Along the East African Rift, the African plate is slowly splitting. In 2005, in Ethiopia's Afar region, a fissure some 60 km long opened in a matter of weeks, pulling the ground apart by several metres. Millions of years from now, the sea could flood the rift and cut off part of East Africa, just as the Red Sea once separated Arabia from Africa.
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.