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Copy of Copy of Chapter 14: The Ocean Floor

group 1
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Kris Kondolf

on 11 February 2013

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Transcript of Copy of Copy of Chapter 14: The Ocean Floor

By Group 1 Chapter 19: The Ocean Floor The Blue Planet
*Nearly 71 percent of Earth’s surface is
covered by the global ocean.
*Oceanography is a science that draws on
the methods and knowledge of geology,
chemistry, physics, and biology to study all
aspects of the world ocean. 19.1 The Vast World Ocean The World Ocean The world ocean can be divided into five main ocean
basins—the Pacific Ocean, the Atlantic Ocean, the
Indian Ocean,Southern Ocean and the Arctic Ocean.

*The Pacific Ocean is the largest and has the greatest depth.
*The Atlantic Ocean is about half the size of the Pacific
and not quite as deep.
*The Indian Ocean, largely a southern hemisphere body,
is slightly smaller than the Atlantic.
*The Arctic Ocean is about 7 percent of the size of the Pacific.
The Southern ocean extends from the coast of Antarctica to 60 degrees South latitude. Divisions of the Global Oceans The topography of the ocean floor is as diverse as that of the continents.

*Bathymetry is the measurement of ocean depths and the charting
of the shape or topography of the ocean floor.
*Today’s technology—particularly sonar, satellites, and submersibles—
allows scientists to study the ocean
floor in a more efficient and precise manner than ever before. Mapping the Ocean Floor The Topography of the Ocean Mapping the Ocean Floor Sonar Methods *Sonar
-Sonar is an acronym for sound navigation and ranging. It is also referred to as echo sounding.*Sonar works by transmitting sound waves toward the ocean bottom.
-Sonar works by transmitting sound waves toward the ocean bottom. Satellites
*Satellites are able to measure small differences by bouncing
microwaves off the ocean surface.
*Using this new technology, scientists have discovered
that the ocean surface is not perfectly flat.
*Differences in the height of the ocean surface are caused by
ocean-floor features. Mapping the Ocean Floor Satellite Methods Submersibles
*Submersibles are small underwater crafts used for deep-sea research.
*Today, many submersibles are unmanned and operated remotely by computers. These remotely operated vehicles (ROVs) can remain underwater for long periods. Mapping the Ocean Floor Mapping the Ocean Floor The 2 major ocean floor ares are the continental margins and the ocean basin floor. Continental Margins *A continental margin is the zone of transition between
a continent and the adjacent ocean basin floor.
*In the Atlantic Ocean, thick layers of undisturbed sediment cover the continental margin. This region has very little volcanic or earthquake activity. Atlantic Continental Margin Continental Margins Continental Shelf
*A continental shelf is the gently sloping submerged surface extending from the shoreline.

*Continental shelves contain important mineral deposits,
large reservoirs of oil and natural gas, and huge sand and
gravel deposits. Continental Margins *A continental slope is the steep gradient that leads to the deep-ocean floor and marks the seaward edge of the continental shelf.*A submarine canyon is the seaward extension of a valley that was cut on the continental shelf during a time when sea level was lower—a canyon carved into the outer continental shelf, slope, and rise by turbidity currents.
*A turbidity current is the downslope movement of dense, sediment-laden water created when sand and mud on the continental shelf and slope are dislodged and thrown into suspension. Continental Slope Submarine Canyons Continental Rise
A continental rise is the gently sloping surface at the base of the continental slope. 14.2 Ocean Floor Features *The ocean basin floor is the area of the deep-ocean floor between the continental margin and the oceanic ridge.
*Deep-Ocean Trenches-Trenches form at the sites of plate convergence where one moving plate descends beneath another and plunges back into the mantle. Ocean Basin Floor Abyssal Plains
-An abyssal plain is a very level area of the deep-ocean floor, usually lying at the foot of the continental rise.
The sediments that make up abyssal plains are carried there by turbidity currents or are deposited as suspended sediment settles out.

The sediments that make up abyssal plains are carried there by turbidity currents or are deposited as suspended sediment settles out.
Seamounts and Guyots-A seamount is an isolated volcanic peak that rises at least 1000 meters above the deep-ocean floor, and a guyot is an eroded, submerged seamount. Ocean Basin Floor Abyssal Plain Cross Section *A mid-ocean ridge is found near the center of most ocean basins. It is an interconnected
system of underwater mountains that have developed on newly formed ocean crust.

Seafloor Spreading
*Seafloor spreading is the process by which plate tectonics produces new oceanic
lithosphere at ocean ridges.
New ocean floor is formed at mid-ocean ridges as magma rises between the diverging
plates and cools. Mid-Ocean Ridges Hydrothermal Vents-Hydrothermal vents form along mid-ocean ridges. These are zones where mineral-rich water, heated by the hot, newly-formed oceanic crust, escapes through cracks in the oceanic crust into surrounding water. Mid-Ocean Ridges Types of Seafloor Sediments:

Ocean-floor sediments can be classified according to their origin into three broad categories: inorganic sediment, biogenic sediment, and sediments that are chemical deposits.

Inorganic Sediment
-Inorganic sediments consist primarily of mineral grains that were eroded from continental rocks and transported to the ocean. 14.3 Seafloor Sediments Hydrothermal Vents
Hydrothermal vents form along mid-ocean ridges.
These are zones where mineral-rich water, heated by the hot, newly-formed
oceanic crust, escapes through cracks in the oceanic crust into surrounding water. Mid-Ocean Ridges Ocean-floor sediments can be classified according to their origin into
three broadcategories:
terrigenous sediment, biogenous sediment, and hydrogenous sediment. Types of Seafloor Sediments Inorganic-Inorganic sediments consist primarily of mineral grains that were eroded from continental rocks and transported to the ocean *Biogenic Sediment
Biogenic sediments consist of shells and skeletons of marine animals and algae. Types of Seafloor Sediments - Calcareous ooze is thick, common biogenous
sediment produced by dissolving calcium carbonate
shells.
- Siliceous ooze is biogenous sediment composed of silica-
based shells of single-celled animals and algae. Types of Seafloor Sediments Biogenous Sediments Energy Resources - Oil and natural gas are the main energy products currently being
obtained from the ocean floor. 14.4 Resources from the Seafloor Gas Hydrates- Gas hydrates are compact chemical structures made of water and natural gas.

Most oceanic gas hydrates are created when bacteria break down organic matter in ocean-floor sediments. Gas Hydrates Other major resources from the ocean floor include sand and gravel, evaporative salts, and manganese nodules. Other Resources Sand and Gravel -The offshore sand-and gravel industry is second in economic value only to the
petroleum industry. Manganese Nodules-Manganese nodules are hard lumps of manganese and other metals (like cobalt, copper, and iron) that precipitate around a small object. Other Resources Evaporative Salts-When seawater evaporates, the salt increases
in concentration until it can no longer remain dissolved.
When the concentration becomes high enough, the salts
precipitate out of solution and form salt deposits.
-The most economically important salt is halite—common table salt. Manganese Nodules -A continental slope is the steep gradient that leads to the
deep-ocean floor and marks the seaward edge of the
continental shelf.
-A submarine canyon is the seaward extension of a valley
that was cut on the continental shelf during a time when
sea level was lower—a canyon carved into the outer continental
shelf, slope, and rise by turbidity currents.
-A turbidity current is the downslope movement of dense,
sediment-laden water created when sand and mud on the
continental shelf and slope are dislodged and thrown
into suspension. Chemical Deposit Sediment
Chemical deposits consists of minerals
that
crystallize directly from ocean water through
various chemical reactions.
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