oceans

Ocean water is salty primarily because rain and rivers slowly weather rocks on land, dissolving ions like sodium and chloride and carrying them to the sea. When seawater evaporates, water leaves but salts remain and accumulate over geological time. Hydrothermal vents and volcanic activity add dissolved minerals. The ocean sits near steady state, with salt being removed about as fast as it arrives.

What causes ocean tides? The Moon's differential gravity, why there are two high tides daily, spring and neap tides, and tidal locking — explained.

What would happen if every drop of water on Earth vanished? Explore the catastrophic consequences for life, atmosphere, and planet.

The Pacific Ocean covers nearly a third of Earth's surface and holds about half the planet's water. This thought experiment walks through what physics, climate science, and geology say would happen if it vanished — and why the planet has no substitute for it.

An Earth covered entirely by ocean — a 'water world' — would have no terrestrial life, simpler climate dynamics, and a chemistry profoundly altered by the absence of continental weathering. Land has shaped Earth far more than most people realize.

Coastline length is one of geography's most measurement-dependent numbers. This ranking shows which countries have the longest coastlines, why Canada leads by a wide margin, and why different datasets disagree.

Earth spins at 1,674 km/h at the equator. If it suddenly stopped, supersonic winds would devastate the surface. If it slowed gradually, the consequences are still severe — a 6-month day, ocean redistribution, and a collapsing magnetic field.