Whakamaru Caldera


Whakamaru Caldera was created in a massive supereruption 335,000 years ago and is approximately in size and is located in the North Island of New Zealand. It now contains active geothermal areas as well as the later Maroa Caldera.

Geography

The Whakamaru Caldera covers an area larger than the younger Taupō Volcano to its south and indeed the rims overlap. To its north the more recent eruptive centres have sometimes been grouped as the Mokai Ring Complex or Maroa Volcanic Centre. It contains to its north east the more recently active Maroa Caldera with the Ben Lomond Dome being outside the southern border of the Maroa Caldera but definitely a feature of the Whakamaru Caldera.
Domes within the caldera include the Western Dome Complex, including Pokuru which defines its north western borders, Forest Road Dome, Puketarata, Ngangiho, which is high but beaten by Ben Lomond, and Marotiri just to the west of Kinloch.

Geology

The first eruptions may have occurred half a million years ago, but the period 320,000 to 340,000 years before the present have been characterised as:
  1. Whakamaru eruption
  2. *Massive eruption sequence over less than a thousand years with a VEI of 8 producing of tephra about 335,000 years ago. This age in the most recent literature has slightly moved back to 340 ± 5 ka. This is the largest known in the Taupō Volcanic Zone and had at least three rhyolytic and one basaltic eruption in its sequence.
  3. *Although accumulation of the magma mush may have been over more than 200,000 years there is increasing evidence that eruption only became possible over a period that may have been as short as 10 years through a rapid thermal pulse or pressure change.
  4. *From sea core sediment studies it is known that it deposited the widespread Mount Curl/Rangitawa Tephra, dominantly to the southeast, extending across the landmass of New Zealand, and the South Pacific Ocean and Tasman Sea. The eruption has been calculated to have been dense-rock equivalent and modelled to have produced a Plinian column approximately high. At the Chatham Islands which is more than from the Whakamaru Caldera the deposits are up to thick. About from the source in New Zealand itself the Rangitawa Tephra is up to thick so a large area of the planet's biosphere would have been impacted.
  5. *Whakamaru ignimbrite
  6. **Found over an area of mainly to west of caldera
  7. **Up to thick
  8. *Rangataiki ignimbrite
  9. **Found mainly to east of caldera
  10. Mananui eruption. Also shown is the modern Taupō Rift, Hauraki Rift and landmarks of Lake Taupō and Lake Rotorua.