Seamounts: Mountains of the Deep

Some of the largest mountains on Earth lie beneath the ocean’s surface. Seamounts, underwater mountains formed by volcanic activity, rise thousands of meters from the seafloor but remain fully submerged. Many are found along mid-ocean ridges, the world’s longest mountain ranges, and are foundational to ocean life: influencing currents, biodiversity, ecosystems, and the movement of organisms across vast distances. 

Seamounts typically rise 1,000 to more than 4,000 meters above the ocean floor, comparable in height to major mountain ranges on land. Their bases often sit 3,000 to 6,000 meters below the surface, while their peaks remain fully submerged. If these underwater mountains were lifted onto land, they would rank among the most imposing geological features on Earth, rivaling the height and mass of The Rocky Mountains or The Alps. 

Scientists estimate there may be 30,000 to 100,000 seamounts worldwide. Yet fewer than ten percent have been mapped in high resolution, and far fewer have been studied biologically. This lack of knowledge limits how effectively these ecosystems can be considered in ocean management and protection. OceanX is changing this by making information about seamounts more accessible, one mission at a time. 

How Seamounts Influence the Ocean 

Seamounts shape ocean life by influencing water movement. As large currents encounter steep underwater terrain, water is deflected upward along the slopes of these mountains. This process transports nutrients from deep water into more productive layers of the ocean, fueling plankton growth—the base of marine food webs. 

As a result, seamounts often support dense and diverse ecosystems. Their rocky slopes provide habitat for corals and sponges that can live for centuries. Fish, sharks, and other predators aggregate to feed, while highly migratory species return to seamounts repeatedly as they move across the open ocean. These underwater mountains act as ecological connectors, linking distant regions through both physical currents and biological movement. 

Because of this, protecting seamounts has impacts well beyond the mountains themselves. Their health influences fisheries, biodiversity, and ecosystem balance across entire ocean basins. 

Mapping Seamounts: Building the Foundation for Protection 

Mapping is the essential first step in understanding seamounts. High-resolution seafloor maps reveal their true shape, size, and complexity—details that cannot be captured by satellites alone. Without this information, seamounts may appear only as vague outlines or remain entirely unmapped, leaving critical habitats invisible in conservation planning. 

OceanX maps seamounts using advanced multibeam sonar aboard OceanXplorer, creating detailed three-dimensional images of underwater terrain. These maps reveal steep ridges, plateaus, and valleys that shape how water moves and where life thrives. Mapping provides context for every scientific observation that follows, helping researchers understand why species gather in certain locations and how physical structure supports entire ecosystems. 

From Mapping to Living Systems 

Once a seamount is mapped, scientists can explore it directly. Submersibles and remotely operated vehicles are used to observe habitats in real time, document species, and collect samples. Environmental DNA (eDNA) sampling adds another layer, allowing scientists to identify organisms present in the water. 

This integrated approach has guided OceanX expeditions around the world. During the Azores Mission (2023), OceanX worked with Portuguese scientists to map nearly 4,220 square kilometers of seafloor, including areas that had never been surveyed before. Dives revealed deep-sea coral gardens, sponge fields, and steep seamount slopes shaped by volcanic and tectonic forces. Crucially, the data contributed to the designation of seamount-focused marine protected areas in the Azores, showing how exploration can directly inform conservation policy. 

Similarly, mapping at the Nola Seamount Complex near Cabo Verde (2025) produced one of the most detailed digital profiles of a seamount system to date. By combining bathymetric maps with biological observations from deep abyssal slopes to shallower summits, scientists gained insight into how ecosystems change with depth and terrain—information essential for spatial planning and protection. 

In the eastern Indian Ocean, the Monsoon Rise expedition (2025), conducted with the National University of Singapore (NUS) and scientists from across Southeast Asia and the Pacific, mapped 8,330 square kilometers, including 5,921 square kilometers of previously unexplored seafloor. This work established the first comprehensive biodiversity baseline for an entire seamount chain in areas beyond national jurisdiction, supporting future conservation under the UN High Seas (BBNJ) Agreement. 

“OceanXplorer was designed as a platform to unite exploration, science, media, and education. Partnering with NUS on this mission allows us to expand knowledge of one of the last great unknowns of our planet and inspire people across Asia and the world to protect it,” said Mark Dalio, founder and co-CEO of OceanX. 

Most recently, on December 2, 2025, OceanX set sail with Indonesia’s national research agency, BRIN, on a new expedition into the seamounts carved by The Pacific Ring of Fire. The team is combining detailed seafloor mapping with biodiversity research and capacity building, helping to expand regional scientific capabilities while revealing how life thrives in one of Earth’s most active geological corridors. 

Why This Work Matters Now 

Seamount ecosystems are increasingly exposed to pressure from fishing, climate-driven changes in ocean temperature and chemistry, and expanding human activity in the deep sea. Many species associated with seamounts grow slowly and live long lives, making them especially vulnerable to disturbance.  

Mapping and documentation allow scientists and stakeholders to move from uncertainty to evidence. They turn unknown terrain into defined ecosystems that can be monitored, managed, and protected before irreversible damage occurs. 

Looking Ahead 

Seamounts are not isolated features: They are central to how the ocean circulates, feeds life, and connects ecosystems across thousands of kilometers. Yet many remain uncharted. 

By integrating exploration, mapping, science, and education, OceanX works to ensure that these underwater mountains are understood and accounted for in decisions about the ocean’s future. Each expedition adds clarity where there was once uncertainty, helping build the knowledge needed to protect seamounts and the ocean systems they sustain for generations to come.