How Deep Is the Deepest Spot in the Ocean?
Off the island of Guam in the Pacific Ocean is a very deep, crescent-shaped trench called the “Mariana Trench.” Near the southern tip of the crescent, there is a small slot-shaped area called the “Challenger Deep.”
Its lowest explored point is 35,797 feet below the ocean’s surface. That’s nearly seven miles, and it is the deepest known spot on the Earth. The Challenger Deep is named after a British Royal Navy ship called the HMS Challenger. The Challenger was the first ship to measure the depths of what is now known as the Challenger Deep.
A steel ball dropped into the water above this spot would take an hour to reach the bottom! Scientists measure the ocean’s depths with a special instrument called an “echo sounder.”
An echo sounder sends sound waves to the ocean bottom, and then measures how long it takes the echo of the sound waves to return to the surface. The trench was measured by “sounding,” which involves dropping a very long line with a weight at the end into a body of water.