, youngest on top
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Original Horizontality
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Bumps and stuff in the Earth must have gone through something to disturb the horizontal layers
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Lateral Continuity
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Layers were once continuous, but may now be cut by a river or body of water or something
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Unconformities
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Notable changes in the rock sequence (e.g. angular, non-conformities, disconformities and paraconformities)
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Fossil Succession
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Fossils can be used to date the rocks, fossils go from oldest to youngest
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Crosscutting Relationships
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Something that cuts across another must be younger than the material being cut
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What is the time scale hierarchy?
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Eons, eras, periods, epochs
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What are the eras for the Phanerozoic eon?
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Paleozoic, Mesozoic, and Cenozoic
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What are the eons that make up the Precambrian eon?
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Hadean, Archean, and Proterozoic
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Is the geologic scale a relative or absolute scale?
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Relative
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Relative Dating
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Can tell age relative to other things
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Absolute Dating
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Can calculate an age in millions of years
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What are some seasonal patterns that can help to date something absolutely?
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Tree rings, growth rings on shells and fish scales, varve sequences
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Wilhelm Roentgen 1895
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Discovered x-rays
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Henri Becquerel 1896
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Discovered weak emissions from uranium compounds - called radioactivity by Marie Curie
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Radioactive Decay
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Some isotopes are unstable and decay at a constant rate to a stable configuration. Parent isotope --> stable daughter isotope + heat + nuclear particles
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The average rate of decay is only a function of...?
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Time and amount of the parent isotope
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Half life
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Time it takes for half of the parent isotopes to decay
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Ernst Rutherford 1907
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Suggested that he could use radioactive decay to date rocks
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What is the formula for the age of something undergoing radioactive decay?
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Amount daughter/amount parent*decay rate
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What are some assumptions we must make in order to use radioactive decay as a method of absolute dating?
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We can measure the decay constant, we can accurately measure the amount of parent and daughter isotopes, closed system
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Who was the first to use radioactive dating to determine the age of a rock?
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Bruce Boltwood - he got some around 2.2 billion years old, proving that the Earth was older than 6000 years old
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When you combine the geologic record with absolute dating what do you get?
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A calibrated time scale
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What is the accepted age of the Earth today?
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4.55 +- 0.7 b.y. old
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What is the age of the sun?
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4.5-5 b.y. old
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What is the age of the moon?
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3-4.5 b.y. old
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What are the ages of meteorites?
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4-5 b.y. old
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What is the age of the oldest known galaxy?
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10-15 b.y. old
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What is the age of the oldest atoms?
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7-15 b.y. old
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What is the age of the universe?
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13.75 b.y. old
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What are the implications of cosmological dating?
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Universe has a finite age, much older than previously thought, our solar system came about in the latter 3rd of the universe's existence, atoms are just getting recycled
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When was the beginning of geophysics?
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After Newton's laws and around the start of geologic mapping (1700s)
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What was the average density of the Earth found in the 1700s?
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5.5 g/cm^3
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James Hutton's Beliefs
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Dynamic view of Earth as an internal heat engine, igneous rocks formed by melting and intruding upwards, uniformitarianism (Earth is slowly evolving over time), Earth history is very old
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JD Dana 1873
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Meteorites are parts of planets
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Three main divisions of earth
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Core, mantle, lithosphere
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1934 W.M. Elsasser
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Found that the flow in the outer core causes Earth's magnetic field
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What are the divisions of a meteorite?
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Iron core and achrondritic outer parts
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What makes up geophysics today?
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Gravity, magnetics, heat flow, seismic waves, Earth precession
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What are the two parts of Earth's core?
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Solid and liquid
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What are the two parts of the mantle?
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Mesosphere and asthenosphere
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Which part of the mantle melts and flows the most?
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Asthenosphere
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What are the four parts of the lithosphere?
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Solid mantle, moho, oceanic crust, continental crust
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What are some observations that supported continental drift?
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Similar fossils on different continents, continuous mountain ranges, puzzle-piece shapes
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F.B. Taylor 1908-10
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Argued for continental drift, tried to explain orogenic (mountain) belts, discovered midatlantic ridge, also believed that continents were derived from the North Pole, gravitational forces moved continents, quickly disregarded
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Alfred Wegener 1910
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Noticed puzzle-likeness of continents, shared glacial and other geologic features, shared plant and animal fossils, shared climatic zones, reconstructed Pangea, still thought gravity and tidal forces of sun and moon did it, islands are parts of continents left behind, ideas were not generally accepted because no one agreed about how continents moved
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What were three theories (before ocean floor spreading) that explain the motion of the continents?
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Former continents sinking and ocean rising, continental drift, both ocean and continents pulled apart
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Arther Holmes 1945
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Proposed mantle convection as the cause of continental drift
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Upflowing
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Rifting or pulling apart
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Downflowing
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Trenches, zones of collision, orogeny, earthquakes, magmatism
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Harry Hess WWII
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Used sonar to record bathymetry, we now had maps of the ocean floor including mid-oceanic ridges, trenches, transform faults, and island chains
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What is in the center of a mid-oceanic ridge?
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Axial valley
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Why do transform faults exist?
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Plates aren't flat
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What is a hotspot?
