Oceanography 3

Bathymetry
The measurement of ocean depths and the charting of the shape, or topography of the ocean floor. (It involves measuring the vertical distance from the ocean surface down to the mountains, valleys, and plains of the sea floor.
Soundings
a measurement of the depth of the ocean.
Fathom
the standard unit of ocean depth, it is equal to 1.8 meters (6 feet).
Echo Sounder
it sends a sound signal (called a ping) from the ship downward into the ocean, where it produces echoes when it bounces off any density difference.
Multibeam Echo Sounder
Use multiple frequencies of sound simultaneously. Made it possible for a survey ship to map the features of the ocean floor along a strip up to 37 miles wide.
Seismic Reflection Profile
by using strong low-frequency sounds produced by explosions or air guns. These sounds penetrate beneath the sea floor and reflect off the boundaries between different rock or sediment layers.
Continental Shelf
a generally flat zone extending from the shore beneath the ocean surface to a point at which a marked increase in slope angle occurs. Usually flat and relatively featureless because of marine sediment deposits but can contain coastal islands, reefs, and raised banks.
Shelf Break
the point at which the marked increase in slope angle occurs in a continental shelf.
Continental Slope
lies beyond the shelf break and is where the deep-ocean basins begin. The total relief in this region is similar to that found in mountain ranges on the continents.
Submarine Canyon
narrow but deep submarine valleys that are V-shaped in profile view and branches or tributaries with steep to overhanging walls. They resemble canyons formed on land that are carved by rivers and can be quite large.
Turbidity Current
underwater avalanches of muddy water mixed with rocks and other debris.
Continental Rise
a transition zone between the continental margin and the deep-ocean floor comprised of a huge submerged pile of debris.
Deep-Sea Fan
the deposits at the mouths of submarine canyons, as viewed from above, are fan, lobate or apron shaped. They create the continental rise when they merge together along the base of the continental slope.
Abyssal Plains
flat depositional surfaces with slopes of less than a fraction of a degree that cover extensive portions of the deep-ocean basins. They extend from the base of the continental rise into the deep-ocean basins and are some of the deepest (and flattest) regions on Earth.
Abyssal Hills
Volcanic features on the ocean floor that are less than 1000 meters (0.6 mile) tall – the minimum height of a seamount.
Pacific Ring of Fire
it occurs along the margins of the Pacific Ocean. It is home to the majority of Earth’s active volcanoes and large earthquakes because of the prevalence of convergent plate boundaries along the Pacific Rim.
Hydrothermal Vents
sea floor hot springs created when cold seawater seeps down along cracks and fractures in the ocean crust and approaches an underground magma chamber. The water picks up heat and dissolved substances and then works its way back toward the surface through a complex plumbing system, exiting through the sea floor.
Passive margins
are embedded within the interior of lithospheric plates and are therefore not in close proximity to any plate boundaries
Active margins
are associated with lithospheric plate boundaries and are marked by a high degree of tectonic activity. There are two types of active margins: Convergent active margins and Transform active margins.
Passive Continental Margins
Very far away from plate boundaries, no active volcanos they are wider than active continental margins. Passive margins usually lack major tectonic activity (such as large earthquakes, eruptive volcanoes, and mountains). The East Coast of the USA is an example of a passive continental margin. Usually produced by rifting of continental landmasses and continued sea floor spreading over geologic time. They include a continental shelf, the continental slope, and the continental rise that extends toward the deep-ocean basins.
Convergent Active Continental Margins
Features include an onshore volcanic arc shaped row of active volcanos, then a narrow shelf, a steep slope, and an offshore trench that delineates the plate boundary. Western South America where the Nazca Plate is being subducted is an example.
Transform Active Margins
Are less common and are associated with transform plate boundaries. Offshore faults usually parallel the main transform plate boundary fault and create linear islands, banks (shallowly submerged areas), and deep basins close to shore. Costal California along the San Andreas Fault is an example.
Warm-water vents
have water temperatures below 30 C (86F) and generally emit water that is clear in color.
White smokers
have water temperatures from 30C to 350C (86F to 662F) and emit water that is white because of the presence of various light-colored compounds, including barium sulfide.
Black smokers
have water temperatures above 350C (662F) and emit water that is black because of the presence of dark-colored metal sulfides, including iron, nickel, copper, and zinc.