An oceanic plateau is a large, relatively flat area of the seabed that stands higher than the ocean floor around it, with one or more steep sides. Some are built from huge volcanic outpourings, and others are slivers of continent left in the sea.
Key takeaways
- An oceanic plateau is a large, relatively flat elevation higher than the surrounding relief, with one or more relatively steep sides [1].
- Some plateaus are made of vast volcanic outpourings, and others are made of rifted continental crust [1].
- Our list has 25 named plateaus, from the shallow Mascarene Plateau (280 m at its listed point) to the Ontong Java Plateau (2,948 m).
- The Kerguelen Plateau is a good example of a plateau that mixes both origins [1].
How an oceanic plateau works
Most of the open ocean floor is a deep, fairly flat plain with ridges, trenches and seamounts scattered over it. An oceanic plateau is a different shape: a large, relatively flat elevation, higher than the seafloor around it, with one or more steep sides [1].
Plateaus can be built in two main ways [1]:
- Volcanic plateaus are made by enormous eruptions, equivalent to the flood basalts found on land. They often rise 2 to 3 kilometres above the surrounding ocean floor and are more buoyant than normal oceanic crust. That buoyancy helps them resist being pulled down at subduction zones, so some end up attached to continents.
- Continental plateaus are made of rifted continental crust, a piece of a continent that split away and now sits in the ocean.
Some plateaus have mixed origins. Wikipedia lists the Lord Howe Rise as continental crust, and parts of Kerguelen as well [1]. Plateaus also often link to hotspots and mantle plumes, the long-lasting hot spots deep below the plates [1].
Size is a clue to scale. Wikipedia counts 184 oceanic plateaus worldwide, covering about 5 per cent of the oceans [1]. The three largest are the Caribbean, Ontong Java and Mid-Pacific Mountains [1]. A plateau is also different from the continental shelf, which is the part of a continent submerged under relatively shallow water [2].
The homepage explains how deep the ocean is and how to read the map's colours. This page is about the plateau shape itself.
An example from our data
Our list has 25 named plateaus. They span a wide range of depths, because the depth on each page is the deepest grid cell near the listed point.
The Kerguelen Plateau, in the southern Indian Ocean, reads 634 m at its listed point, about 194 km from French Southern and Antarctic Lands. The Ontong Java Plateau reads 2,948 m, while the Mascarene Plateau reads 280 m and the Blake Plateau 776 m.
Those are very different depths for the same type of feature, which shows that "plateau" describes a shape, not a depth. Our map labels the Lord Howe Rise as a ridge, not a plateau, so the label depends on the source data.
You can see how a shallow plateau behaves as the sea falls. Open the Ice Age slider and drop the level. The slider is a simple model that lowers the sea evenly on today's seabed, so it ignores ice sheets and changes to the crust, but it is enough to see which high ground comes close to the surface. See also the sea-level steps.
The thing people get wrong
People often assume the deep sea is a bowl with a flat bottom that gets deeper toward the middle. In reality it has great plateaus that rise thousands of metres above the basins around them. Another mistake is to treat every plateau as volcanic. Some are slivers of continents that broke away [1].
Oceanic plateau vs continental shelf
| Oceanic plateau | Continental shelf | |
|---|---|---|
| Where | In the ocean, away from continental margins or at their edge | The submerged edge of a continent, in shallow water [2] |
| Built from | Volcanic outpourings or rifted continental crust [1] | The submerged edge of a continent [2] |
| Example | Kerguelen Plateau | The North Sea floor |
Frequently asked questions
How is an oceanic plateau different from the continental shelf?
A continental shelf is the shallow edge of a continent. An oceanic plateau is a raised block that stands away from the continents, or beyond the shelf edge, in deeper water.
Could an oceanic plateau ever become dry land?
A few reach shallow depths, but dry land would need the sea to fall a long way. You can test how much land appears at different levels with the drain slider, which is a simple model only.
Sources
- Oceanic plateau, Wikipedia.
- Continental shelf, Wikipedia.
- Every figure from our own map is worked out from the datasets on the data sources page (checked against GEBCO_2026 grid).