As the southern winter sets in, the Southern Ocean freezes around the continent. Sea ice grows from about 3 million km² in February to around 18 million in September, more than the area of Antarctica itself, roughly 14 million km². It is one of the largest seasonal changes visible on the face of the planet.
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.