In instances where the submarine volcanoes are located close to human-populated shorelines, eruptions can become hazardous, placing local human populations at risk. The same risks may also apply to areas with high maritime traffic, placing boats, their cargo, and their crew at risk when near an erupting volcano. Many submarine vessels have also collided with submarine volcanoes, sometimes resulting in injury or death of crew members.

Additionally, what makes submarine volcanoes unique is that their eruptions have the potential to form volcanic islands, unlike terrestrial volcanoes. Islands can form from submarine volcanic eruptions because the passive lava flows sometimes build up the height of the submarine volcano, allowing it to reach the ocean surface. However, these volcanic islands are sometimes temporary due to erosion. Such temporary islands are known as ephemeral islands.

Recent Events

Similar to low-scale seismic earthquakes, submarine volcanoes are erupting on a regular basis and oftentimes without much warning. On October 21, 2023, an unnamed volcano off the coast of Iwo Jima in Japan began erupting, eventually forming a new island of about 100 meters, or 328 feet, in diameter as of October 30, 2023, according to the Earthquake Research Institute at the University of Tokyo. Interestingly, the island of Iwo Jima itself is a volcano. While Iwo Jima is not a submarine volcano, the recent submarine volcanic eruptions were on the flank of the ‘parent’ volcano of Iwo Jima. According to Setsuya Nakada, a professor with the Earthquake Research Institute at the University of Tokyo, as volcanoes erupt, “it’s hard to know when it will stop, but assuming the eruption continues, the [resulting] island could grow higher and bigger.” Later reports did state that, once the volcanic activity subsided in early November, the newly formed island does not appear to be durable, as the material composition of the lava was “crumbly.” 

The Japan Meteorological Agency estimates there are around 111 active volcanoes in Japan, including submarine varieties. In recent history, submarine volcanoes have erupted before in and around Japan. In 2013, an eruption occurred within the island chain of Nishinoshima—located south of Tokyo—in the Pacific Ocean. The result was an island that has lasted for around a decade so far. In 2021, the same submarine volcano as the one that erupted in October 2023 near Iwo Jima experienced a major undersea eruption, further exemplifying the higher levels of activity in this particular region.

Notably, several terrestrial volcanoes were erupting at the same time as the submarine volcano in Japan, including the Klyuchevskaya Sopka volcano in Russia, Mount Etna in Italy, and Mount Mayon in the Philippines. According to experts at the Smithsonian Institution’s Global Volcanism Program, the number of coinciding eruptions is normal. 

Keep In Mind

People often become aware of submarine volcanoes through their eruptions and prepare against the high risks of volcanic eruptions by tracking said eruptions.. Thus, the current lack of knowledge on submarine volcanoes lends to a dangerous situation and is concerning.

Eruptions of submarine volcanoes can lead to loss of life, among other kinds of devastation. In January of 2022, a submarine volcanic eruption in the nation of Tonga resulted in three deaths. In an incident that rivaled the Krakatoa Island eruption of 1883, a sonic boom produced by the eruptions was heard all the way in New Zealand, which lies 1,300 miles away. The eruption of lava into the ocean also resulted in a tsunami stretching up to 65 meters high that struck the main island of Tonga. Resulting smaller waves were also recorded as reaching the shorelines of Japan, Australia, the U.S., and Chile.

The submarine volcano central to this 2022 explosion, the Hunga Tonga-Hunga Ha’apai volcano, was small and unknown before the eruption. Given the small amount of research dedicated to submarine volcanoes, such an explosion highlights the need for further investigation. While the likelihood that submarine volcanic eruptions can pose a severe risk to humans is small, some instances have proven to be catastrophic and far-reaching. According to experts at the University of Hawaii, there are currently dozens of submarine volcanoes around the world that could erupt like Hunga, potentially claiming thousands of lives and even reshaping coastlines.

There are scientists already paying attention to the importance of tracking submarine volcanoes. In April 2023, a new seamount catalog was published that used data collected from radar satellites. Yet, there is still more to be done. While the catalog detected more than 43,000 submarine volcanoes in the Earth’s waters, only 16,000 have been charted in detail by sonar tools. Sonar research must be conducted on the topic of submarine volcanoes, detailing the size and locations of these submarine volcanoes. Perhaps this topic of research could be a joining point for cross-national cooperation, such as between the U.S. and Chinese navies who recently re-established regular lines of communication. Even in an era of increased tension over submarine activity, a joint scientific venture to study and map the submarine volcanoes that may pose a threat to not only submarine vessels but to humanity at large could become a collaborative partnership.

This issue’s Spotlight was written by Jacqueline Cheng, Part-Time Research Assistant Intern