The Black Sea holds the largest anoxic (oxygen-free) water body on Earth - about 90 percent of its volume sits below a thin oxygen-rich surface layer, with no life beyond microbes down to a floor 2,212 m deep. Toggle the oxic/anoxic bands to see where the oxygen runs out.
Published figures: surface area about 436,400 sq km; maximum depth about 2,212 m; the oxygen-rich surface layer is only about 150-200 m thick, so roughly 90 percent of the sea's volume is anoxic below that boundary (the chemocline).
Drag to orbit and scroll or pinch to zoom. Everything renders on your device with WebGL.
Black Sea 3D Explorer
This browser explorer shows the Black Sea in cross-section: a thin oxygen-rich surface layer sitting on top of the largest anoxic (oxygen-free) water body on Earth, plus the shallow northwest continental shelf that breaks the pattern near Ukraine and Crimea.
Roughly 90 percent of the Black Sea's volume lies below the chemocline - the boundary, only about 150-200 m down, where dissolved oxygen runs out and hydrogen-sulfide-rich anoxic water takes over all the way to the 2,212 m floor. That permanent stratification (the water column almost never mixes top to bottom) is also why ancient shipwrecks are found remarkably preserved in the deep anoxic layer. At about 436,400 sq km, the sea is bordered by Turkey, Bulgaria, Romania, Ukraine, Russia, and Georgia, and it drains to the Mediterranean through the Bosphorus Strait, the Sea of Marmara, and the Dardanelles.
- Toggle the oxic/anoxic bands to see the thin oxygen-rich layer versus the vast oxygen-free depths
- Toggle the chemocline plane to compare the water surface with the oxygen boundary depth
- Read area, depth, and salinity figures in the panel
- Drag to orbit, scroll or pinch to zoom
- Runs fully in the browser with the vendored three.js engine - no account, no upload
| Figure | Published value |
|---|---|
| Surface area | about 436,400 sq km |
| Maximum depth | about 2,212 m |
| Mean depth | about 1,253 m |
| Oxic layer thickness | about 150-200 m before the chemocline |
| Anoxic volume share | about 90 percent of total volume - the largest anoxic basin on Earth |
| Salinity | about 18 parts per thousand, roughly half world ocean average |
| Bordering countries | Turkey, Bulgaria, Romania, Ukraine, Russia, Georgia |
| Outlet | Bosphorus Strait to the Sea of Marmara, then the Dardanelles to the Mediterranean |
For another basin defined by a dramatic depth contrast, open the Caspian Sea 3D Explorer, or compare the deepest point on Earth in the Mariana Trench 3D Explorer.
Everything renders on your device with WebGL. The 3D engine loads once (about 0.7 MB) and is cached.
This is an educational approximation - the basin profile, shelf boundary, and vertical scale are schematic teaching cues, not survey data.
Frequently Asked Questions
Why is the Black Sea called anoxic?
Below a thin oxygen-rich surface layer, only about 150-200 m thick, dissolved oxygen runs out almost completely - about 90 percent of the sea's total volume is anoxic (oxygen-free) down to the 2,212 m floor.
How deep is the Black Sea?
The maximum depth is about 2,212 m and the mean depth is about 1,253 m, though the northwest shelf near Ukraine and Crimea stays much shallower.
Why doesn't the deep water mix with the surface?
The Black Sea is strongly stratified: dense salty water flows in from the Mediterranean along the bottom while fresher river water sits on top, so the layers almost never mix - which is also why the deep anoxic zone stays oxygen-free.
Which countries border the Black Sea?
Turkey and Bulgaria and Romania to the south and west, Ukraine and Russia to the north and east, and Georgia to the east.
Is the Black Sea salty?
Yes, but only about half as salty as the open ocean - around 18 parts per thousand versus roughly 35 for world ocean average - because of heavy freshwater inflow from rivers like the Danube.
Is this a scientific terrain model?
No. It is an educational explorer using published figures - the basin profile, shelf boundary, and vertical scale are schematic teaching cues, not survey data.