WHAT IS THE ATLANTIC RIDGE? - GEOGRAPHY - 2025

The Atlantic, Mid- Atlantic or Mid-Atlantic Ridge is a volcanic mountain range that divides the Atlantic Ocean from North to South.

It has a length of about 15,000 kilometers that cover both the North Atlantic, from the north of Iceland, and the South Atlantic (at a point to the East of South South America that is located 7,200 kilometers from said subcontinent). It is part of the oceanic ridge.

The volcanic mountain range is submerged in water, so the ridge causes the surface of the Atlantic Ocean to break into several islands that can be found grouped in the middle of the sea.

Of all the islands that are located from North to South, only those of San Pedro and San Pablo have a volcanic origin, unlike Iceland, Ascensión, Tristán sa Cunha, Santa Elena and Bouvet, which are not.

Extension of the Atlantic Ridge

It should be noted that the extension of the largest part of the Atlantic ridge occupies some 3,000 to 5,000 meters below its surface.

From its seabed there is a long mountain chain whose peaks, sunk in the water, rise to various meters in height ranging between 1,000 and 3,000 meters.

On the other hand, the Atlantic Ridge has an extension that can go wide, that is, it occupies approximately 1,500 kilometers measured from East to West.

It is well known that the Atlantic Ridge has a great cleft, that is to say, a deep valley that runs the entire length of its crest. Its estimated width is around 10 kilometers and its walls are authentic walls that reach a height of up to 3 kilometers.

In short, this valley forms a natural boundary that at the bottom of the Atlantic Ocean divides the two tectonic plates found on Earth. Its widening occurs constantly, at a rate of 3 centimeters a year.

Due to the high volcanic activity that it has within, the area in which the seabed opens tends to be nourished by its rapid rise. In other words, the magma, when it rises, then cools down, and later becomes a new layer that joins the ocean floor.

The Atlantic Ridge has fracture zones. The best known is the Romanche fracture, which runs from East to West. It also has discontinuities whose extension exceeds 100 kilometers in length.

Discovery and research

XIX century

The existence of the Atlantic Ridge was already sensed in the 19th century, but it could not be confirmed until the 20th century. The first clear indication of this was a find that was classified as spectacular.

It is stipulated that everything happened around the year 1853 during work for the installation of a cable across the Atlantic Ocean that would expand international communications. This was inferred three years earlier by the American oceanographer Matthew Fontaine Maury.

As has been said, the transatlantic cable was the starting step for this discovery. In order to get that cable installed correctly, it was necessary to measure the depth of the ocean.

For this, it was necessary to carry out exhaustive surveys. In these, it was noted that in the signals there was clear evidence of an underwater plateau under water, in the middle of the Atlantic Ocean. However, not much attention was paid to this particularity, so it quickly fell into oblivion.

Almost 20 years passed until a British naval expedition, led by the corvette HMS Challenger, gave new light in 1872. The oceanographic mission of the English was checking what had been found in 1853 and found, of course, that the sides of the Ocean Atlantic were shallower than its central zone.

Soundings, however, continued along the entire length of the oceanic line, and this method continued longer in the remainder of the 19th century.

The twentieth century

The 19th century finds, continued by men like the Scottish naturalist Charles Wyville Thomson (1830-1882), were supplemented in 1922 by the German naval expedition in charge of the Meteor ship.

This time the sounding of the Atlantic Ocean was much more methodical. He was not just testing the waters to install telegraph cables, but made a meticulous study of the maritime area using ultrasound instruments.

Later, a team of scientists managed to find the target: a huge mountain range under the sea that crossed the entire Atlantic Ocean, with a meandering shape.

The most peculiar thing was that while the lowest peaks remained imperceptibly submerged in the water, the highest were in front of their eyes: they were the Atlantic islands, such as Tristán da Cunha, Ascensión and the Azores. But that was not even the half of what he was to discover.

Deeper soundings were conducted in other areas of the Atlantic Ocean in those years. Indeed, the newly found mountain range was found to pass through New Zealand and through Africa. This means that the Atlantic Ridge was not satisfied with crossing the Atlantic Ocean, but extended much further, to the Pacific Ocean.

Furthermore, scientists realized that the Transoceanic Ridge was what they had mistakenly taken to be the Central Atlantic Ridge.

In this way, the experts, in addition to making new discoveries, corrected previous ones. From the 1920s through the 1940s, explorers searched the Atlantic with methods already used to find German submarines during World War II.

This method was quite familiar to them and allowed them to correctly interpret the results of their investigations, in which they gave unmistakable signs of novelty.

After this war, the oceanographic and geological works resumed their normal activities. By then scientists knew that there were a number of radical differences between underwater mountain ranges and those on the continent.

The former were a composition of pressed basalt that encompassed its entire structure from head to toe, quite unlike the latter, which had sedimentary rocks in their composition.

It was in the 1950s, and more specifically in 1953, when discoveries were made that can be classified as revolutionary.

The team of North American scientists, led by geologist Bruce Charles Heezen, noted that there were more landforms at the bottom of the Atlantic Ocean than had originally been believed. To their surprise, Heezen's group found that in the center of the Atlantic Ridge there was a very deep ravine.

This finding was key to corroborating what the previous work of Maury, the HMS Challenger team and Thomson had detected in the 19th century.

