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Chapter 23 Test Review
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Today, ships use a devise called a precision
depth recorder to determine the distance to
the sea floor.
Deep-sea trenches, continental slopes, and
continental shelves are features commonly
found at active continental margins.
The shelf edge is the boundary between the
continental shelf and the continental slope.
Satellites can obtain information about the sea
floor because the sea surface level varies
slightly with sea-floor depth.
Robert S. Dietz looks on as Robert F. Dill monitors precision depth recorder on the Oceanographer
in 1967 during its around the world cruise. (NOAA Photo Library).
http://oceanexplorer.noaa.gov/history/electronic/1946_1970/media/dietz.html
http://earthnet-geonet.ca/images/glossary/continental_slope.jpg
One method of obtaining a sample of sea-floor
sediment with its layers preserved involves
using a gravity corer.
Passive continental margins are characterized
by the presence of coastal plains.
Suppose sound travels at an average rate of
1500 meters per second through seawater
above a particular location. How deep is the
ocean if a sound pulse takes 10 seconds to
reach the bottom and return to a surface
ship? 7500 meters
The portions of large submarine canyons
that cut through the lower continental
slope are thought to have been carved
out by turbidity currents.
The ultimate source of most of the
material found on the surface of abyssal
plains is sediments carried to the ocean
by continental rivers.
Abyssal hills are commonly found on the
sea floor next to oceanic ridge systems.
Deep-sea trenches occur at convergent plate
boundaries where one tectonic plate is
sinking beneath another.
Where an oceanic plate descends beneath a
continental plate, what features are common
along the edge of the continent?
Earthquakes and volcanoes.
Mid-ocean ridges are undersea mountain
ranges where lithospheric plates are moving
apart and new oceanic crust is being formed.
Segments of mid-ocean ridges are offset relative to each
other by fracture zones.
Sinking volcanic islands and developing coral reefs are
related to the formation of atolls.
Sediments covering the ocean floor are made up of a wide
range of sizes that settle to the sea floor at different
rates.
Sediments made from microscopic shells that settle to the
bottom when the organisms that produced them die are
called biogenous sediments.
As rivers carry continental sediments to
the ocean, the particles most likely to be
deposited on the deep-sea floor are
muds and clays that can be carried
great distances by currents.
As icebergs melt, they release sediments
and pieces of rock that sink to the
ocean floor.
Sediments containing 75 percent of the
ocean’s siliceous sediment are found
near Antarctica.
Types of Ocean Sediments
Ocean bottom sediment map. Lithogenous areas are mauve, biogenous
areas are purple and brown (purple = siliceous ooze, brown = calcareous
ooze), and hydrogenous areas are blue
Terrogenous sediments
Biogenic Shell
Fragments
This diagram shows a passive continental margin and a part
of an ocean basin. Which region is most likely to be
covered with a thick layer of relatively coarse sediments
deposited by turbidity currents? Which region is most likely
to be completely underlain by continental crust? What is the
name of region B? Of region D? (4 points)
The diagram shows a passive continental
margin and a part of an ocean basin. Which
region is most likely to be covered with a
thick layer of relatively coarse sediments
deposited by turbidity currents? Which
region is most likely to be completely
underlain by continental crust? What is the
name of region B? Of region D? (4 points)
Continental shelf
Continental rise
Essay 1:
Compare the type of information obtained with
a precision depth recorder with that obtained
by a gravity corer.
A precision depth recorder produces a
continuous record of seafloor depth under
the ship as it moves over an area.
A gravity corer provides information about the
seafloor at one point only. A gravity corer
provides a vertical sample of the layers of
the seafloor.
Essay 2:
Identify three ways in which the origins of oozes
and manganese nodules are different.
Oozes are the remains of organisms and are
biological in origin; manganese nodules form
as minerals crystallize from seawater and are
inorganic in origin.
The particles that form oozes form primarily in
surface waters, while nodules form on the sea
floor. Oozes form more quickly than nodules.
Oozes form from calcareous or siliceous
material, while nodules form from metallic
minerals.