Unit 6.1

North Hemisphere is refer to as the

Land Hemisphere

South Hemisphere is refer to as the

Water hemisphere

• The south is covered by less continental landmasses

Pacific Ocean

Major ocean basin

• Largest and has the greatest depth

Atlantic Ocean

Major Ocean Basin

• About half the size of the Pacific and not quite as deep

Indian Ocean

Major Ocean Basin

• Slightly smaller than the Atlantic, largely a southern hemisphere body

Arctic Ocean

Major Ocean Basin

• About 7 percent the size of the pacific and a little more than one quarter as deep as the rest of the oceans

Salinity

The total AMOUNT OF SOLID MATERIAL DISSOLVED IN THE water

Dissolved Substances is expressed in

parts per thousand

avg salinity in the ocean

3.5 per cent

sources of sea salts

• Chemical weathering of rocks on continents is one source

• Other is through volcanic eruptions in a process called outgassing

outgassing

refers to the release of gases from within the Earth’s interior through volcanic vents, cracks, or eruptions.

processes the affect seawater surface salinity

Freshwater in precipitation, runoff,

• Icebergs melting

• Sea-Ice melting (Reduces salntiy)

what’s in the 3 layer structure in the open ocean

• Shallow surface mixed zone - 2%

• Transition Zone (Thermocline or Halocline) - 18%

• Deep zone - 80%

Thermocline

A layer of rapid temp change below the zone of mixing

Halocline

A zone of rapidly changing salinity

the densest seawater are

very cold and very salty (high salinity)

Bathymetry

A research field that involves the measurement of ocean depths and the charting of the shape (topography) of the ocean floor

Echo Sounder / Sonar

invented in the 1920s

• and was the primary instrument for measuring depth. It operates by reflecting sound waves from the ocean floor to determine depth

Multibeam Sonar

Employs an array of sound sources and listening devices. Obtains a profile of a narrow strip of the seafloor.

what are the 3 major tropographical features of the ocean floor

-Continental margins

• Ocean basin floor

• Oceanic (mid-Ocean) ridge)

what are the 2 types of Continental margins

Passive and Active

PAssive continental margins

Type of continental margins

• most coastal areas surround the Atlantic ocean

• little volcanism and earthquakes

• contain continental shelf and slope

Continental margin is like the area wher the continent touches the ocean basin

Continent Shelf

• he shallow, gently sloping area that extends from the shore to the edge of the shelf.

• It's still part of the continent and is often rich in marine life, oil, and gas.

• Example: The Gulf of Mexico has a wide continental shelf.

Continental Slope

• Begins at the edge of the continental shelf and drops steeply down to the deep ocean floor.

• It marks the true boundary between continental and oceanic crust.

Continental Rise

• A gentle incline found at the bottom of the continental slope.

• Made of sediments that have tumbled down from the shelf and slope.

• Leads to the deep ocean floor (called the abyssal plain).

Active Continental Margins

• Narrow or almost no continental shelf

• Steep continental slope

• Trenches may form instead of a rise

• Frequent earthquakes, volcanoes, and subduction

Located at a plate boundary, usually a convergent boundary (or transform)

Passive vs Active continental margisn

Feature	Passive Margin	Active Margin
Plate boundary nearby?	❌ No	✅ Yes
Tectonic activity	Low	High (earthquakes, volcanoes)
Shelf width	Wide	Narrow or none
Subduction zone	❌ Absent	✅ Present
Example	East coast of U.S.	West coast of South America

Submarine Canyons

Valleys that are cut into the continental slope

Turbidity currents

Density currents that originate from sediment-laden coastal waterways

-May produce submarine canyons and turbidities

Turbidities

Graded beds

Deep-ocean trenches

are long, relatively narrow features that are the deepest parts of the ocean

• Mostly located in Pacific Ocean

• Sites where moving lithospheric plate plunge into the mantle, act as sediment trap

• Geologically unstable

• Associated with volcanic activity and can form volcanic island arcs and continental volcanic arcs

Abyssal Plains

These are likely the most level places on Earth and are the sites of think accumulations of sediments

• Extensive in the Atlantic ocean where passive continental mergns dominate

seamounts

isolated volcanic arcs

• Could form near oceanic ridges

Guyot / Tablemounts

Seamounts may emerge as an island, but many sink and form flat-topped features

Atolls

Coral reefs surrounding a lagoon

• Coral reefs need warm clear shallow sunlit water.

Mid-ocean ridges

characterized by an elevated position, heat flows, and rift zones located at the credit the ridge

• Involve extensive faulting and numerous volcanic structures that have developed on newly formed crust

• 620-2500 miles wide, 8200 to 9800 feet above the floor, and extends 44000 miles

• Interconnected ridge system that covers 23% of Earth surface and winds through all of the major ocean basins

most common sediment on the deep-ocean floor

Mud

Terrigenous sediment

Type of seafloor sediment

• every part of the ocean receives some

• Material weathered from continental rocks

• Fine particles remain suspended for a long time

• Oxidation of iron often produces red and brown colored sediments

Biogenous sediment

Type of seafloor sediment

• Shells and skeletons of marine animals and plants (tests)

• Most common are calcareous oozes produced from microscopic organisms that live in warm surface water

• Siliceous oozes composed of tests of diatoms and radiolarians

• Phosphate rich materials derived from the bones, teeth, and scales of fish and other marine organisms,

Hydrogenous sediment

• Minerals that crystallize directly from seawater

• Most common types include Manganese nodules, calcium carbonates, metal sulfies, and evaporites

Cosmogenous sediment

-Come from space

-Composed of large amounts of metals