I recently read an excellent history of the Krakatoa explosion, Simon Winchester’s Krakatoa: The Day the World Exploded. The book touches on everything from Dutch colonialism to how the discovery of gutta-percha revolutionised communications technology. It also, naturally, discusses similar supervolcanoes, such as Tambora – also in Indonesia – which exploded less than half a century before Krakatoa.
Tambora was an order of magnitude bigger than Krakatoa (Volcanic Explosive Indices of 7 and 6, respectively). The recent Tonga-Hunga explosion was, by comparison, a ‘mere’ VEI of 5.
Bigger than both of those, with a VEI of 8, was New Zealand’s own Taupo.
That was 26,000 years ago. Taupo’s most recent major eruption was around 180-233 AD. Long before human arrival in New Zealand. Although the Taupo volcanic zone has experienced eruptions into historic times, Taupo itself has been quiet for nearly 2000 years.
But that doesn’t mean it will stay that way forever.
Deep in the ground below [the lake], geological unrest is brewing, according to a new paper in the New Zealand Journal of Geology and Geophysics.
Researchers have spent the last half-century using gauges at 22 sites around and across the lake to monitor its seismic activity. Real science, then, not Matauranga Maori. I guess praying to taniwha is not exactly the ‘equal’ of ‘Western’ science, like seismometers.
Their data suggest that the old supervolcano is still grumbling to itself, deep below the ground.
In early 1983, the system detected rising or falling across different sites. Not long after, a swarm of earthquakes gently shook the region, resulting in the rupturing of several faults that pushed the central Kaiapo fault belt down and caused other areas at the lake’s south end to rise […]
The authors noticed that during periods of geological unrest, the north-eastern end of the lake (which is closest to the volcano’s center and the adjoining fault lines) tended to rise; the lake bed near the fault belt’s center sank; and at the lake’s southern end, there was some minor subsidence.
“Within the lake, near Horomatangi Reefs, the volcano has caused 160 mm [16 cm or 6.3 inches] of uplift, whereas north of the lake the tectonic faults have caused 140 mm [5.5 inches] of subsidence,” [Finn Illsley-Kemp] said.
Science Alert
Yet, this region has very few earthquakes than surrounding areas. Which may point to it as the site for Taupo’s magma reservoir: because the deep rock is too hot and molten for earthquakes to occur.
The good news is that 16cm of uplift isn’t exactly anything to panic about – unless it buggers your house or cracks the pipes.
Taupo will eventually erupt again… some time in the next few thousand years. Plenty of time to get your insurance in order.
Meanwhile, researching the volcano’s behaviour (with ‘Western’ science) will build up a picture of its normal (ie non-explodey) behaviour – and what to watch out for, if things are going to possibly get a whole lot more explodey.