As snow piles up, it traps tiny air bubbles that end up sealed in the ice. By drilling more than 3 km down, scientists recover cores whose bubbles are genuine samples of past atmospheres. The EPICA core at Dome C spans roughly 800,000 years of continuous history, and newer drilling projects aim to reach back more than a million years.
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.