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A place where asthenospheric upwelling is relatively fixed in relation to the lithosphere
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What can hotspots create?
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Island chains
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What is paleomagnetism?
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Rocks have certain magnetic minerals that can help reveal the magnetic polarity of the Earth at a certain time
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What is magnetic polarity?
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It means the Earth's polarity isn't fixed and has shifted and flipped over the years
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What does paleomagnetism give us?
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Latitude (N-S movement of continents), direction to magnetic pole, and polarity of Earth's magnetic field
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Are ocean floors younger or older than continental plates?
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Younger (constantly being recycled)
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Plate Tectonics New Paradigm
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Harry Hess was heavily involved, MORS, trenches, continental plates move driven by mantle convection and SFS, different from continental drift theory since oceans are neither old nor stable
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What are the 7 large plates of the lithosphere?
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Australian, Pacific, North American, South American, Eurasian, African, Antartic
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What are the three main types of plate boundaries?
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Convergent, divergent, transform
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What are the more explosive volcanoes found alongside?
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Trenches
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Where are most earthquakes found alongside?
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Trenches
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Who had the idea of an Earth-centered universe?
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Aristotle/Ptolemy
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Who had the idea of a heliocentric system?
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Copernicus
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Who did a lot of work to prove this heliocentric system?
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Galileo
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Who came up with the mathematical relationships of the heliocentric universe?
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Newton
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Hubble's Law
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The farther away galaxies are, the faster they're moving away (expanding universe), allowed us to reverse the process to estimate the time of the Big Bang
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What scientific theory does the Big Bang Theory fit best with?
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GTR, they both agree on singularities
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What is a singularity?
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All mass at one point (massive black hole)
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Can science address the universe before the Big Bang?
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No
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What were the stages of formation in the Big Bang?
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Near immediately subatomic particles formed, then they formed a nuclei, then it took around 500,000 years to form atoms, then material condensed into stars planets and galaxies due to gravitational attraction
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Evidence for Big Bang
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Hubble's law (accelerating red shift of stars), background radiation, and the GTR
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What is stellar red shift?
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We study the light intensity of stars once, then when we do it again the intensity has lowered (red shift), meaning that the star is moving away from us, we interpret this as an expanding universe
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Spacetime
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Four-dimensional continuum, need four real numbers to identify one point (called an event), distance between two points is called a spacetime interval
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What are some ways we can measure star distance?
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Parallax, stellar motions, moving clusters
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What is background radiation?
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Two guys who worked at a phone company discovered faint microwave signals that was the same in all directions. This was the result of the big bang explosion
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If curvature of the universe is positive then...?
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The universe has a finite size
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Stellar Evolution I
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Form from gas nebula by gravitational attraction, H+H contracts to form He, heat and pressure balance gravitational force when star is stable, when H fuel is gone, star collapse to white dwarf
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Nebular Hypothesis
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5 b.y. ago nebula started to contract and spin, ultimately formed galaxies
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Stellar Evolution II
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Stars like our sun become Red Giants and then White Dwarfs, but much larger stars turn into supernovas and even black holes if they are large enough
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Black Holes
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Region where no light escapes surrounding a singularity
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Evidence for Black Holes
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Gravitational force is huge, perpendicular energy columns, supernova that turn into dark regions, quantum particle behavior at event horizon
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Quasars
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Giant black holes that pulse
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Bosons
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Massless particles that carry out four fundamental forces in universe, formed with anti-particle and recombine and annihilate each other
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Dark Matter
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Explains light bending, gravitational lensing, and Pioneer anomaly
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Fritz Zwicky 1934
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Postulated dark matter
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Dark Energy
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Form of energy with a strong negative pressure acting against gravity, wanting to expand the universe
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The total mass/energy of the universe is made of...?
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4% visible matter, 21% dark matter, 75% dark energy
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What is chaos qualitatively?
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A class of systems with unpredictable, but not random behavior embodied within the mathematical field of dynamical systems (highly sensitive to initial conditions - deterministic)
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Randomness
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Behavior or value independent of previous behavior or value
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Discreteness
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Since we only measure systems at discrete times (though the systems are continuous), we have incomplete knowledge of what is happening between the measurments
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Dynamism
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Non-linear systems that can change their behavior through time (we cannot predict it)
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Feedback
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Nonlinear systems - future value of a process depends on past value of a process. Positive (goes same way), and negative (goes different way)
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Edward Lorentz 1917-2008
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First to use equations to try to predict weather, when he made small changes sometimes he got big changes in output
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Butterfly Effect
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Chaos: if a butterfly flaps its wings then it may mean that it will rain tomorrow
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Dynamical Systems
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Mathematical equations that encompass chaos incorporating feedback
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How can you quantify chaos?
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Time series, phase portraits, strange attractors, limit cycles, bifurcation plots
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Fractal Systems
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Have self-similarity
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Benoit Mandelbrot 1924
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Interested in visual patterns of variability, spatial - length of coastlines, temporal - cotton prices, founded Noah and Joseph effects
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Noah Effect
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Sudden discontinuous changes can occur
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Joseph Effect
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Persistence of a value can occur for a while yet suddenly change afterwards
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Fractal Patterns
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Spatial characterization of temporal processes of dynamical systems
