Scientists have discovered a magnetic and thermal anomaly in a volcanic lake in New Zealand

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Scientists have discovered a magnetic anomaly and a hidden hydrothermal system at the bottom of Lake Rotorua, which is located in the center of a dormant underground volcano on New Zealand’s North Island.

Scientists came across unusual phenomena when updating and detailing the map of the bottom of this reservoir, writes Live Science with reference to GNS Science.

A New Zealand tourism website says clouds of steam drift around the lake’s shores, and the sulfur gives the water a “magical green-blue” color.

Scientists from the research institute discovered eruption craters at the bottom of Lake Rotorua, as well as an ancient river and a large magnetic anomaly in its southern part.

Photo: muha04/Depositphotos

The new map covers an area of ​​55 square kilometers, which is about 68% of the bottom of the lake.

Cornel de Ronde, chief scientist at GNS Science, said that seeing the new map is like putting on glasses for the first time and finally reading the fine print.

“Usually with volcanic rocks, when you run a magnetometer over the top of them, you get very positive anomalies, but in this case we get negative anomalies, probably because of very low magnetic susceptibility.”– said de Ronde.

He explained that volcanic rocks usually contain the highly magnetic mineral magnetite. But in Lake Rotorua, hydrothermal fluids seeped through the rock and turned the magnetite into pyrite (or fool’s gold) – a mineral without a magnetic signal, the scientists suggest.

This hydrothermal process could change the magnetic signal and explain the negative anomaly.

Map of magnetic anomalies of the lake

The researchers also found other evidence of hydrothermal activity in the same general area as the magnetic anomaly. The heat flow map shows that heat (which is probably hot water) is rising from the bottom. Hydrothermal eruption craters are also visible in this area.

Despite this activity, the water temperature at the bottom of the lake is usually around 14°C.

Scientists explain this by the large area of ​​the reservoir and the significant volume of water, which can counteract the heat coming from below. The water temperature usually fluctuates within 1°C during the month.

“No one swimming in the lake would notice it, but with the instruments we can see it“, the scientist added.

Read also: An ancient brick from Mesopotamia helped scientists discover a magnetic field anomaly

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