# Shared Flashcard Set

Oceanography 1
Exam 1
44
Geology
02/03/2016

## Additional Geology Flashcards

Term
 Eratosthenes
Definition
 On June 21 (= summer solstice), midday sun directly over city of Syene (Aswan) On June 21: Angle of sun at midday in Alexandria was 7.2o If the world was flat than there should be no difference in the angle. (500 miles)(360o /7.2o ) = x = 25,000 miles
Term
 Pytheas
Definition
 worked out simple method for determining la)tude: • determine the angle between the horizon and the North Star (Polaris)
Term
 Latitude & longitude
Definition
 Lat across, long up and down. Grid system used to precisely describe locations on the Earth’s surface. Based on angular relationships to Earth’s center. Expressed in degrees (o); each degree is divided into 60 minutes (‘), each minute into 60 seconds (“)
Term
 Latitude
Definition
 • “parallels” = grid lines that are parallel to the Equator  • 0o at Equator, 90o at poles • 0o -90o N = N. Hem. • 0o -90o S = S. Hem. Everywhere on Earth’s surface: 1o lat. = 60 nautical miles, 1’ lat. = 1 nautical mile.
Term
 Longitude
Definition
 • “meridians” = grid lines that intersect at poles • 0o = “PrimeMeridian” (Greenwich, England) • 180o = halfway around Earth • 0o-180o to west of Greenwich = W. Hem. • 0o-180o to east of Greenwich = E. Hem.
Term
 sextant and chronometer
Definition
 sextant is a tool to measure the angle of the sun to the horizon to get lat and chronometer compares your time to Greenwich time. (The difference between your time and GMT) X (15o Longitude per hour) = Your Longitude. If you are ahead of GMT you are in the Eastern Hemisphere (E is for Earlier).
Term
Definition
 determine latitude by measuring the angle of the north star from the horizon. Use southern cross in the southern hemisphere.
Term
 Soundings
Definition
 Weighted lines lowered from ships. Time consuming, relatively few, questionable accuracy
Term
 echo sounding (2D)
Definition
 Sound source & receiver (hydrophone) on hull of ship. High frequency sound waves travel through the water, reflect off the seafloor, and are recorded by the hydrophone. Provide continuous 2-dimensional depth profiles along a ship’s track. d = (v)(t/2)
Term
 multi-beam or side-scan sonar (3D)
Definition
 Like an echo sounder, but it images a 60 km swath of seafloor š Overlapping swaths = complete coverage (3-D)
Term
 Matthew Maury
Definition
 First attempt at a bathymetric map by Matthew Fontaine Maury based on soundings. Showed vast relatively shoal area in Mid-Atlantic.
Term
 Techniques to see the structure of the sub-seafloor
Definition
 Lower frequency energy source (stronger sound source with fewer sound waves per second). Deeper penetration into sedimentary layers and ocean crust
Term
 seismic reflection profiles
Definition
 Sound source and hydrophone towed by ship. 2-D, continuous profile. Lower frequency energy source (stronger sound source with fewer sound waves per second). Deeper penetration into sedimentary layers and ocean crust
Term
 satellite altimetry
Definition
 Precise altimeters (using microwaves) can map the relief of the ocean surface with centimeter-scale resolution š Bathymetric highs and lows on the seafloor, and differences in rock density, cause measureable gravitational distortion of the ocean surface
Term
 bathymetric map
Definition
 depict the topography, or relief of the seafloor; isobaths connect points of equal depth, like the contours lines on topographic maps
Term
 Crust
Definition
 Oceaninc and Continenetal
Term
 Mantle
Definition
 Oceaninc crust, and lava part.
Term
 Moho
Definition
 Thin region between the mantle and crust.
Term
 Lithosphere
Definition
 all crust portions
Term
 Asthenosphere
Definition
 the upper mantle part that is lava right under oceanic crust.
Term
 Oceanic Crust
Definition
 less thick than continental and denser cause primarily basalt. Subducted at trenches during collision.
Term
 Continental Crust
Definition
 thicker and less dense than oceanic cause primarily granite. Preferentially preserved during collision.
Term
 Calculation of crust density
Definition
 Density=mass/volume.
Term
 Isostasy
Definition
 the state of gravitational equilibrium between Earth's crust and mantle such that the crust "floats" at an elevation that depends on its thickness and density of underlying roots of the low density of the mountain.
Term
 continental shelf
Definition
 offshore extension of the continent relatively shallow;
Term
 continental slope
Definition
 underlain by thinned continental crust dissected by numerous submarine canyons
Term
 continental rise
Definition
 - thick accumulation of terrigenous sediments at base of the slope (= deep-sea fans)
Term
 abyssal plains
Definition
 deep, extensive, virtually flat plains
Term
 volcanoes
Definition
 islands, atolls, guyots, seamounts, abyssal hills
Term
 atolls
Definition
 fringed by coral reefs that continue to grow up as it subsides Makes steeps sided pillar.
Term
 guyots
Definition
 – flat topped volcanic peak. Once at surface, but wave-cut then subsiding
Term
 trenches
Definition
 deep, long, narrow, steep-sided troughs seismically active associated with volcanism landward of the trench
Term
Definition
 convection of rising hotter lava in mantle drives upward creating cracks that drive coninents outward from it on both sides.
Term
 Passive margins
Definition
 edge of shelf that is pushing against another due to being side furthest from spreading center.
Term
 active margins
Definition
 edge of shelf that is not getting pushed against another due to being the side closest to the spreading center.
Term
 “Ring of Fire”
Definition
 - the perimeter around the pacific plate that is exerting force almost all the way around resulting in a circle of volcanoes and earthquakes.
Term
 ocean-ocean collision
Definition
 results in island arcs
Term
 ocean-continent collision
Definition
 results in volcanic mountain range near the edge of a continent
Term
 continent-continent collision
Definition
 results in high mountain range since thick buoyant continental lithosphere cannot be subducted.
Term
 Divergent
Definition
 where upwelling Asthenosphere results in melting and new ocean crust (basalt) is formed; the Mid-Atlantic Ridge is a slow spreading center, whereas the East Pacific Rise is a fast spreading center. Spreading centers are characterized by shallow earthquakes. Ocean ridges.
Term
 Transform faults
Definition
 occur at off-sets of oceanic ridges (spreading centers); they represent strike-slip plate boundaries and are characterized by shallow earthquakes.
Term
 magmatic arcs
Definition
 (= volcanoes in the ocean or on land) forms landward of the trench on the overriding plate.
Term
 “hot spots”
Definition
 are volcanoes formed by stationary mantle plumes from deep in the mantle, unrelated to convection in the Asthenosphere (i.e., they are not related to plate tectonic processes such as subduction or seafloor spreading); hot spots produce linear island chains (e.g., Hawaiian Island-Emperor Seamount Chain) .
Term