The ocean floor, or seabed, is the solid surface of the Earth beneath the ocean. It has mountain ranges, deep trenches, flat plains and a sloping edge where it meets the continents.
Key takeaways
- The ocean floor is not one flat bowl: it runs from a shallow shelf at the coast, down a slope, across vast plains and into trenches.
- In the GEBCO_2026 grid the ocean averages 4,085 m deep, and the deepest point is 10,927 m down at Challenger Deep.
- About 71% of the Earth's surface in our grid lies below sea level.
- Only part of the seabed has been mapped in fine detail, so much of our map is filled in from satellite estimates.
How the ocean floor is laid out
The ocean floor is the solid ground under the water. Seen as a cross-section from a coast out to the middle of an ocean, it usually follows the same order [2][3].
- The continental shelf. A gently sloping, shallow ledge that is really the edge of the continent, flooded by the sea.
- The continental slope. A steeper drop from the edge of the shelf towards the deep ocean.
- The continental rise. A gentler apron of sediment at the foot of the slope.
- The abyssal plain. A vast, flat expanse of deep seabed, covered in fine sediment, with low abyssal hills poking through.
- Ridges and trenches. Long mountain chains run through the middle of the oceans where new crust forms, and narrow trenches plunge down where old crust sinks back into the Earth.
Not every coast has every step. Where one tectonic plate dives under another, the shelf can be almost missing and a trench sits close to land [2]. This site draws the seabed as shaded relief coloured by depth, so you can see these shapes by eye. It does not draw layers for crust type, sediment or plate boundaries.
For the headline numbers, the depth colours and what the ocean covers, see how deep the ocean is on the homepage. This page is about the shape of the ground itself.
An example from our data
The GEBCO_2026 grid is released at 15 arc-seconds spacing, and about 71% of the surface it covers is below sea level, an area of 362 million km². The land is 147.9 million km².
The range between the highest and lowest points is huge. The highest cell in the grid is 8,627 m, and the deepest point is 10,927 m, at Challenger Deep in the Mariana Trench. If the highest ground were placed in the deepest point, its top would still be 2,300 m under water.
You can see the whole layout in a single ocean. The Atlantic Ocean has a mean depth of 3,883 m, with 5.1% of it shallower than 200 m. The Pacific Ocean has a mean depth of 4,315 m, but only 0.7% is that shallow. The Pacific is mostly deep plain and trench, with very little shelf.
The thing people get wrong
Many people picture the ocean floor as a smooth bowl that gets steadily deeper from the beach. In fact most of the way across, the seabed is a broad, nearly level plain, and the steep part is a narrow band near the edge of the continents. The mountain ranges and trenches are more dramatic than anything on the plains.
A second mistake is to think we have photographed or surveyed all of it. Most of the seabed has only been measured at low resolution. The grid fills gaps with depths estimated from satellite measurements of the sea surface, so small features on the open ocean floor can be missing. NOAA reports that only about 26 percent of the seafloor had been mapped in high resolution as of June 2024 [4]. Our accuracy notes explain what that means for the map.
Frequently asked questions
Is the ocean floor flat?
No. It has long mountain ranges, deep trenches, volcanoes and huge flat plains. The plains are some of the flattest places on Earth, but they sit between much rougher ground.
How deep is the average ocean floor?
In our grid the five oceans average 4,085 m, weighted by area. The deepest point is 10,927 m.
Sources
- GEBCO_2026 Grid, GEBCO.
- Continental shelf, Wikipedia.
- Abyssal plain, Wikipedia.
- How deep is the ocean?, NOAA Ocean Exploration.
- Every figure from our own map is worked out from the datasets on the data sources page (checked against GEBCO_2026 grid).