Water's boiling point depends on air pressure. At the summit of Everest, the pressure is only about a third of that at sea level, so water boils at around 70 °C. That is not hot enough to cook pasta or an egg properly, which is why climbers and high-altitude cooks often rely on pressure cookers.
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.