A cubic-kilometre cumulus holds roughly half a gram of liquid water per cubic metre, in tiny droplets. That adds up to about 500 tonnes of water floating overhead, the weight of a hundred elephants. It stays up because the droplets are so small they fall extremely slowly, and the rising air that builds the cloud keeps them aloft.
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.