How much of the ocean has been explored?

While approximately 20% of the seafloor has been mapped to modern standards, only about 5% of the ocean has actually been explored.

Sometimes menacing, sometimes serene, there’s still so much to be learned about our ocean and what lies beneath its surface. Image courtesy of Art Howard, Global Foundation for Ocean Exploration, NOAA Office of Ocean Exploration and Research, 2019 Southeastern U.S. Deep-sea Exploration.

Sometimes menacing, sometimes serene, there’s still so much to be learned about our ocean and what lies beneath its surface. Image courtesy of Art Howard, Global Foundation for Ocean Exploration, NOAA Office of Ocean Exploration and Research, 2019 Southeastern U.S. Deep-sea Exploration. Download image (jpg, 9.9 MB).

The ocean covers approximately 70% of Earth’s surface. It’s the largest livable space on our planet, and there’s more life there than anywhere else on Earth. But, there’s still much we don’t know about the ocean, and there’s not a straight-forward answer to the question about how much has been explored. It’s usually answered in two ways: percentage of the ocean explored and percentage of the seafloor mapped. The answers aren’t the same.

First, consider the size of the ocean. Its surface area is about 360 million square kilometers (139 million square miles), and its average depth is 3,682 meters (12,080 feet). Importantly, throughout these depths, there is life.

An often quoted statistic suggests that only about 5% of the ocean — the water column and the seafloor — has been explored. Through exploration, we learn more about the biological, chemical, physical, geological, and archaeological aspects of the ocean. Exploration leads to discovery, but before we can truly explore, we must map.

Seafloor mapping provides a sense of what may lie beneath and guides decisions about where to explore (e.g., deploy submersibles, like remotely operated vehicles). While the entire seafloor has been mapped using data collected from satellites, these data provide only a general picture of what’s there. Detail is limited on these maps, so some important geographical features (like seamounts) and objects (like shipwrecks) remain unseen.

By 2020, less than 20% of the global seafloor had been mapped with modern high-resolution technology (multibeam sonar systems), usually mounted to ships, that can reveal the seafloor in greater detail. While almost 50% of the seafloor beneath U.S. waters had been mapped to these modern standards, the nation’s seafloor is larger than the land area of all 50 states, the District of Columbia, and the five territories combined. Thus, there’s still a significant amount of seafloor left to be mapped at high resolution.

More is known about the seafloor than the species that call the ocean home. Seafloor maps can provide information about potential habitats, but they can’t identify species or provide information about how they interact with each other and their environments. Scientists estimate there may be between 700,000 and 1 million species in the ocean (excluding most microorganisms, of which there are millions). Roughly two-thirds of these species, possibly more, have yet to be discovered or officially described, with almost 2,000 new species accepted by the scientific community each year.

We have a great deal more to learn about our ocean and what resides within it, but progress IS being made. We learn more and more each year. We continue to discover new features and creatures, clues to our past, and resources that can improve our future. But the ocean will never be fully explored. Earth is constantly changing, and it’s important to understand these changes given the importance of the ocean in our everyday lives.

However you choose to look at it, about 5% of the ocean explored or less than 20% of the seafloor mapped, the majority of our ocean and its seafloor are largely unknown. That means there’s a lot of work to be done. It also means there’s so much more to discover!