By Losirene Lacanivalu, Cook Islands News
From left, Ngatupuna Kae of the National Environment Service, Dr. John Parianos - Knowledge Management Director (SBMA), Edward Herman - Partnerships & Cooperations Director (SBMA) and Keanu Harawira (NES Ranger). Photo: Cook Islands News / Moana Minerals
Researchers have discovered a potentially younger and active volcanic hotspot beneath the Cook Islands' waters, prompting excitement for geological understanding and raising calls for caution regarding seabed mining.
The Seabed Minerals Authority (SBMA) is calling it "an exciting new discovery" by its scientists in partnership with National Institute of Water and Atmospheric Research (NIWA), the University of California Santa Barbara and Kiva Marine.
According to SBMA, these volcanoes are several kilometres underwater and "not explosive" like those in Tonga or Indonesia.
However, they could be key to understanding the region's geological history, it said. Additionally, the heat from these formations may create unique marine habitats, "adding another layer to the country's existing environmental conservation efforts in Marae Moana".
Louisa Castledine of Ocean Ancestors, a collective of individuals, NGOs and businesses calling for a moratorium on seabed mining, said that new discoveries like these highlight the expanse of the ocean and the further research required to fully understand the heritage that surrounds the nation.
"Discoveries such as this only further highlights the importance of adopting a moratorium and the need for independent research," Castledine said.
"With so much still unknown about the depths of our oceans, a moratorium would not only safeguard biodiversity, consider the cultural heritage of the seabed, as well as allow for further research and understanding so we can be better informed about how we proceed.
"It's crucial that we prioritise the health of our marine environment over short term extractive industries such as deep-sea mining."
The seabed of the Cook Islands is made mostly of rocks formed from undersea volcanoes of different kinds.
"When we map the seabed in some detail, we discover a landscape of hills, valleys, and plains. Some volcanoes form massive mountains, others that look like pancakes, and others again that sprawl across the landscape. The tallest volcanoes reach above the waves and are often crowned with limestone reefs; of course, these are our islands," SBMA explained.
"While most of these volcanoes are quite old, about 10, 20, 30, or even over 100 million years old, the islands of Rarotonga and Aitutaki are different, as both islands are made of a combination of older and younger volcanic rocks."
The younger rocks are "much younger", according to a geologist, with lavas as young as "only" 1.2 million years old on Rarotonga.
"This is the main reason why Rarotonga at least has such large mountains compared to the other islands. Basically, there hasn't been enough time for the rain and waves to erode all of the volcanic rock into the sea."
According to SBMA, some of the volcanoes in the Cook Islands, including Rarotonga, are believed to form from so-called "hot spots" deep in the earth.
"As the surface of the earth moves due to plate tectonics or continental drift, a string of volcanoes form above the hotspot, a little bit like what would happen if you moved your hand above the top of a candle… The Hawaiian Island chain is the best example of this, and experts like Dr Matthew Jackson, who is with the University of California at Santa Barbara, study these hot spots in the Cook Islands region."
he new bathymetric data of the volcanic chain southeast of Rarotonga. Photo: Cook Islands News / SBMA
Last year, Dr Jackson and his graduate student, Yifan Du, discovered that an underwater volcano (named "Tama"), about 60km south-east of Rarotonga, is half the age of the younger rocks in Rarotonga.
At about 670,000 years old, these are the youngest volcanic rocks yet discovered in our country, SBMA said.
The team noticed that if they drew a line from Rarotonga through Tama and continued southeast, it appeared there might be more volcanoes further along. Using the hotspot model, these could be much younger and potentially even active today. At almost the expected location is another underwater volcano called "Pepe", SBMA said.
"Well, once the team realised this situation was a possibility, we also realised pretty quickly that we didn't have the capability right now to go and search the area to confirm if there was something there. So ... We filed the idea for another time."
About six months later, SBMA got an opportunity to do at least part of the work, and they organised a mini expedition called ARTEX2025. The opportunity arose after the locally based research ship, Kiva Marine's M/V Anuanua Moana, had to leave harbour to make room for an incoming container ship.
From this latest expedition, SBMA discovered: "The new seabed mapping now shows in detail a line of volcanoes on the seabed south-east of Rarotonga."
"In addition to Tama and Pepe, there are smaller volcanic knolls along the line connecting them with Rarotonga and occurring further south-east again," SBMA said.
"These may well have come from a volcanic hotspot based on their shape and location, but samples need to be taken in the future to properly check. Once fully processed and interpreted, our new seabed map should help any future scientists quickly go directly to the best points for this sampling.
"We also now have some water column conductivity and temperature data, but it also needs to be processed and compared to other parts of the Cook Islands to see if it is different in certain key areas.
"So far, we have not seen any clear signs of volcanic activity, but then again, no one has yet had the chance to look carefully at the seabed and sample it."
Additional reporting from SBMA
-This article was first published by Cook Islands News.
