Geology Terms: Time, Earth's Structure, and Plate Tectonics, Quizzes of Geology

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TERM 1 Relative Time DEFINITION 1 -Older vs. Younger -Relative time scale -based on fossil records TERM 2 Absolute Time DEFINITION 2 -Radioactive age dating -Unstable isotopes break down - some elements can't be used because of half-life -Ex: carbon can't be used to date things millions of years old TERM 3 Half Life DEFINITION 3 -there won't be enough mineral left to measure after about 4 half lives -Uranium, Potassium: half-lives in billions of year TERM 4 Age of Earth DEFINITION 4 -4.6 billion years -dating of meteors and other space rocks TERM 5 Oldest Continental Rocks DEFINITION 5 -4 billion years old -found at the centers of continents TERM 6 Oldest Oceanic Rocks DEFINITION 6 -200 million years old -found at plate boundaries TERM 7 Oldest Fossil Bearing Rocks DEFINITION 7 ~570 years old TERM 8 Ages of Sun and Other Planets DEFINITION 8 -4.6 billion years -(same as Earth) TERM 9 Evolution of the Solar System DEFINITION 9 1) Dust Cloud 2) Dust cloud collapses -> hydrogen fuses to form helium ->gives off energy -3) Sun lights up-> blows away excess material -terrestrial planets are too light to hold on to hydrogen and helium TERM 10 Big Bang DEFINITION 10 ~15 billion years ago -Know this by observing the speed that galaxies are moving away from us, we can conclude that they were all in the same place about 15 billion years ago TERM 21 Asthenosphere DEFINITION 21 -located below the lithosphere -part of mantle that lies below the lithosphere TERM 22 Mantle Convection DEFINITION 22 Mantle convection is the slow creeping motion of Earth's rocky mantle in response to perpetual gravitationally unstable variations in its density. TERM 23 Hot Spots DEFINITION 23 -Streams of molten rock arise deep inside the Earth and move upward through the crust to erupt on the surface or seafloor. As seafloor spreading moves the crust over these hot spots eruptions can create chains of seamounts and islands, such as the Hawaiian Islands TERM 24 Continental Collision DEFINITION 24 Continental collision is a phenomenon of the plate tectonics of Earth that occurs at convergent boundaries when both boundaries are land TERM 25 Nature of Seismicity at Each Plate Boundary DEFINITION 25 ???? TERM 26 Deep Focus Earthquakes DEFINITION 26 A deep-focus earthquake is an earthquake that occurs at depths between 300 and 700 km beneath the Earth's surface. -generally occurs at subduction zones and oceanic- continental convergent boundaries TERM 27 Wegener's Evidence for Continental Drift DEFINITION 27 -Fit of continents -300 million year old southern ice sheet - 250 million year old deserts -migration of species from paleontological record TERM 28 Other Evidence for Continental Drift DEFINITION 28 -Computer fit of continents (includes continental shelf) - Earth's magnetic field -Remnant magnetization - Paleomagnetic polar wander curves -Linear magnetic anomalies parallel to the mid-ocean ridges TERM 29 Earth's Magnetic Field DEFINITION 29 -Dipole field -Magnetic field=direction compass needle points at every point in space TERM 30 Ferromagnetic Materials DEFINITION 30 -can be magnetized -most important material: Magnetite or "loadstone" -In high temperatures, every atom in a ferromagnetic material acts as a magnet, there is not remnant magnetization because each atom cancels each other out -as the material cools, the atoms cluster into magnetic domains when they drop below the Curie temperature (~640 C), From here, it can be magnetized - if you cool a material through its Curie temperature n the presence of a magnetic field, it will assume the same magnetizati TERM 31 Paleomagnetic Polar Wander Curves DEFINITION 31 formed by figuring out angle to North Pole from rocks collected at various points on the current continental configuration -makes it appear that the North Pole was wandering... actually the continents were -SEE explanation in notes TERM 32 Linear magnetic anomalies parallel to the mid-ocean ridges DEFINITION 32 -caused by reversals in magnetic direction of Earth's dipole field -at times in the past, Earth's magnetic field would switch polarity for no known reason TERM 33 Measurement of Linear magnetic anomalies parallel to the mid-ocean ridges DEFINITION 33 -Everytime a boat would go over a Mid-Ocean ridge with a magnetometer, when it would go over a field that matched the current field, they would add up to a strong magnetic field (darker lines) and when it didn't match, it would subtract from the strength (lighter lines) -This pattern also gives us the rate at which the plates were moving outward -Opening rate =10 cm/yr TERM 34 Strike DEFINITION 34 -angle between surface trace and North -See picture TERM 35 Dip DEFINITION 35 -Angle between fault plane and surface -See picture TERM 46 Type of Faulting when 3 is vertical DEFINITION 46 -Reverse Thrust Fault -See pic TERM 47 Geodesy and types DEFINITION 47 -The measurement of motion on the Earth's surface -Triangulation- measurement of angles between geodetic markers; measure angles between markers placed along fault, then measure change in angles over time -Trilateration-measurement of distances between geodetic markers -Levelling-measurement of elevation difference between geodetic markers TERM 48 H.F. Reid DEFINITION 48 -discovered the Elastic Rebound Theory for Earthquakes by making geodetic measurements before and after the 1906 San Francisco Earthquake TERM 49 Fault Plane Solution DEFINITION 49 -Beach Ball Solution -SEE NOTES -Be able to tell: -which station is closest/farthest from the earthquake -what is the direction from the earthquake to a station? -What is the strike of the faults? -What is the orientation of the principal stresses? TERM 50 P waves DEFINITION 50 -motion is parallel to the ray path -propagate in liquids, solids and gases -compression waves TERM 51 S Waves DEFINITION 51 -motion is perpendicular to the ray path -propagate in solids only TERM 52 First P motion on a vertical seismometer DEFINITION 52 -Up=away from source -Down=toward source TERM 53 San Andreas Fault DEFINITION 53 -Right lateral strike-slip fault -Transform fault linking spreading center beneath the Salton Sea with a spreading center off the Oregon Coast -plate boundary between the Pacific and North American plates -Slip rate=35 mm/year - Age 30 million years (CA coast used to be a subduction zone) TERM 54 Big Bend DEFINITION 54 -North of LA and compression in the LA basin -Blind-thrust faults TERM 55 Volcanoes DEFINITION 55 -mostly occur at plate boundaries-exceptions are hot spots TERM 56 Volcanoes at Convergent Boundaries DEFINITION 56 -andesite magma-contains a lot of silica SiO2 which explains: -gray color -explosive eruptions -steep-sided composite volcanoes TERM 57 Volcanoes at Divergent Boundaries (and at hot-spots) DEFINITION 57 -Basalt magma-contains less silica SiO2 which explains: - black color -quiet eruptions -shallow-sloped shield volcanoes TERM 58 Tsunami DEFINITION 58 -seismic sea wave usually generated by dip-slip faulting on the ocean floor -very long wavelength (~200 km) -very long period (~15 mins) -Velocity=frequency x wavelength, so tsunamis travel about 800 km/hour, the speed of a jet plane TERM 59 Amplitude increases as wave approaches shore because.. DEFINITION 59 the front of wave slows first when it hits shallow water near shore, then the back of the wave catches up, shortening the wavelength but increasing the amplitude -why ordinary sea waves break when they reach shore TERM 60 Amplitude DEFINITION 60 -distance above equilibrium