The picture of endless dune seas is misleading. According to the US Geological Survey, sand covers only about 20% of the world's deserts. The rest is mostly rocky plateaus, gravel plains, dried-up lake beds and bare mountains. Even in the Sahara, the great dune seas make up only a minority of the landscape.
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.