A desert is defined not by heat but by dryness: roughly less than 250 mm of precipitation a year. By that measure, the largest desert on the planet is Antarctica, at about 14 million km², far ahead of the Sahara's 9 million or so. In the heart of the plateau, only a few centimetres of snow, in water equivalent, fall each year.
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.