Which eruption was heard furthest away?

Krakatoa, on 27 August 1883, produced what is generally accepted as the loudest sound in recorded history. It was heard clearly on Rodrigues Island near Mauritius, about 4,800 kilometres away, where a police chief reported the distant roar of heavy guns. At 160 kilometres it was measured at about 172 decibels - loud enough to rupture eardrums well outside that.

The pressure wave circled the planet several times and was picked up by barometers around the world for days afterwards, which is how its power was quantified. Most of the 36,000 deaths were not caused by the explosion but by the tsunamis that followed, some over thirty metres high, which destroyed hundreds of coastal settlements.

It also changed the sky. Enough ash and sulphur reached the upper atmosphere to cool global temperatures by around a degree for several years and to produce vividly coloured sunsets worldwide - the strange red skies recorded in London and in paintings of the period. Krakatoa itself largely destroyed itself; a new cone, Anak Krakatau, child of Krakatoa, has been growing out of the caldera since 1927 and collapsed into the sea in 2018, causing another deadly tsunami.