How Deep Is the Ocean

The ocean is the large body of salt water that covers most of Earth's surface. The ocean is not just wide—it is also incredibly deep. Understanding how deep the ocean is helps us realize just how much water it holds.

On average, the ocean is about 12,100 feet deep. To picture this, imagine stacking 40 tall buildings on top of each other! That's how far down the ocean floor—the bottom of the ocean—sits below the surface. Some parts of the ocean are shallow near the coasts, but other areas drop down much, much deeper.

The deepest spot in the entire ocean is called the Mariana Trench, which is a long, narrow valley on the ocean floor in the Pacific Ocean. The Mariana Trench reaches nearly 36,000 feet below the surface. This is deeper than Mount Everest, the tallest mountain on Earth, is tall! If you could place Mount Everest inside the Mariana Trench, the mountain's peak would still be more than a mile underwater.

The ocean holds an enormous amount of water because it is both wide and deep. When we measure the volume of the ocean—the amount of space the water takes up—we find that it contains about 97% of all the water on Earth. This huge volume exists because the ocean spreads across such a large area and extends so far down below the surface.

Scientists use special tools to measure ocean depth. They send sound waves down to the ocean floor and measure how long it takes for the sound to bounce back. This helps them create maps of the ocean floor and discover underwater mountains, valleys, and trenches. Learning about ocean depth helps us understand Earth's water systems and the amazing creatures that live in the deep sea.

Interesting Fact: If you could drain all the water from the ocean, you would see underwater mountain ranges taller than any mountains on land, along with deep canyons and vast flat plains!