How China’s Three Gorges Dam Literally Shifted the Earth

When people say humanity has changed the face of the planet, it’s usually a metaphor. But in the case of China’s Three Gorges Dam, it’s almost literal.

According to NASA, this colossal feat of engineering, which holds back around 10 trillion gallons of water (about 39 trillion liters), has shifted the Earth’s axis of rotation by nearly two centimeters. The reason is as elegant as it is profound: redistributing so much mass on the planet’s surface changed the moment of inertia of the Earth — and therefore, the speed at which it spins.

The effect isn’t catastrophic, of course — a day on Earth became shorter by about 0.06 microseconds. But the fact itself is astonishing: by building a dam, humanity has managed to make a measurable change in the planet’s geophysics. Not through a meteor strike or volcanic eruption — simply through ambition and concrete.

The Three Gorges Dam stretches 2.3 kilometers across, rises 181 meters high, and its reservoir snakes nearly 600 kilometers upstream along the Yangtze River. Seventeen years in construction and completed in 2012, it now provides electricity to tens of millions of homes, controls floods — and quietly reminds us that humans can alter not just the climate, but the mechanics of the planet itself.

The Earth with Gravitational Bumps

When such vast reservoirs are filled, the planet’s surface develops something akin to a “gravitational bump” — an area where gravity becomes slightly stronger due to the concentration of mass.

Satellites like NASA’s GRACE and GRACE-FO missions can literally feel these bumps: their orbits dip ever so slightly, as if the spacecraft were gliding over an invisible gravitational hill.

After the filling of Egypt’s Lake Nasser or China’s Three Gorges reservoir, new “bulges” appeared in global gravity maps — tangible traces of human engineering visible from space.

Five Other Man-Made Giants That Shook the Planet

1. The Aswan High Dam (Egypt)
Built in the 1960s and 70s across the Nile, it altered the local gravitational field and caused measurable ground subsidence. Satellites recorded a new gravitational bump forming over the Nile Valley.

2. Tokyo (Japan)
One of the heaviest megacities on Earth literally presses down on the crust. Urban infrastructure and dense development exert tens of billions of tons of pressure, causing slow but measurable subsidence.

3. The Hoover Dam (USA)
After Lake Mead was filled in the 1930s, tectonic stresses shifted and small earthquakes began to occur — the phenomenon that scientists later named induced seismicity.

4. North American Water Redistribution Projects
Thousands of dams, canals, and irrigation systems built in the 20th century changed the distribution of water across the continent so dramatically that GRACE satellites detected it as a shift in the planet’s overall mass balance.

5. Human-Driven Glacier Melt
Not a single structure, but the largest man-made impact on Earth’s mass balance. As trillions of tons of ice melt from Greenland and Antarctica into the oceans, the planet’s axis of rotation shifts and its rotation slightly accelerates — an effect even greater than that of the Three Gorges Dam.