The narrow routes that move our world
How a handful of sea passages connects factories, energy supplies, and everyday life.
Read the story
FIELD NOTES / 01GEOGRAPHY · THE HIDDEN EARTH
AN INTERACTIVE EXPEDITIONBeyond
Beyond
the surface.
From the ground beneath your feet to the iron heart of a planet. Take a journey through the world we never see.
6,371kmFROM SURFACE TO CENTRE · MEAN RADIUS
CrustMantleOuter coreInner core
YOUR DEPTH
SurfaceCentre · 6,371 km
SOLID ROCK
A very thin place to call home.
The crust is the outer rock layer. Its thickness varies: oceanic crust is much thinner than continental crust. This journey uses a simplified 35 km continental crust.
A tectonic plate includes the crust and the rigid uppermost mantle.
A simplified continental route: crust to 35 km, mantle to about 2,900 km, outer core to about 5,150 km, then inner core. Real boundaries vary. The marker follows radial depth; this is a visual model, not a physical travel simulation.
A CHANGE OF PERSPECTIVEWe have barely
We have barely
scratched the surface.
≈0.2%
The Kola borehole extends just over 12 km down—about two-tenths of one per cent of the distance to Earth’s centre.
Drilling depth6,371 km to the centre
Proportional bar. The tiny mark is the point.FIELD NOTES / 02 · A QUESTION OF SCALEEven Everest
Even Everest
would disappear.
Imagine an Everest-height mountain on the floor of the deepest ocean. Would its summit reach the surface?
EVEREST’S ELEVATION8,849 m
Above sea level. Now lower that height to the floor at Challenger Deep.
EVEREST8.849 kmabove sea level
CHALLENGER DEEP10.935 kmbelow sea level
Vertical scale is proportional. This compares Everest’s elevation with ocean depth; it does not represent the mountain’s real base or shape. Depths are approximate.
FIELD NOTES / 03 · THE SHAPE OF THE WORLDThe world isn’t
The world isn’t
the size you think.
On a Mercator map, Greenland looks as big as Africa — even slightly bigger. Slide to an equal-area map.
ON THIS MAP, GREENLAND ISof Africa’s drawn area
IN REALITY7%Africa is about 14× larger
Mercator · preserves local angles, inflates area away from the equator.
GREENLAND2.17M km²
AFRICA30.37M km²
RATIO≈ 14×
Natural Earth 1:110m outlines, simplified. Antarctica omitted: Mercator cannot show the poles. Equal-area maps keep sizes true but distort shapes — no flat world map is free of distortion. Areas: CIA World Factbook (Greenland), Britannica (Africa).
HOW CAN WE KNOW?
Listening to a planet.
Earthquake waves change speed and direction as they pass through different materials. Shear waves do not travel through the liquid outer core. Together with gravity, magnetic measurements, and laboratory experiments, these signals reveal an interior we cannot visit.
Read the story of Earth’s interior →FOLLOW THE CONNECTIONS
Explore another subject →From Earth to everything else.
Sources, measurements & model notes
Original educational illustrations. Layer boundaries are rounded; the crust is enlarged in the cutaway. Ocean depths vary with location and measurement. Map outlines are simplified Natural Earth data (public domain); Antarctica is omitted from the projection comparison. Reference sources checked 13 November 2026.
NASA · Earth’s mean radius ↗NASA · Earth’s structure ↗USGS · Inside the Earth ↗USGS · Seismic evidence for the interior ↗USGS · Crustal thickness ↗NASA · The Kola borehole ↗NOAA · Everest and Challenger Deep ↗NOAA · How deep is the ocean? ↗Ordnance Survey · Map projections (More than Maps) ↗USGS · Map projections: a working manual (Snyder, 1987) ↗Šavrič, Patterson & Jenny · The Equal Earth map projection (2018) ↗CIA World Factbook (2023) · Greenland, area — independent archive ↗Encyclopaedia Britannica · Africa, area ↗Natural Earth · 1:110m Admin 0 countries (public domain) ↗
Sources inform the explanations; these organisations do not endorse this website.