water-cycle

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.

The same water that fell as rain on a dinosaur is in your glass today. Here's how Earth's water cycle works, why it matters, and how climate change is rewriting it.