In its lower reaches, the Congo River drops in places to more than 220 m deep, according to measurements made in 2008 by the US Geological Survey. These chasms, carved by ferocious currents, cut off fish from one bank to the other. As a result, closely related species have evolved separately on either side of the river.
On 27 August 1883, the eruption of the Indonesian volcano Krakatoa was heard as far away as Rodrigues Island, nearly 4,800 km away. Its pressure wave was picked up by barometers worldwide and circled the globe several times. The tsunamis that followed killed more than 36,000 people.
The deepest known point in the ocean, Challenger Deep, lies roughly 10,900 m below the Pacific surface. Drop Everest in and its summit would still sit about 2 km underwater. Down there, the pressure is more than 1,000 times what you feel at sea level, roughly a tonne pressing on every square centimetre.