On the shores of Lake Rotorua, New Zealand, lies a mystery. This body of water hides beneath its calm surface the signs of a tumultuous past. Some 220,000 years ago, a volcanic eruption of epic proportions created this lake, above the now dormant volcano that lies silent in its bed.
The quiet of the lake hides a secret: i hydrothermal systems, direct heirs of volcanic activity of the past, continue to influence the lake ecosystem in ways that have so far only been understood. Recently, a team of researchers from New Zealand’s GNS Science Institute undertook an unprecedented exploratory mission, extensively mapping the bottom of Lake Rotorua.
Their work revealed the presence of countless small craters, evidence of underlying hydrothermal activity, and a curious magnetic anomaly (it wouldn’t be the first we discovered). The latter, in particular, has caught the attention of scientists: volcanic rocks, usually rich in magnetite and therefore highly magnetic, here show negative signals, probably due to the transformation of magnetite into pyrite, a mineral almost devoid of magnetic signal , due to the effect of hot water.
Such discoveries they not only confirm that the geothermal systems under the lake are still active, but they also open the door to new questions about the complex interaction between water, rock and heat in this area. The magnetic anomaly, together with the measured heat fluxes and craters, suggests the existence of a still unexplored hydrothermal system, perhaps linked to an ancient river discovered near the shore.
By the way, did you know that a new volcano was born in Iceland?