VOCAB CHAP 3 Flashcards
BATHYMETRY
The measurement of ocean depth.
FATHOM
A unit of depth in the ocean, commonly used in countries using the English system of units. It is equal to 1.83 meters (6 feet).
SOUNDINGS
A measured depth of water beneath a ship.
RELIEF
islands, shallow banks, and deep basins
ECHO SOUNDING
A device that transmits sound from a ship’s hull to the ocean floor where it is reflected back to receivers. The speed of sound in the water is known, so the depth can be determined from the travel time of the sound signal
PRECISION DEPTH RECORDER (PDR)
An early type of sonar device that was developed in the 1950s.
MULTIBEAM ECHO SOUNDERS/SIDE-SCAN SONAR
to make detailed bathymetric maps of a small area of the ocean floor (used to map the seabed)
CONTINENTAL SHELF
A gently sloping depositional surface extending from the low water line to the depth of a marked increase in slope around the margin of a continent or island.
SIDE-SCAN SONAR
A method of mapping the topography of the ocean floor along a strip up to 60 kilometers (37 miles) wide using computers and sonar signals that are directed away from both sides of the survey ship.
SEISMIC REFLECTION PROFILE
A profile view of the structure beneath the sea floor produced by the energy generated from explosions or air guns
SUBMARINE CANYONS
A steep, V-shaped canyon cut into the continental shelf or slope
SHELF BREAK
The depth at which the gentle slope of the continental shelf steepens appreciably. It marks the boundary between the continental shelf and continental rise.
CONTINENTAL SLOPE
A relatively steeply sloping surface lying seaward of the continental shelf.
CONTINENTAL RISE
A gently sloping depositional surface at the base of the continental slope.
TURBIDITE DEPOSITS
A sediment or rock formed from sediment deposited by turbidity currents characterized by both horizontally and vertically graded bedding.
TURBIDITY CURRENTS
Currents that move downslope, eroding the continental margin to enlarge submarine canyons. Deep-sea fans are composed of turbidite deposits, which consists of sequences of graded bedding.
SUBMARINE FANS/DEEP SEA FANS
A large fan-shaped deposit commonly found on the continental rise seawards of such sediment-laden rivers as the Amazon, Indus, or Ganges-Brahmaputra.
ABYSSAL PLAIN
A flat depositional surface extending seaward from the continental rise or oceanic trenches.
OCEAN TRENCHES
deep linear scars in the ocean floor, caused by the collision of two plates along convergent plate margins
FRACTURE ZONE
An extensive linear zone of unusually irregular topography of the ocean floor, characterized by large seamounts, steep-sided or asymmetrical ridges, troughs, or long, steep slopes. Usually represents ancient, inactive transform fault zones.
PACIFIC RING OF FIRE
An extensive zone of volcanic and seismic activity that coincides roughly with the borders of the Pacific Ocean.
MID-OCEAN RIDGE
A linear, volcanic mountain range that extends through all the major oceans, rising 1 to 3 kilometers (0.6 to 2 miles) above the deep-ocean basins. Averaging 1500 kilometers (930 miles) in width, rift valleys are common along the central axis. Source of new oceanic crustal material.
HYDROTHERMAL VENTS
Ocean water that percolates down through fractures in recently formed ocean floor is heated by underlying magma and surfaces again through these vents. They are usually located near the axis of spreading along the mid-ocean ridge.
SEAMOUNTS
An individual volcanic peak extending over 1000 meters (3300 feet) above the surrounding ocean floor
