Ocean Floor Topography

Prof. Liwayway Memije-Cruz

Ocean Floor Topography the study of numerous landforms that exist

on or below the earth.refers to the different forms in which the

ocean floor bottom can existis similar to the ground topography with

features such as valleys, mountains, and plateaus.

it starts with the Outer Continental Shelf followed by the Continental Slopes, and subsequently the Ocean Floor.

Passive Continental Margin Continental Margin – is the boundary

between the earth and the ocean which is consists of the Outer Continental Shelf followed by the Continental Slopes. The thick and heavy continental stonework is replaced by a thin basalt layer.

The Outer Continental Shelf starts as the water begins. This zone is shallow, slopes progressively, and normally holds water that is not very deep. The Continental Shelf width changes significantly depending on the locality, ranging from a few kilometers to hundreds of kilometers. As the Continental Shelf is crossed, the ocean floor descends steeply. These sharply sloping sections are known as the Continental Slopes. They identify the border between the granite of the continent, and the basaltic crust of the ocean. This is the passive continental margin

Active continental marginCharacteriz

ed by the subduction of an oceanic lithosphere plate beneath a continental plate

Oceanic DivisionsDeep valleys have been

observed in the Continental Slopes which have been created due to the earthquakes, or have been eroded by violent ocean currents.

The divisions of the ocean water according to depth are known as Abyssal Zones. Each layer has its own characteristic features of pressure, temperature, salinity and biodiversity. The deepest oceanic zone is the hadalpelagic zone that lies between 6,000–11,000 meters.

Ocean basins

Submarine canyon any of a class of narrow steep-sided

valleys that cut into continental slopes and continental rises

originate either within continental slopes or on a continental shelf

rare on continental margins that have extremely steep continental slopes or escarpments. Submarine canyons are so called because they resemble canyons made by rivers on land.

occur along the slopes of the Hawaiian Islands and possibly certain other ocean islands. The majority of these V-shaped depressions have steep, rocky walls thousands of meters high.

Ocean currents The rotation of the earth prevailing air currents and variation in water

temperature give rise to ocean currents and surface drifts that tend to move parallel to the equator.  But,  land masses intervene and change the movement of the water in the world’s great oceans – the Atlantic, the Pacific and Indian oceans.  Two circular water movements called gyres control these oceans.  Currents in the gyre move clockwise in the Northern Hemisphere while current in the Southern Hemisphere move counter clockwise. The two gyres are separated by an equatorial countercurrent, which carries water away from the Western boundaries of the ocean basins.  Ocean currents influence the physical condition characteristics of diverse ecosystems.

Coriolis EffectThe apparent

deflection of objects (airplanes, wind, missiles and ocean currents) moving in straight path relative to the earth’s surface.

A pseudo force resulting from the Earth’s rotation from west to east about its axis

Tidal currentsHorizontal movements

of water that accompany the rise and fall of tides

Tides are the daily rise and fall in the elevation of the ocean surface at a specific location

Tides are caused by the attraction of the Moon by the Sun

Ocean wavesWaves of oscillation:

waves formed as water move in circular orbits

Waves of translation: turbulent advance of water near the shore as waves of oscillation breaks and form surf.

Ocean wave can cause erosion due to wave impact, pressure and abrasionBeach drift – sideways

pulling of sandLongshore current or drift

– sands and gravels are transported along a coast at an angle to the shoreline