The seafloor is the bottom surface of the ocean, the vast underwater landscape that covers more than 70% of Earth's surface. Just as land has mountains, valleys, and plains, the seafloor has its own dramatic terrain: towering underwater mountain ranges called mid-ocean ridges, deep trenches that plunge miles below the surface, and wide, flat areas called abyssal plains.

For most of human history, the seafloor was a complete mystery. People could sail across oceans but had no idea what lay beneath. Only in the last century have submarines, sonar, and deep-sea robots allowed scientists to map and explore these hidden depths. What they discovered amazed them: the seafloor is geologically active, constantly changing as Earth's tectonic plates shift and spread apart. New seafloor forms at mid-ocean ridges where hot magma pushes up from below, while old seafloor gets pulled back into Earth's interior at deep trenches.

The seafloor hosts remarkable life too. Near volcanic vents on the ocean floor, strange creatures survive in complete darkness, thriving on chemicals instead of sunlight. Even at crushing depths where the pressure would flatten most things, life finds a way to flourish in the cold and dark.