New Zealand’s supervolcano Lake Taupō is still highly active  

We all know about volcanoes. But have any of you ever come across the term supervolcanoes? Well, Google defines it as a volcano whose eruption has a Volcanic Explosivity Index (relative measure of the explosiveness of volcanic eruptions) of 8, that is considered to be the largest recorded value on this index. It was formulated by the duo, Chris Newhall of United States Geological Survey and Stephen Self of the University of Hawaii in 1982. Recently, one of world’s most prominent and hazardous supervolcanoes, named Lake Taupō has been in the news. Let us tell you why. Scientists have recently found out that the volcano, that was so long considered to be dormant, is in fact, still highly active. That is why the lake bed has been falling and rising persistently. The recent findings have been published in the New Zealand Journal of Geology and Geophysics. Here, take a closer look at Lake Taupō with us! 

Lake Taupō: A bird’s eye view 
Taupō is a caldera volcano located on New Zealand’s largest freshwater lake. If you are wondering what a caldera is, it is a large crater or cauldron-like hollow formed when the edifice of a volcano collapses. The volcanic materials of Taupo are rich in silica. Scientific research suggests that Lake Taupō has been active at least 25 times in the past 12000 years. In fact, this supervolcano has been responsible for producing earth’s two most volatile eruptions: Oruanui that took place 25,600 years ago and the more recent Hatepe eruption, that happened around 232 AD. Both these eruptions have not only shaped the modern caldera but also released intense amounts of pumice, ash and other volcanic materials into the atmosphere.  

How did scientists find out about Lake Taupō’s active state? 
In order to find the answer to this question, we have to go back to 1979 when the science fraternity had decided to initiate an experimental project on Lake Taupō. Their objective was to monitor the lake levels in order to detect upcoming volcanic and tectonic shifts, if any.  

Okay, so how did they go about it? Turns out, the team of researchers involved in this project installed fixed survey stations around the lake site. The one deserving special mention was the design of the purpose-built platform on Horomatangi Reef, which was the primary vent of the 232 AD eruption. What they did next was really impressive. They hung customised water gauges from various fixed points (22 in number) and used the platform as the base to trace the lake level alterations. The technique was so effective that it even enabled the detection of minute station height changes.  

Okay, but you must be wondering why the scientists chose this particular method. Well, because they were almost certain that in order to determine whether the supervolcano was at all active or not, this was the only way to detect the movement of magma, however negligible it may be. Moreover, the team of researchers involved in the project had hoped that this particular system would also provide them an explanation of the prolonged earthquake swarm that happened in the region in 1922. Looks like, they were right. The method did help them detect the plausible causes behind the earthquakes.  

Lake Taupō: What we know so far  
Until 1983, the project did not generate any result. However, soon, the Kinloch Station, located 10 km west of the Lake Taupō, was detected to be alternatively subsiding and rising. In fact, locals around the area also reported several instances of earthquakes around the same time.  

Initially, the geologists thought that the earthquakes were a result of tectonic shifts, but soon after a series of analysis, they realised that they were also caused by volcanic activity nearby. Since then, more such data has come to the forefront revealing movements of magma and tectonic faults that force the ground above the supervolcano to slide, up and down. In fact, over the years, it has been observed that during any form of tectonic activity, the north-eastern side of the lake, that is closest to the centre of the volcano rose; the lake bed sank; while the southern side was mostly undisturbed with only occasional subsidence.  

According latest reports, the volcano has caused an upliftment of 160mm near the Horomatangi Reef, while towards the north of the lake, they have caused a subsidence of 140mm. As you can guess, these mean that Lake Taupō is still very much active as well as dynamic in nature, closely related to surrounding tectonics. Interestingly, in the recent years, the project has also taken the help of satellite and seismic monitoring to further their research.