The Continent Beneath the Ice
Antarctica's real surface is two kilometres down. Six decades of radar flights have finally drawn it: a highland continent on one side, a drowned basin on the other, and the deepest ground on Earth — ground no one will ever stand on.
That is the deepest point of any landmass on the planet — about eight times lower than the Dead Sea shore, the lowest land you can actually walk to. It is filled, to the brim and beyond, with ice.
Almost half of Antarctica is a basin
Take the ice away and 46.7% of the grounded bed — 5.65 million square kilometres, an area the size of the European Union plus India — lies below sea level. West Antarctica is barely a continent at all: it is an archipelago holding its breath.
Bed elevation, one hue light to dark. Every tick is a measured value; the Dead Sea is there only to show how far outside the ordinary range Antarctica’s bed sits.
The deepest hole on land, by a factor of eight
Every other contender for "lowest land" is a lake shore. Antarctica's contenders are canyons that have never been open to the sky.
Denman from BedMachine Antarctica (mass-conservation reconstruction, 500 m grid). Byrd is the deepest cell in the Bedmap3 grid — two methods, two answers, and the gap between them is the honest measure of how well we know this place.
Two kilometres of ice, on average
Mean grounded ice thickness is 2,148 m. The thickest column ever measured — 4,757 m — sits in an unnamed canyon in Wilkes Land, at 76.052°S, 118.378°E. That is Mont Blanc, buried, with room to spare.
1,948 m if you include the floating ice shelves.
Enough, if it all melted, to raise global sea level by 58 m.
21,745 km² of exposed ground — everything else is under ice.
Cross-section is schematic; the labelled values are measured. Bedmap3 (2025); ice-free area from Burton-Johnson et al. (2016).
How you map a landscape nobody has seen
You fly over it and listen. Radar pulses pass through ice, bounce off rock, and come back; each flight line draws one thread of the map. Bedmap3 added 84 new airborne surveys, 52 million new data points and 1.9 million line-kilometres to everything gathered since the 1950s.
Across 84 new aero-geophysical surveys from 15 data providers.
Averaged over the continent. In the deep interior the nearest sounding can be much further away — which is why two datasets can disagree about where the deepest point is.
*Bedmap1's total is derived, not published: Bedmap2 reported "over two orders of magnitude more" points than Bedmap1, so ≈0.25M is an illustrative upper bound, not a measured figure.
There is liquid water down there
Pressure and the Earth's own heat keep the base of the ice sheet at melting point in places. 675 subglacial lakes are now known in Antarctica — one dot each, below.
About 12,500 km² of liquid fresh water, sealed under roughly 4 km of ice near the centre of East Antarctica. It is the largest of the 675 — the orange dot.
Lakes fill, drain and refill, lubricating the ice above them. They are one reason the bed map matters as much as the surface map: water moves along the shape of the bed, not the shape of the ice.
Why a bed below sea level matters
Ice grounded on rock above sea level can only melt from the top. Ice grounded below sea level can be undercut from beneath by warm ocean water — and where the bed slopes downward inland, the retreat can feed itself. Read that way, the bed map is a risk map.
The total locked up in 27.17 million km³ of ice.
±0.3 km, from satellite radar interferometry — and it is retreating into the deepest trough on land.
46.7% of the area under the grounded ice sheet.
- 01The colour split is the real border. East Antarctica (ochre) is old, high, continental rock. West Antarctica (dark blue) is mostly below sea level — a different kind of place under the same white sheet.
- 02The deepest points hug the coast. Denman, Byrd and Thwaites all sit where ice drains fastest: narrow, deep troughs are what let that much ice reach the sea.
- 03The empty middle is not empty. The Gamburtsev range under the pole-side interior has Alpine relief of 2–3 km and has never been seen — only heard, by radar.