Oceanography Chapter 3-4 – Flashcards
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Bathymetry
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measures the vertical distance from the ocean surface to mountains, valleys, plains and other sea floor features; measured down from sea level with positive numbers
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Soundings
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First in Mediterranean Sea in 85 B.C.; line with heavy weight (lead line); used for 2000 years; disadvantages: exact position of ship unknown, ship movement, when was the bottom hit, time consuming, sparse single point measurements
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Echo Soundings
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mounted below ship; sends signal 'ping' down to ocean floor; boat records time it takes for echo to return to surface;
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Side-scan sonar
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produces photo like images
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Satellite Altimetry
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measures sea floor features based on gravitational anomalies in sea surface; low areas (trenches) have weaker gravitational pull- sea surface depresses; massive objects (seamounts) have stronger gravitational pull- sea surface bulges; shows higher resolution of sea floor features
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Seismic Reflection Profiles
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to see below ocean floor; produce strong, low frequency sound waves that penetrate into subsurface layers; sound waves reflect (echo) off boundaries between different rock or sediment layers; receiver measures time for sound wave to return to surface
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Continental Margin
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shallow water areas close to shore
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Deep ocean basins
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deep water areas farther from land
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mid ocean ridge
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submarine mountain range
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passive margins
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continental margin classification; not close to any plate boundary; no major tectonic activity
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active margins
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continental margin classification; associated with convergent or transform plate boundaries; much tectonic activity
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passive margin
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continental shelf, continental slope, continental rise, abyssal plain
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active margin
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continental shelf, continental slope, ocean trench, sea mounts
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continental margins
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features include: continental shelf, shelf break, continental slope, continental rise
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continental shelf
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flat zone from shore to shelf break; shallow, low relief, gently sloping; geologically part of continent
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passive margins
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have a wider continental shelf
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continental slope
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where deep ocean basins begin, change in gradient from shelf; greater slope than continental shelf; marked by submarine canyons cut into slope by turbidity currents
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turbidity currents
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underwater avalanches mixed with rocks and other debris; sediment from continental shelf, moves under influence of gravity; sediments deposited at slope base; erode canyons into continental slope
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continental rise
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transition between continental margin and deep ocean floor; turbidite deposits and submarine fans; sediment accumulates in trench along active margins
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deep ocean basin
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features include: abyssal plains, volcanic peaks, ocean trenches, volcanic arcs
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abyssal plains
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flat depositional surfaces extending beyond continental rise; some of the deepest, flattest parts of Earth; suspension settling of fine particles sediments cover ocean crust irregularities; well-develope in Atlantic and Indian Oceans
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mid ocean ridge
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features: longest mountain chain; volcanic, basaltic lava, divergent plate boundary; hydrothermal vents; fracture zones and transform faults
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hydrothermal vents
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sea floor hot springs with three types of vents; when hot sea water mixes with cold, many dissolved chemicals come out of solution or precipitate; unusual biological communities (chemosynthesizmers, worms, clams); minerals depend on temperature
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Warm water vents
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temperatures below 30, colorless; type of hydrothermal vents
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white smokers
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temps from 30-350, barium chloride; type of hydrothermal vents
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black smokers
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temps above 350; metal sulfides; type of hydrothermal vents
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sediment
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particles of organic or inorganic matter that accumulate in a loose, unconsolidated form
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dredge
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method of collecting marine sediments; inefficient, disturbed sediment, could only get surface sediment
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gravity corers
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method of collecting marine sediments; hollow steel tube with heavy weight on top, thrust into sea floor to collect cores (cylinders of sediment and rock), depth limitation
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rotary drilling
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method of collecting marine sediments; integrated ocean drilling program, international ocean discovery program, Joides Resolution drill ship can drill up to 2100 meters into the sea floor
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Paleoceanography
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the study of how the ocean, atmosphere, and land have interacted to produce changes in ocean chemistry, circulation, biology, and climate in the past
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lithogenous
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terrigenous; sediment derived from land through volcanic eruptions or blown dust; come from the land
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biogenous
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derived from the hard parts of organisms
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hydrogenous
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derived from the dissolved materials in water
