About Sliding Shores

An interactive visualisation of Earth’s elevation, from the floor of the Mariana Trench to the summit of Everest.

Sliding Shores is a personal, non-commercial science visualisation. It renders Earth as a 3D globe and lets you drag a single slider to set the global sea level anywhere from −11,000 m (every ocean drained to the bottom of the Mariana Trench) to +8,849 m (water past the summit of Mount Everest). As you move the slider, coastlines retreat or vanish in real time, exposing dry continents on one extreme and submerging entire mountain ranges on the other.

The point isn’t to predict the future. The point is to give a physical, tactile sense of how thin the layer of habitable land really is, how much of the planet’s surface area is hidden underwater, and how dramatically that ratio has shifted across geological time. Most maps flatten the planet onto a rectangle and treat “sea level” as a fixed line. Sliding Shores treats it as a variable and shows you what happens when you move it.

The data

Sliding Shores uses ETOPO 2022, a global elevation map from NOAA. It includes both land height and ocean depth, so the globe can show what is above or below the sea level you choose with the slider.

Citation: NOAA National Centers for Environmental Information (2022). ETOPO 2022 15 Arc-Second Global Relief Model. NOAA NCEI. doi.org/10.25921/fd45-gt74.

The presets

The buttons above the slider are bookmarks to specific sea levels that either happened in Earth’s past, are projected for its future, or simply mark a vivid threshold. They are ordered from the deepest drained state on the left to the most extreme flooded state on the right.

Oceans drained (−11,000 m)

Empty every ocean basin all the way to the deepest known point on Earth, the Challenger Deep in the Mariana Trench. The continents become high plateaus rising several kilometres above an exposed seafloor of abyssal plains, mid-ocean ridges, hadal trenches, and seamount chains. This is geometry, not physics — the slider doesn’t care where the water went.

Ridges surface (−3,800 m)

At the average depth of the abyssal plain, the mid-ocean ridge system — the longest mountain range on the planet — pokes into daylight. You can trace its full S-curve down the Atlantic, through the Indian Ocean, and up into the Pacific.

Mediterranean drained (−1,500 m, ~5.5 Mya)

The Messinian salinity crisis. Tectonic movement closed the Strait of Gibraltar and the Mediterranean evaporated nearly to its floor over roughly 600,000 years, leaving behind kilometre-thick salt deposits that we still drill into today. When the Atlantic eventually broke back through, it refilled the basin in a flood that may have lasted only months — the Zanclean megaflood, possibly the largest single hydrological event in the planet’s history.

Dead Sea floor (−430 m)

The lowest exposed land surface on Earth today. Drop the global sea level to this point and the Dead Sea, the Caspian, and a handful of other endorheic basins are no longer outliers; they sit at world sea level.

Sunlight zone ends (−200 m)

The base of the photic zone — below this depth, sunlight is too weak for photosynthesis. It also happens to be roughly the edge of the continental shelf, so dropping the sea level here exposes the shelves as broad new lowlands.

Black Sea deluge (−155 m, ~7,600 years ago)

The Black Sea sat as a smaller, lower freshwater lake during the late Pleistocene. As global ice sheets melted and the Mediterranean rose, seawater eventually overtopped the Bosphorus sill and poured in. The catastrophic-flood version of this event — advanced by Ryan and Pitman — is debated, but the lake-to-sea transition is well established and may have displaced the Neolithic communities living on its old shorelines.

Ice Age (−120 m, ~20,000 years ago)

The Last Glacial Maximum. So much water was locked up in continental ice sheets that global sea level was about 120 m lower than today. Doggerland connected Britain to mainland Europe, Sundaland joined the islands of Indonesia into a single landmass, and humans walked from Siberia into Alaska across the exposed Bering land bridge.

Today (0 m, 2026)

The reference state. Roughly 29% of Earth’s surface is land; the rest is ocean averaging 3.7 km deep. Worth noting how small the slider movement needs to be in either direction before this ratio changes meaningfully.

2100 worst case (+1 m)

Aligned with the upper end of IPCC AR6 sea-level projections under high-emissions scenarios. The visible coastline change is subtle on a whole-planet view, but at this scale river deltas, atolls, and low-lying coastal cities — where most of the world’s people live — are where the impact is concentrated.

West Antarctic collapse (+3.3 m)

The West Antarctic Ice Sheet is grounded below sea level on a retreating bed, which makes it a candidate for marine ice-sheet instability — a self-sustaining collapse once a tipping point is crossed. Its full disintegration would commit the planet to about 3.3 m of additional sea-level rise over centuries.

Last Interglacial (+6 m, ~125,000 years ago)

The Eemian. Global temperatures sat about 1–2 °C warmer than pre-industrial, and sea level was around 6 m higher than today, sustained for thousands of years. Anatomically modern humans were already on the planet. It’s the closest natural analogue we have for a moderately warmer world.

Greenland melts (+7 m)

Roughly the sea-level equivalent of the Greenland ice sheet. Models disagree on the exact temperature threshold for irreversible melt, but the consensus floor sits not far above current warming.

All ice melts (+70 m)

Greenland plus East and West Antarctica plus every glacier. Florida is gone; large parts of Bangladesh, the Netherlands, and the eastern seaboard of the United States are gone; inland seas appear across the Amazon and West Africa. This is the asymptote of an ice-free-Earth scenario, not a near-term outcome.

Liberty’s head submerged (+93 m)

Vertical reference point. The Statue of Liberty’s torch sits roughly 93 m above mean sea level; at this slider position only the tip remains visible.

Cretaceous seas (+200 m, ~90 Mya)

The dinosaur-era highstand. Vigorous seafloor spreading inflated the ocean basins and pushed water onto the continents, drowning their interiors. The Western Interior Seaway split North America in two; much of Europe was an archipelago. There were no permanent ice caps anywhere on Earth.

Drown Everest (+8,849 m)

The far end of the slider. Only the summit pokes through. This is a thought experiment, not a hydrology one — there is not enough water on Earth to reach this level by any natural mechanism.

Caveats

Sliding Shores is a visualisation, not a forecast. Real sea-level change depends on ice mass, thermal expansion, isostatic rebound, ocean basin shape, and a long list of factors a single slider can’t represent. The deep-drained presets in particular are pure geometry — if you actually removed all that water, the crust would rebound, the basins would deform, and the resulting topography would not match what you see here. Treat the extreme positions as “what if” geometry, not climate science.

Coastlines on the globe also reflect modern continental positions; the deep-time presets (Cretaceous, Messinian, Eemian, Last Glacial Maximum) are shown using the present-day arrangement of continents for legibility. Plate tectonics has reshuffled the surface considerably over geological time, and a strictly correct palaeogeographic reconstruction would look different.

About the author

Sliding Shores is built and maintained by Richard Franklin as a hobby project. Questions, corrections, source-data suggestions, or bug reports are welcome at [email protected].