深海 · ABYSS · Ocean zones
Abyss
Abyssopelagic · 4,000 – 6,000 m
More than half of Earth's surface is a plain at this depth. Two degrees, total darkness, and almost nothing happening for tens of millions of years. This is the ocean's normal condition.
Descend this zone at true scaleDepth 4,000 → 6,000 m
The male dissolves into the female
Male black seadevils are a fraction of the female's size. Once he finds her, he bites on and fuses — skin, blood vessels and all — becoming a permanent, parasitic mate fed by her body for life.
Recorded as deep as 4,500 m
The flattest place on Earth
An abyssal plain can run a thousand kilometres and vary by only a few metres. Sediment settling for millions of years has buried the topography completely.
Roughly 50% of the planet's surface
Gold, dissolved
Seawater is estimated to hold around 20 million tonnes of dissolved gold — far too diluted for any method to recover it.
Most volcanoes are underwater
Three quarters of the magma erupted on Earth comes out on the seafloor. The mid-ocean ridge runs 65,000 kilometres, the longest mountain range on the planet — and almost none of it has ever been seen.
Over a million seamounts estimated · the vast majority unvisited
A single cell the size of your palm
A xenophyophore is one cell. It grows to 20 centimetres across, holds thousands of nuclei inside that single cell, and is among the most abundant large organisms on the abyssal floor.
One of the largest single cells known
What the ocean swallows
The ocean absorbs about a quarter of the carbon dioxide humans emit — and pays for it with acidification.
Bigfin squid
Its arms can be many times longer than its body and trail down bent at sharp angles, like elbows. It has only ever been filmed alive a handful of times, by deep submersibles.
Bismarck
Her steering gear destroyed, the battleship was circling when she went down. When she was found in 1989 the hull was almost intact — too deep and too cold for corrosion to do much.
Whether she was scuttled or sunk is still argued
2,086 dead · 114 survived
Stardust in the abyssal clay
Tens of thousands of tonnes of cosmic dust fall to Earth each year. On land it is stirred away within seasons, but on abyssal plains, where sediment accumulates almost imperceptibly, the grains remain as a layer. Deep-sea clay is an archive of the solar system.
Micrometeorites · concentrated in red clay that builds a few millimetres per thousand years
The actual majority
The sea pig is a sea cucumber that walks across mud on leg-like tube feet. On some abyssal plains sea cucumbers make up 95% of the large-animal biomass. The ocean does not belong to whales.
Genus Scotoplanes · they travel in herds facing the same way
Noise that drowns out a whale's call
Cargo ship engines send noise hundreds of kilometres through the water, drowning out the calls whales use to find each other.
Metal the size of a potato
Manganese nodules contain nickel, cobalt and rare earths, and grow a few millimetres per million years. A test-mining track cut in 1979 had not recovered forty years later.
Clarion-Clipperton Zone · 88 – 92% of the species found there are still unnamed
Gummy squirrel
A sea cucumber that raises a tail-like sail and glides across the mud. The nickname is purely about looks — it has nothing to do with an actual squirrel.
Among the oldest living things
Some glass sponges are estimated to be several thousand years old — among the slowest-living, longest-lived animals on Earth.
A sea within the sea
Hyper-salty water seeping from the seabed pools into brine lakes that sit at the bottom like a separate sea. Most animals avoid even the edge.
Death becomes infrastructure
When a whale sinks, an ecosystem forms where it lands. Hagfish and sharks strip the flesh, worms take the remaining tissue, and finally bacteria break down the fat inside the bones. The sequence runs for over fifty years, and more than a hundred species are known only from whale bone.
Scavenger stage 2 years → opportunist 2 years → sulphophilic 50 years +
A Cold War ear that overheard whales
SOSUS, a Cold War hydrophone network built to track submarines, was declassified and is now used to study whale calls and undersea earthquakes.
A shrimp relative the size of a housecat's tail
Most amphipods are smaller than a fingernail. Alicella gigantea grows to 34 cm and earns the nickname 'supergiant,' swarming over carcasses that drift down to the seafloor.
Recorded from 5,000 to 8,931 m
The limit of its era
- 4,050 m FNRS-3 — the limit of human reach
What fits in this depth
| Depth | |
|---|---|
| 4,478 m | Matterhorn |
| 4,809 m | Mont Blanc |
| 5,895 m | Kilimanjaro |
Figures come from public observational data; sources are cited in the main descent. Do not use for navigation, diving, or any safety decision.