Unlike the South Pole, which sits on a continent, the North Pole lies in the middle of the Arctic Ocean. Beneath your feet there would be just a few metres of drifting sea ice, then more than 4,000 m of water down to the seabed. No marker can stay there for long: anything planted in the ice drifts away with it.
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.