Why we map the ocean floor
New technologies are shining light on the long-enduring mysteries of the seabed
You may have heard this fact before: The global ocean covers more than 70 percent of Earth’s surface. Despite its vastness—or rather, because of it—the ocean is essential to life on Earth. You also probably know that the ocean plays a critical role in regulating the planet's health and climate, that it produces a wealth of resources, and that it serves as a superhighway for the global economy. But when is the last time you thought about the ocean floor? Whether we realize it or not, the ocean floor is interwoven with all life on this planet—including yours.
Here in the early 21st century we know less about the ocean floor than we do about the surface of the moon or Mars. To date, barely one-fifth of the seabed has been mapped in high resolution, limiting our collective knowledge and understanding of these watery depths.
Plenty of valid reasons contribute to the lack of consistent, high-quality data about the ocean floor. Namely, the ocean is big, and seabed mapping is notoriously difficult, expensive, and—historically at least—inefficient. Until recently, ocean scientists lacked the tools and resources to pursue seabed mapping at scale. But thanks to rapid advances in mapping technology, and a growing recognition of the seabed’s importance, a comprehensive, high-resolution map of the seabed is within reach. This is a significant milestone because seabed maps can help scientists and economists tackle many of the gravest challenges facing the planet—and its inhabitants—today.
This map, created by Marie Tharp and Bruce Charles Heezen (and hand-painted by Heinrich Berann), is one of the first global seafloor maps. (Source: Library of Congress )
The map above, created in 1977 by geologists Marie Tharp and Bruce Charles Heezen, is one of the first complete representations of the ocean floor. But as detailed as this map appears, it is hardly an accurate depiction of seabed topography. Instead, it is the product of educated guesswork: At the time of the map's creation, reliable seafloor data was scarce.
Today we are still making educated guesses about the ocean floor. But we are also making swift progress toward understanding this abyssal landscape, thanks to emerging technologies and improved data. The series of maps below makes use of an unconventional map projection. The Spilhaus projection "unwraps" the globe in a way that emphasizes the oceans as a single system. With this projection we can more clearly see the big-picture patterns with the data that is available to us.
The global ocean
Today, much of what we think we know about the ocean floor is derived from low-resolution satellite data. While this data isn't suitable to use for serious analysis, it can help us gain an overall understanding of what's below the surface.
Draining the ocean
Concealed beneath this vast body of water is a surface just as diverse and complex as the lands above sea level. We know the seafloor is not smooth, as early oceanographers believed; rather, it is punctuated by mountain ranges, canyons, volcanoes, and other familiar features.
Earth’s undersea landforms aren't just geological curiosities: They provide important clues about the planet's history, health, and prognosis.
Cracks in the basin
Seabed maps reveal that the planet's surface is made up of more than a dozen individual tectonic plates. The plates sit atop Earth’s slowly roiling mantle and fit together like a jigsaw puzzle. However, because the tectonic plates are not fixed in place and are continuously shifting, sliding, and grinding into one another, the seams between these plates, called faults, are often hotspots of geologic activity. Above the water, we often observe the results of the shifting plates in the form of earthquakes and volcanic eruptions.
Perpetual transformation
As these plates are constantly shifting, the seabed is constantly transforming itself where fractures occur. In fact, the seabed is young compared to the rest of the planet. Along the long, sinuous mid-ocean ridges where adjacent plates are slowly moving apart—known as divergent boundaries—magma rises from beneath Earth's crust. As the magma seeps through the gaps between plates, it rapidly cools, creating new seabed.
The oldest parts of the ocean floor are only around 280 million years old, or a faction of the planet's estimated 4.5-billion-year lifespan.
Explosive destruction
Conversely, in places where the plates collide—called convergent boundaries—one plate will often slide under the other. This process, called subduction, produces many of the planet's mountain ranges and volcanoes.
Subduction can be a violent process. It's no coincidence that most undersea earthquakes and volcanoes are concentrated near faults in the seabed. High-resolution seabed maps can help scientists predict catastrophic geologic events before they happen, which may reduce the impact on nearby populations.
This map shows all undersea earthquakes in the last century with a magnitude of 6 or greater.
Quiet giants
Not all undersea mountains—also called seamounts—are violent. For every active volcano on the ocean floor, there are hundreds, even thousands, of inert seamounts.
Undersea mountains are sites of high levels of biodiversity, because their variable elevations create different habitats. Seamounts also play an important role in food production, as many fisheries are located near these biodiversity hotspots.
By cataloging seamounts in high resolution, scientists can develop a clearer picture of life beneath the surface—and by extension, better manage marine fish resources, ensuring that local fish stocks aren't depleted and that food remains affordable to everyday consumers. Other benefits may include better protection for vulnerable species.
Communication connections
The ocean floor isn't home to just plants and animals. More than 1.3 million kilometers (about 800,000 miles) of submarine data and communications cables traverse the seabed, connecting distant continents (and billions of humans) in real time.
Although submarine cables are heavily reinforced, they are still liable to failure—especially when placed on areas of the seabed that are prone to geologic agitation, like near fault lines and volcanoes. Equipped with high-quality seafloor maps, cable-layers can avoid hazardous zones.
High-seas highway
Once a nearly insurmountable obstacle, the ocean is now a critical trade highway for the global economy.
At any given moment, tens of thousands of ships are at sea, many of them transporting consumer goods. As the ocean continues to grow busier, seabed maps will play an increasingly important role in minimizing environmental issues caused by damaged or disabled sea vessels, and help mitigate risks for logistical and infrastructure that connect to world economic and supply chain.
These aren’t the only reasons for mapping the seabed. As the world population grows, our demands for energy also grow. It’s increasingly important to have accurate maps for energy resources, including oil pipelines, offshore drilling areas, and wind turbines, to understand how these energy and economy sectors interact with all the other forms of marine activity.
Looking to the future
As of 2022, a little more than one fifth of the seabed has been mapped in high resolution—and that number is increasing every year. The technology needed to map the ocean floor is becoming more accessible, and initiatives like the Seabed 2030 Project—which aims to map 100 percent of the ocean floor in high resolution by 2030—are coordinating and consolidating new data as it comes in from contributors around the world. Yet, the map below makes it evident that there remain great swathes of the ocean floor about which we know next to nothing.
Left: Areas mapped in low resolution. Right: Areas mapped in high resolution. (Source: GEBCO )
The ocean floor has much to teach us. By obtaining a clear, consistent picture of the seabed, we can capitalize on the lessons about our planet that await deep below the ocean's surface.
Collecting data about the ocean floor enables us to anticipate natural disasters like earthquakes, volcanoes, and tsunamis, and mitigate their effects. This information can improve our understanding of undersea habitats and equip us with the tools to make informed decisions about marine conservation. It can help us identify and locate economically valuable resources and ensure they are explored and extracted sustainably. And, it can help us build and maintain essential undersea infrastructure, like submerged telecom cables, with minimal impact to natural habitats.
As humankind continues to explore the ocean, we can only guess what new discoveries we will make. And we have yet to see how these discoveries will impact our everyday lives. But we are making swift progress, and the answers may arrive sooner than we expect.
