Oceans

Oceans

The Oceans

• The worlds oceans can be divided into five primary bodies.

• Pacific• Atlantic• Indian • Arctic• Southern

Oceanography

• also called oceanology or marine science, is the branch of Earth science that studies the ocean.

• Oceanography is an interdisciplinary science that draws on geology, chemistry, physics, and biology to study all aspects of the worlds oceans.

• Almost 71% of the Earth’s surface is covered with water

Ocean Floor

The Ocean Floor…

Deep sea floor, at depths

below 4000 meters,accounts for 30% of

theearth’s surface

Dark, deep, hot vents ofboiling water,

dangerousgases..... And miles of

flat abyss..

• The ocean floor is nearly as varied as the land surface

• Marked with distinctive features such as plateaus, trenches, mountain ranges, and volcanic peaks

Bathymetry• A sound (ping) is emitted and while

traveling through water, will reflect off of any solid surface it encounters

• By measuring the time it takes for the ping to travel and be reflected, while noting the speed of sound in water (~1,500 meters per second), a picture of the ocean can be derived

1.High-resolution images can be obtainedby using hull-mounted sound sources that send out pings in a fan shape swath2. The resulting reflections are then

recorded through a set of receivers3. Can acquire a swath tens of kilometerswide and depths can be distinguished upto a meter

Bathymetry:

Ocean Floor Provinces

• Oceanographers have delineated three primary oceanographic units (provinces)

1) Continental margins2) Deep-ocean basins3) Mid-ocean ridge

Continental Margins

• The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope followed by the flatter continental rise. Sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope, called the continental rise

Key components of the continentalmargin

• Continental shelf• shallow, submerged edge of the continent.• A gently sloping submerged surface• extending from the shore to the deep

ocean basin• Underlain by continental crust and

recognized as a flooded extension of a continent

• Varies in width • From a few miles to ~900 miles wide• Average ~50 miles

• is the extended perimeter of each continent and associated coastal plain, and was part of the continent during the glacial periods, but is undersea during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs.

• the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores of a particular country to which it belongs. Such shores are also known as Territorial waters.

Shelf break

• abrupt transition from continental shelf to the continental slope.

Continental slope

• the transition between the continental shelf and the deep-ocean floor.

• A continental slope is typically about 20 km (12.4 mi) wide, consists of mud and silts, and is often crosscut by submarine canyons.

•  The world’s combined continental slope has a total length of approximately 300,000 km (200,000 miles) and descends at an average angle in excess of 4° from the shelf break at the edge of the continental shelf to the beginning of the ocean basins at depths of 100 to 3,200 metres (330 to 10,500 feet).

Continental rise

• accumulated sediment found at the base of the continental slope.

• Sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope

• Extending as far as 500 km from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope.

• the continental rise's gradient is intermediate between the slope and the shelf, on the order of 0.5-1°.

Submarine Canyons

• Formed by water erosion and / or turbidity currents.

•  a steep-sided valley on the sea floor of the continental slope

• Canyons cutting the continental slopes have been found at depths greater than 2 km below sea level. 

Two primary types of continental margins

• Active• Occur where oceanic crust is being sub

ducted beneath the edge of a continent.• Associated with earthquakes and

volcanic activity• Characterized by a narrow band of

highly deformed sediment• Common around the Pacific Rim• Typically parallel to ocean trenches

Passive

• Found along most coastal areas bordering the Atlantic Ocean

• Not associated with any plate boundary

• Little to no earthquake and volcanic activity

• Characterized by weathered materials deposited by rivers to form a thick, broad wedge of relatively undisturbed sediment