In deserts, many rocks are coated with a thin, dark, shiny film: desert varnish. Rich in manganese and iron oxides, it builds up extremely slowly, on the order of a few micrometres per thousand years. Its exact origin, dust or microbes, is still debated. Ancient peoples carved their petroglyphs by scratching through this varnish to reveal the paler rock underneath.
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.