A Hidden Chain of Underwater Volcanoes Discovered Near the Cook Islands

(Image credit: @ Didier Marti/Getty Images)

The vastness of the ocean continues to surprise us with its secrets. In an exciting discovery, researchers have mapped out a never-before-seen chain of underwater volcanoes near the Cook Islands in the Central Pacific. Some of these volcanoes may even be active, potentially fostering a unique marine ecosystem beneath the waves.

The Discovery of the Submerged Volcanoes

The underwater volcanic structures were detected during the ARTEX 2025 expedition, which aimed to map the seafloor southeast of Rarotonga, one of the Cook Islands. This area, located roughly 2,900 miles (4,700 kilometers) south of Hawaii, was previously suspected of hiding volcanic formations. Initial observations suggest that these newly discovered structures are relatively young in geological terms.

“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,” said representatives from the Seabed Minerals Authority (SBMA), which co-led the research. Further analysis of the data collected during the expedition could guide future scientific exploration and sampling efforts.

A Geological Marvel: The Cook Islands and Volcanic Hotspots

The Cook Islands are an archipelago of 15 islands formed millions of years ago due to a magma hotspot beneath the Pacific Plate. Similar to how the Hawaiian Islands were created, a stationary mantle plume beneath the Earth's crust has continuously fed volcanic activity in this region. As the tectonic plate moves, new islands and underwater volcanoes emerge over time.

Hotspots function differently from volcanic activity at tectonic plate boundaries. Instead of forming due to colliding or diverging plates, they remain fixed in position while the Earth's crust slowly drifts over them. This geological process explains why some of the Cook Islands’ volcanoes are much younger than others.

The Youngest Volcanic Rocks in the Cook Islands

Most of the volcanoes in the Cook Islands date back tens or even hundreds of millions of years. However, some islands, like Rarotonga and Aitutaki, contain a mix of older and younger rock formations. Researchers previously discovered that one underwater volcano, named Tama, located about 37 miles (60 km) southeast of Rarotonga, contains rock samples as young as 670,000 years. This discovery sparked curiosity about the presence of additional, younger volcanic structures in the region.

The ARTEX 2025 expedition confirmed these suspicions, revealing a series of smaller seafloor structures stretching southeast from Rarotonga. One of the most notable discoveries is a 0.6-mile-high (1 km) volcano named "Pepe." However, researchers have yet to confirm whether these structures are currently volcanically active.

The Future of Exploration

While scientists have now mapped these underwater volcanoes, much remains to be learned. Future expeditions will focus on collecting rock samples to determine their exact age and studying any potential hydrothermal activity. If these volcanoes are active, they could be playing a crucial role in sustaining unique deep-sea ecosystems.

The discovery of this hidden volcanic chain adds another piece to the puzzle of Earth’s dynamic geology. As technology advances, further oceanic explorations will undoubtedly unveil more of the planet’s underwater mysteries.

What Do You Think?

The deep sea still holds many secrets waiting to be uncovered. What other hidden geological wonders do you think scientists might discover in the future? Share your thoughts in the comments below!