The deepest part of the ocean is about 36,000 feet down, in the Mariana Trench. That is nearly 7 miles. The ocean's average depth is about 12,100 feet.
On this page: how deep the ocean is, what sits on the seafloor, why the water is salty, and how much of Earth it covers.
Read the answer below. In Giant, kids talk with characters and keep the adventure going.
The ocean is not a swimming pool with one depth. Shelves near land can be a few hundred feet. Wide plains sit about two to three miles down. Trenches cut much deeper. The record is Challenger Deep in the Mariana Trench, in the western Pacific. It is about 36,000 feet, nearly 7 miles. Mount Everest could sink there and still have water above the peak. The worldwide average is about 12,100 feet. That is still a long elevator ride.
•Most of the ocean is a few miles deep, not a few feet.
•The Mariana Trench holds the deepest known spot.
•Average depth is about 12,100 feet.
~36,000 ft
Challenger Deep
~12,100 ft
Average depth
71%
Earth covered
Pacific
Deepest ocean
What's at the bottom of the ocean?
The deep seafloor is mostly cold mud, rock, and mineral vents, not a sunny beach. Near land, the continental shelf is a shallow step with sand, mud, and sunlight-fed life. Farther out, the abyssal plains are the wide, dark, dusty floors under huge pressure. Trenches cut deeper still. Chimneys called hydrothermal vents spit hot mineral water. Some animals live on chemicals from those vents, not on sunlight. Special vehicles, not swim fins, go there.
•Shallow floors can be bright and busy.
•Deep plains are dark, cold, and under huge pressure.
•Vents feed animals that do not need sunlight.
Why is the ocean salty?
Rain and rivers dissolve minerals from rocks and carry them to the sea. Undersea vents add more. The leftover mix is mostly sodium and chloride, the same ions as table salt. Freshwater stays in lakes because it keeps flowing out. The ocean keeps the salt while water evaporates back into the sky. Over millions of years, that made seawater taste like salt.
How much of Earth is covered by ocean?
About 71 percent of Earth's surface is ocean. The Pacific is the biggest and, on average, the deepest. All that water is one connected system with different names on the map. It stores heat, makes weather, and is home to most of the living space on the planet. Land is the smaller piece of the puzzle.
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