Oceans cover how much of the earth

This site uses cookies to assist with navigation, analyse your use of our services, collect data for ads personalisation and provide content from third parties. By using our site, you acknowledge that you have read and understand our Privacy Policy and Terms of Use. Share Twit Share Email. Home Earth Earth Sciences. Earth — Western Hemisphere. Many theories about the origins of water on Earth attribute it to collisions with comets and asteroids. More information: water.

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You cannot download interactives. Marine ecosystems contain a diverse array of living organisms and abiotic processes. From massive marine mammals like whales to the tiny krill that form the bottom of the food chain, all life in the ocean is interconnected.

While the ocean seems vast and unending, it is, in fact, finite; as the climate continues to change, we are learning more about those limits. Explore these resources to teach students about marine organisms, their relationship with one another, and with their environment. Explorer-in-Residence Enric Sala reviews general facts about each ocean within the one world ocean.

Join our community of educators and receive the latest information on National Geographic's resources for you and your students.

Skip to content. Image Ocean Waves The ocean covers more than 70 percent of Earth, and more than 80 percent of it remains unexplored. Photograph by Getty Images. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Things would get pretty stale without the water cycle! The globe illustration shows blue spheres representing relative amounts of Earth's water in comparison to the size of the Earth.

Are you surprised that these water spheres look so small? They are only small in relation to the size of the Earth. This image attempts to show three dimensions, so each sphere represents "volume.

The smaller sphere over Kentucky represents Earth's liquid fresh water in groundwater, swamp water, rivers, and lakes. The volume of this sphere would be about 2,, mi 3 10,, km 3 and form a sphere about Yes, all of this water is fresh water, which we all need every day, but much of it is deep in the ground, unavailable to humans. Do you notice the "tiny" bubble over Atlanta, Georgia?

That one represents fresh water in all the lakes and rivers on the planet. Most of the water people and life on earth need every day comes from these surface-water sources. The volume of this sphere is about 22, mi 3 93, km 3. The diameter of this sphere is about Yes, Lake Michigan looks way bigger than this sphere, but you have to try to imagine a bubble almost 35 miles high—whereas the average depth of Lake Michigan is less than feet 91 meters.

The vast majority of water on the Earth's surface, over 96 percent, is saline water in the oceans. The freshwater resources, such as water falling from the skies and moving into streams, rivers, lakes, and groundwater, provide people with the water they need every day to live. Water sitting on the surface of the Earth is easy to visualize, and your view of the water cycle might be that rainfall fills up the rivers and lakes. But, the unseen water below our feet is critically important to life, also.

How do you account for the flow in rivers after weeks without rain? In fact, how do you account for the water flowing down a driveway on a day when it didn't rain? The answer is that there is more to our water supply than just surface water, there is also plenty of water beneath our feet.

Even though you may only notice water on the Earth's surface, there is much more freshwater stored in the ground than there is in liquid form on the surface. In fact, some of the water you see flowing in rivers comes from seepage of groundwater into river beds. Water from precipitation continually seeps into the ground to recharge aquifers , while at the same time water in the ground continually recharges rivers through seepage. Other fodder for sea dwellers includes seaweed and kelp, which are types of algae, and seagrasses , which grow in shallower areas where they can catch sunlight.

The deepest reaches of the ocean were once thought to be devoid of life, since no light penetrates beyond 1, meters 3, feet. But then hydrothermal vents were discovered. These chimney-like structures allow tube worms, clams, mussels, and other organisms to survive not via photosynthesis but chemosynthesis, in which microbes convert chemicals released by the vents into energy.

Bizarre fish with sensitive eyes, translucent flesh , and bioluminescent lures jutting from their heads lurk about in nearby waters, often surviving by eating bits of organic waste and flesh that rain down from above, or on the animals that feed on those bits. Despite regular discoveries about the ocean and its denizens, much remains unknown. More than 80 percent of the ocean is unmapped and unexplored , which leaves open the question of how many species there are yet to be discovered.

At the same time, the ocean hosts some of the world's oldest creatures: Jellyfish have been around more than half a billion years , horseshoe crabs almost as long. Other long-lived species are in crisis. The tiny, soft-bodied organisms known as coral , which form reefs mostly found in shallow tropical waters, are threatened by pollution, sedimentation, and global warming.

Researchers are seeking ways to preserve fragile, ailing ecosystems such as Australia's Great Barrier Reef. Human activities affect nearly all parts of the ocean. Lost and discarded fishing nets continue to lethally snare fish , seabirds, and marine mammals as they drift. Ships spill oil and garbage; they also transport critters to alien habitats unprepared for their arrival, turning them into invasive species.

Mangrove forests are cleared for homes and industry. Our garbage— particularly plastic —chokes the seas, creating vast " garbage patches " such as the Great Pacific Garbage Patch. Fertilizer runoff from farms turns vast swaths of the ocean into dead zones, including a New Jersey-size area in the Gulf of Mexico. Climate change , the term scientists now use to describe global warming and other trends currently affecting the planet because of high greenhouse gas [1] emissions from humans, is strikingly reflected in the oceans.

The greenhouse gas carbon dioxide is also turning ocean waters acidic, and an influx of freshwater from melting glaciers threatens to alter the weather-driving currents: the Atlantic Ocean's currents have slowed by about 15 percent over the past few decades.