After water, sand is one of the most exploited resources on Earth: tens of billions of tonnes of sand and gravel are extracted every year, according to the UN Environment Programme. The paradox: desert sand is largely unusable for concrete. Polished by the wind, its grains are too round and smooth to bind well. So builders mostly draw on rivers and coastlines.
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.