Volcanic Activity in Lake Rotoiti

Understanding the Affects of Under Water Volcanic Activity on Lake Rotoiti

Volcanologist and PhD researcher from Victoria University of Wellington, AJ Marshall, has been working on our lake to understand it! AJ has been collaborating with Te Arawa Lakes Trust (TALT) and Te Pu Ao (GNS) to collect data on the underwater volcanic activity at Rotoiti, to understand its potential impacts on the local environment and community.

The team is utilizing cutting-edge robotic technology to measure temperature and volcanic carbon dioxide (CO2) dissolved in the water, and the gas emissions from the surface over the last year. 

Measuring water properties, CO2, and chemistry of volcanic bubbles can provide information about the ongoing volcanic and magmatic processes and interaction of gases with lake water. The team are working to capture video footage of the deep volcanic basin within the lake and create a device to collect bubbles directly from the volcanic vent, alongside a range of chemical data.

So far, results show that summer heating of the lake surface of Rotoiti traps volcanic CO2 in the colder water deep within the lake, which accumulates until Autumn, when the top 20 metres of the lake cools and allows the water to mix and expel CO2 through the surface. Over the next year, these scientists will work to determine how much CO2 is being trapped deep in the lake, how this impacts native species, and how it disperses into the atmosphere.

This CO2 build up acidifies the water and replaces oxygen, making it uninhabitable for fish and kōura, which are forced to move to the warmer shallows. These acidic volcanic environments can encourage algae and extremophile growth. It appears that this is a natural process that has been occurring annually for centuries, but the full extent of the cyclical process is yet to be fully understood.

High levels of CO2 build up have been related to hazardous ‘limnic overturn eruptions’, where CO2 releases instantaneously, but the seasonal cooling of the lake surface makes this risk appear minimal. However, with summers increasing in intensity or length, due to climate change, the possibility may increase, as the potential to trap CO2 is increased. This collaboration hopes to quantify and understand if there is a hazard to local communities and monitor and mitigate any risk.

At the culmination of this PhD thesis, AJ plans to return to present results from their research. Until then, feel free to contact them at aj.marshall@vuw.ac.nz, and see the following links to:

(1) monitor the stratification and acidification of Rotoiti and

(2) see a detailed bathymetry of the lake which shows the deep volcanic features.