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cosmogenous
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derived from extraterrestrial sources
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weathering
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agents such as water, temperature extremes, chemical effects that break rocks into smaller pieces in lithogenous sediments
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quartz
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abundant, chemically stable and durable; similar to glass; majority of lithogenous sediments, such as beach sand
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neritic sediment
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shallow water deposits, close to land, deposited quickly, generally coarse grained
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pelagic sediment
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deep ocean basins, typically fine grained, deposited slowly
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beach deposits
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neritic sediment; often quartz, transported by waves crashing
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continental shelf deposits
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neritic sediment; relict sediments- sediments left behind after last ice age
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Turbidite deposits
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neritic sediment; carried by turbidity currents, graded bedding
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glacial deposits
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neritic sediment; high latitudes, currently forming by ice rafting
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biogenous sediment
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begins as the hard parts (shells, bones, teeth) of a living organism- from microscopic algae and protozoans to fish and whales; contributors are mainly algae (sea weed) and protozoans (single celled microscopic animals)
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macroscopic
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type of biogenous sediment; visible to the naked eye, shells, bones, teeth
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microscopic
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most abundant biogenous sediment; tiny shells or tests, biogenic ooze
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calcium carbonate
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forms calcite and aragonite; common chemical compound in biegenous sediment; coccolithophores and foraminifera
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silica
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other common chemical compound of biogenous sediment
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diatoms
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form of silica; microscopic algae, photosythetic - only found in upper, sunlit surface waters; free floating or planktonic (drift with currents); symmetrical
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radiolarians
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form of silica; single cell protozoan (animal); also planktonic, rely on external food sources
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coccolithophores
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single celled, planktonic algae, photosynthesize, produce thin plates that fall and accumulate on sea floor as coccolith-rich ooze; ooze lithifies over time to form chalk
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foraminifera
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single cell protozoan (animal); heterotrophic, planktonic or benthic; different water temperatures affect the chemistry of the shells (historical temp record); contribute to calcareous ooze
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biogenous sediment
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distribution depends on productivity, destruction, dilution
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productivity
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number of organisms present in the surface water above the ocean floor high=high sediment accumulation
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destruction
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occurs when tests dissolve in seawater at depth
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dilution
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occurs when the deposition of other sediment decreases as the percentage of biogenous sediment found in marine deposits
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stromatolites
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lobate structures produced by cyanobacteria in shallow waters; neurotic biogenous deposit
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siliceous ooze
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diatoms, radiolarians; sea water undersaturated with silica so constantly dissolving; siliceous tests must accumulate faster than they can be dissolved; ooze most commonly associated with cool waters with high biological productivity in surface ocean
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calcareous ooze
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warm, shallow ocean saturated with calcium carbonate; cool deep ocean undersaturated with calcium carbonate
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lysocline
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depth at which CaCO3 begins to dissolve rapidly
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calcite compensation depth
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CCD; depth where CaCO3 readily dissolves and is not found in sediments
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manganese nodules
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round lumps of manganese, iron, and other metals; layered structure formed by precipitation around a central nucleation object; found on deep-ocean floor (abyssal plains) far away from continents
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carbonates
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most carbonate deposits are biogenous in origin, but hydrogenous carbonate deposits can precipitate directly from sea water in tropical climates with high CaCO3 concentration
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metal sulfides
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associated with hydrothermal vents and black smokers; contain iron, nickel, copper, zinc, silver and other metals; deposited on sea floor near mid ocean ridges
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evaporites
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form where there are high evaporations rates and restricted open ocean circulation; as water evaporates in these dry areas, remaining seawater becomes saturated with dissolved minerals, which then begin to precipitate and sink
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cosmogenous sediment
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derived from extraterrestrial sources; very insignificant portion of overall sediment on ocean floor; two types macroscopic meteor debris and microscopic spherules
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cosmogenous sediment
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distribution controlled by proximity to sources of lithogenous sediments, productivity of microscopic marine organisms, depth of water, sea floor features
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pelagic
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3/4 ocean floor; dominated by calcareous oozes, clay common in deeper areas of ocean basins
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neritic
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1/4 ocean floor; continental margins
