About Contourlines
Contourlines is a free, open-source interactive contour map of Earth and sea level rise simulator. It renders real NOAA elevation and ocean depth data as a classic topographic map — isolines, hypsometric tints, hillshading — that scrolls seamlessly around the planet and morphs into a 3D globe when you zoom out.
How to use it
- Drag to pan — the map wraps endlessly, east to west.
- Scroll or pinch to zoom. Fully zoomed out, the map becomes a globe.
- Drag the sea level slider to raise or lower the ocean — the scale is exponential, spanning the full planet from the Mariana Trench (−11,000 m, oceans fully drained) to Mount Everest (+8,848 m, everything submerged). Coastlines, contour lines, and hypsometric colors all re-map to the new waterline instantly, while a crimson reference line keeps marking where today's coastline used to be.
- Try the presets: −120 m shows Ice Age coastlines with land bridges like Beringia and Doggerland; +70 m shows the world if all ice melted.
Frequently asked questions
- What would happen if all of Earth's ice melted?
- Sea level would rise about 70 meters. Set the slider to +70 m and watch low-lying regions — the Netherlands, Bangladesh, the Nile delta, Shanghai, southern Florida — disappear beneath the new coastline.
- What was sea level during the last Ice Age?
- About 120 meters lower than today. At −120 m you can walk from Siberia to Alaska across Beringia, and Britain joins Europe across Doggerland.
- How accurate is this?
- Elevations come from NOAA's ETOPO1 Global Relief Model at 5-arc-minute resolution (~9 km per cell). The simulation is a static "bathtub" model for education — it ignores tides, storm surge, isostatic rebound, and coastal defenses.
- Does it track me or need a server?
- No. Everything runs locally in your browser with WebGL2. No cookies, no analytics, no accounts.
Data & credits
Elevation & bathymetry: NOAA ETOPO1 Global Relief Model (public domain), NOAA National Centers for Environmental Information. Source code: MIT-licensed on GitHub.