[Geography Notes] on Oceanic Ridge Pdf for Exam

Oceanic ridge is a continuous submarine chain of mountains that extends roughly 80,000 km (that is 50,000 miles) among all the oceans present in the world. In the ocean basin, these ocean ridges are the largest features. Geographically speaking, these oceanic ridges are the most distinct and prominent feature on the surface of the earth after the continents and oceans being the prominent ones. 

Previously these features were also referred to as the mid-ocean ridges. While the largest ocean ridge, the East Pacific Rise is quite a distance from a mid-ocean location, hence, we can say that the generalization is not exactly correct. Further, students must not confuse these oceanic ridges with aseismic ridges, which originated apart from these.  

Mid Ocean Range

A mid-ocean ridge also known as the mid-oceanic ridge is an underwater mountain range, which is formed by the action of plate tectonics. There is uplifting of the ocean floor, which is caused due to the convection currents as it rises in the mantle which is beneath the oceanic crust and here it creates magma. The creation of magma is done where the two tectonic plates meet at a divergent boundary.

These mid-ocean ridges of the world are all connected and they form a single global mid-oceanic ridge system which is a part of every ocean that makes up the mid-oceanic ridge system. Here the longest mountain range in the world is about 60,000 km in length.

There are two processes involved in this, one is ridge-push and the other is slab-pull, they are responsible for the spreading seen at the mid-ocean ridges, while there is some uncertainty about the fact which is dominant.

Mid Atlantic Ridge

The Mid-Atlantic Ridge abbreviated as MAR is the mid-oceanic ridge which is divergent or is constructive with a plate boundary that is located along the Atlantic Ocean floor. Also, this serves to be the longest mountain range in the world. The Mid-Atlantic Ridge separates North America from the Eurasian and African Plate; this happens in the North Atlantic. Also, this ridge separates North America from Azores Triple Junction. While, in the South of Atlantic, the ridge separates the African and the South American plates. The ridge further extends from a place in the Gakkel Ridge which is called the Mid-Arctic Ridge to the northeast in Greenland, proceeding southward to Bouvet Triple Junction in the Southern part of the Atlantic. 

We know that the Mid-Atlantic Ridge is majorly an underwater feature, while portions of it have elevation to the extent above the sea level, for example in Iceland. 

Submarine Ridge

Submarine Ridge is quite elongated and steep-sided elevation of the ocean and the sea floors. The Submarine ridges extend up to hundreds and thousands of kilometers, lengthwise and the width is about several hundred km. Here the peaks often rise above sea level to form many such islands. 

In the submarine continental margins, the submarine ridges are very rare, while their structure being analogous to the structure of those of the mountains which are located on the adjacent parts of these continents. In the transition zone, the submarine ridges appear mainly like the island arcs.

On the ocean floor, the submarine ridges may be block, or block-folding, or like the volcanic ridges.  The mid-ocean ridges are the largest submarine ridge. 

Indian Ocean Ridge

Talking about the Indian Ocean Ridge, the Carlsberg Ridge which is also a submarine ridge of the Arabian Sea and the Indian Ocean is a prominent feature. This ridge is a portion of the Mid-Indian Ridge and this extends from the vicinity of Rodrigues Island to the Gulf of Aden, basically, this means northwest to southeast. This ridge separates the Arabian Sea located in the northeast from the Somali Basin in the southwest.

East Pacific Rise

The East Pacific Rise is also a mid-oceanic ridge which has a divergent tectonic plate with a boundary that is located along the Pacific Ocean floor. This separates the Pacific Plate in the west from the North American Plate, from the Rivera Plate, from the Cocos Plate, the Nazca Plate and also from the Antarctic Plate. This runs southward from the Gulf of California which is in the Salton Sea basin, South California to a point near 55° S, 130° W, then it joins the Pacific-Antarctic ridge.