That ravine was the bottom of the ocean and its sides were nothing but its walls, which were supposedly the slopes of a giant underwater plateau.

This feature, in fact, extended throughout the entire Atlantic ridge and not just a portion of it. For this reason it was that some scientists baptized this area as the Great Cleft of the Globe.

In sum, the Atlantic Ridge was found to be longer than they might have imagined, since it also passed through the Red Sea, made a detour in the coastal region of the Pacific Ocean and passed through California (particularly in its gulf, in the West Coast of the United States).

The scientists did not doubt, of course, that the Great Cleft was some 60,000 kilometers long, but they noted that it was discontinuous, with sections disconnected by seismic and volcanic action.

By the 1960s there were more expeditions, such as the DSDP Project in 1968 and the Mohole Project, which lasted from 1961 to 1966. The latter was discontinued due to economic problems.

In both cases, more was sought than to make a sounding along the Atlantic Ridge (whose length was already well known together with its intense volcanic and seismic activity). Hence, an approach was made in which rock and sediment samples were taken.

Importance of these discoveries

The findings around the Atlantic Ridge did not go unnoticed, even less with the evidence revealed during the 20th century.

In the first place, the relevance of these works lies in the fact that it could be verified beyond any reasonable doubt that the theory of continental drift, postulated by Alfred Wegener, was absolutely valid.

Second, the presence of the Atlantic Ridge further supported the idea that the Earth began in the shape of a supercontinent called Pangea.

Most important features

Geological features

After studies carried out for more than a century, it has been found that the Atlantic Ridge basically consists of a very deep valley whose shape is sinusoidal.

That is, a long serpentine line that, as noted above, is interrupted in several of its sections due to the intervention of volcanoes and the underwater earthquakes so frequent in that part of the Earth. This line leaves a clear separation in the tectonic layers that are located in the continents that it crosses.

Likewise, it is worth remembering that the terrain of the Atlantic Ridge is formed by hot magma that tries to rise to the surface, but runs into ocean waters.

This causes it to end up cooling and causing a wall of hardened lava to emerge from the underwater volcanic eruption, which becomes the new layer of soil on the seabed. Every year new centimeters of geological plates are added, the thickness of which is constantly increasing.

In addition, the Atlantic Ridge is subdivided into two branches; a northern branch, which is the North Atlantic ridge, and a southern branch, which is the South Atlantic ridge.

In the latter there is a kind of maritime trench, or rather a break, a fracture known as that of Romanche and which sinks to 7,758 meters. It is, therefore, one of the deepest underwater sites in the Atlantic Ocean.

Geographic characteristics

The Atlantic Ridge begins its journey in Iceland and ends in the South Atlantic Ocean. It makes a link with South Africa through the Cape of Good Hope until it passes through the ridge of the Indian Ocean.

From there it passes to the South of Australia through the ridge of the Pacific Ocean, which is extended throughout its southern and eastern zone until it reaches the territory of Mexico, where it touches the western coast of the United States, in California.

There are secondary ridges to the Atlantic, which in turn can be transversal or parallel. Among them are the Hawaii Ridge, the Pacific Ridge and the Kerguelen Ridge.

Today, the ridges that maintain their tectonic activity occupy surfaces that are directly proportional to the continents with which they border.

In addition, along the route of the Atlantic Ridge there are many islands and archipelagos of volcanic origin, in total there are nine islands that are located in the middle of the Atlantic Ridge. On the North Atlantic Ridge are Iceland, San Pedro, the Azores and Jan Mayen.

For its part, the South Atlantic Ridge is made up of the islands of Bouvet, Tristán da Cunha, Gough, Santa Elena and Ascensión. In the particular case of Iceland, the Atlantic ridge passes exactly in the middle, so that it literally divides it in half.

It is worth highlighting a particularity of the Atlantic ridge that serves as evidence for continental drift and consequently for plate tectonics.

The fact is simple but momentous: the Romanche fracture, mentioned above, draws an imaginary horizontal line through the Equator. But what is surprising is not that, but rather that the edges of the Gulf of Guinea and the northeast coast of Brazil fit together and indicate that Africa and America were continents that were once united.

References

1. Mgar: History, Navigation (No year). Seabed 2; Atlantic Ridge. Canary islands spain. Recovered from mgar.net.
2. Burke, K. (1976). "Development of recording associated with the initial ruptures of the Atlantic Ocean". Tectonophysics, 36 (1-3), pp. 93–112.
3. Encyclopædia Britannica (2010). Mid-Atlantic Ridge. London, United Kingdom. Recovered from britannica.com.
4. Ewing, WM; Dorman, HJ et al (1953). "Exploration of the northwest Atlantic mid-ocean canyon." Bulletin of the Geological Society of America, 64, pp. 865-868.
5. Geological Society of London (2017). Mid-Atlantic Ridge. London, UK: GSL. Recovered from geolsoc.org.uk.
6. Spencer, Edgar W. (1977). Introduction to the Structure of the Earth, 2nd edition. Tokyo: McGraw-Hill.
7. UNESCO (2017). The Mid-Atlantic Ridge. Paris, France: UNESCO World Heritage Center. Recovered from whc.unesco.org.
8. US Geological Survey (2014). Understanding plate motions. Virginia, United States: USGS. Recovered from pubs.usgs.gov.