Oruanui eruption

The Oruanui eruption (also known as the Kawakawa eruption or Kawakawa/Oruanui event) of Taupō Volcano in New Zealand around 25,700 years before present was the world's most recent supereruption, and its largest phreatomagmatic eruption characterised to date.

Geography

At the time of the eruption, the sea level was much lower than at present, and for over 100,000 years the Taupō Volcano had been mainly under Lake Huka, a larger lake than the present Lake Taupō. Lake Huka was destroyed in the eruption, and other features of the local geography were changed significantly as outlined below.

Eruption

With a Volcanic Explosivity Index of 8, it is one of the largest eruptions ever to occur in New Zealand and the most recent supereruption. It occurred 25,675±90 years BP in the Late Pleistocene. It generated approximately 430 km3 (100 cu mi) of pyroclastic fall deposits, 320 km3 (77 cu mi) of pyroclastic density current (PDC) deposits (mostly ignimbrite), and 420 km3 (100 cu mi) of primary intracaldera material, equivalent to 530 km3 (130 cu mi) of rhyolitic magma, totalling 1,170 km3 (280 cu mi) of total deposits. As such it is the largest phreatomagmatic eruption characterised to date. The eruption is divided into 10 different phases on the basis of nine mappable fall units and a tenth, poorly preserved but volumetrically dominant fall unit.

Modern-day Lake Taupō, 616 km2 (238 sq mi) in area and 186 m (610 ft) deep, partly fills the caldera generated during this eruption. A 140 km2 (54 sq mi) structural collapse is concealed beneath Lake Taupō, while the lake outline at least partly reflects volcano-tectonic collapse.