The world’s tallest waterfall has been discovered, but it’s ‘invisible’ in our eyes

Seeing a waterfall is a spectacle that is difficult to resist. The higher or wider the waterfall, the more magnificent it seems to us. There are some very famous waterfalls, such as the Salto Angel, almost 1000 meters high, or the Victoria Falls with a crest a kilometer and a half long. However, none of these is the largest waterfall in the world: to find it, we have to go below sea level. Yes: the largest waterfall in the world is an underwater waterfall. Let’s explore why!

What is an underwater waterfall and how is it formed?

A waterfall is an area where a watercourse experiences an abrupt, almost vertical interruption in its descent toward the sea. The drop in altitude created due to erosion, tectonic movements, or melting ice contributes to interrupting the flow of the river and therefore generates the waterfall. This is what happens on the surface, in the landscape that we are used to seeing every day.

But what about underwater waterfalls? The explanation can only be different: in many cases, underwater waterfalls are in fact a simple optical effect due to:

  • variations in seafloor depth;
  • sand and mud deposits;
  • particular viewing angles.

There are some such waterfalls that are also very well known, but the phenomenon can also be explained in another way. An underwater waterfall occurs when two bodies of water have different and constantly varying temperatures, densities, and salinities. In this case, they can create a real underwater waterfall, of unimaginable dimensions compared to the waterfalls we are used to on the surface.

A submerged waterfall in Mauritius

Jonpeña22/Wikimedia Commons – CC BY-SA 4.0 DEED

The view is extraordinary and communicates very well the particularity of the Mauritius Islands. Shortly offshore, the seabed suddenly drops hundreds of meters, creating a dark blue hue. Seen from a certain perspective, there appears to be a real underwater waterfall: the water plunges from the surface even lower, disappearing to the bottom. But is this really the case? In reality, the submerged waterfall in Mauritius is more due to sand erosion than water movement. Currents continually erode the coast and shallow seabed, a phenomenon that adds to the island’s volcanic nature and near-black cliff face. However, it is not a real underwater waterfall.

What is the largest waterfall in the world?

The largest waterfall in the world is actually located in the Denmark Strait, which separates Iceland from Greenland. And this time it’s a real underwater waterfall. In this strait, water from the Greenland Sea plunges into the Irminger Sea more than 3 kilometers high and 160 kilometers wide. It is estimated to discharge around 5 million cubic meters of water per second, but why does this phenomenon occur?

The explanation of the largest waterfall in the world is linked to the density of the water, which is determined by its temperature and its degree of salinity. Denser water is heavier than less dense water, and cold water has a higher density than warm water, as does saltier water. When the waters of the Greenland Sea meet those of the Irminger Sea, their density causes them to plunge beneath the warmer, less dense waters, creating the world’s largest waterfall.

An immense waterfall but invisible to our eyes


Technically, the Denmark Strait underwater waterfall might not be the largest in the world. A similar phenomenon is occurring in Antarctica, on the other side of the globe. When seawater begins to freeze and releases the salt it contains, the process makes the underlying water even saltier. As we have seen, saltier water also means denser water, which is then caused to sink to the seafloor with a fall of several kilometers. This slow, invisible waterfall contributes to the thermal regulation of the oceans, regulating the average water temperature and avoiding abrupt climate changes. Of course, unless climate change is already underway, with the risk of destabilizing this process and making these wonderful natural phenomena disappear.

Image preview: Google Maps, Pickpik

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