The Texas-sized Great Barrier Reef is the largest living structure on Earth. It's so large, it can be seen from the Moon. The Great Barrier Reef is so diverse, it contains 134 species of sharks alone. Although the most famous reef, the Great Barrier Reef is not the only one. While reefs account for less than 0.1 percent of the ocean surface, they're home to 25 percent of ocean species. Most reefs are located less than 164 feet (50 meters) below the surface.
Everyone knows the world's tallest mountain: Mount Everest. Standing at 29,029 feet (8,848 meters), Mount Everest goes as high as commercial jets do. Mount Everest is so tall that the oxygen at the top is 33 percent what it is at sea level. Yet did you know that Mount Everest really isn't the tallest mountain in the world? That honor truly belongs to Muana Kea in Hawaii. Looking at Muana Kea, it stands at a mighty 13,803 feet tall. So how is this "dormant" volcano taller than Mount Everest? Well it's because most of Muana Kea is hidden under the Pacific Ocean. Mount Everest is based on land, but Muana Kea is based on the sea floor. When taking this into account, the total height of Muana Kea is around 33,500 feet (10,210 meters), which would make it nearly a mile higher than Mount Everest.
Muana Kea is so high, 7 Burj Khalifas (world's tallest building) or 16 Empire State Buildings stacked on top of each other still wouldn't reach the ocean surface. Muana Kea in total is the height of a little over 12 Burj Khalifas, or 27 Empire State Buildings. That shows just how deep the ocean gets - but it gets deeper.
The deepest place on Earth is the Mariana Trench. The Mariana Trench is a 1,580 mile (2,550 kilometers) long trench stretching across the Pacific Ocean floor. The very deepest point is Challenger Deep, a depression in the trench that has a depth between 35,814 and 36,072 feet. That's 6.7 to 6.8 miles deep. If you were able to drive from the ocean surface to Challenger Deep going city highway speeds, it would take you around seven and a half minutes to go from surface to floor. You would run out of noticeable sunlight before you were even 700 feet down.
Mountain ranges dot our landscape. The Rockies, Himalayas, Cascades, Alps, Andes, Ural, Carpathian, the list goes on. These mountains are clearly visible to us, unlike underwater mountains. It's hard to think of jagged mountains being underwater. We tend to the think of the ocean floor sloping until it reaches a smooth bottom, like a bathtub of sorts, but it turns out that the ocean floor can be as smooth as a pile of bricks. The longest known mountain chain in the universe is located under the ocean. While the Grand Canyon is well, grand, there's an even grander canyon underwater called Monterey Bay Submarine Canyon - holding more volume and depth. Our land museums house millions of amazing artifacts of history, but more are hidden in the museum called the "oceans." Just think of all the artifacts that have gotten lost at sea or to the sea over centuries, including the Titanic. Which museum do you see it hanging in, hmm?
Underwater volcanoes and hotspots are plentiful as well. Yellowstone, Krakatoa, Mount Saint Helens, Pompeii, and Vesuvius tend to get all the fame, but what about the underwater volcanoes that gave birth to Hawaii, Indonesia, the Alaskan island chain, the Polynesian islands, and others? This is a process that has been going on since plate tectonics began, and still goes on today. The Hunga Tonga volcano in the South Pacific Ocean formed a new island last year. The island is long enough that you could fit the Empire State Building across it and still have some room left. Another underwater volcano has given Japan some new real estate. Formally called "Snoopy Island" because it resembled the famous Peanuts character, the island, with the volcano now above the surface, is still expanding.
Just like the atmosphere, the ocean has layers, or zones. The Epipelagic Zone is where the vast majority of sunlight and known sea creatures live. The Mesopelagic Zone is commonly referred to as the "twilight zone" because this is where sunlight is at it's faintest and bizarre looking fish begin to appear. The Bathypelagic Zone contains no sunlight or plant life. The only light you'd see is the light given off by bioluminescent fish. The Abyssopelagic Zone contains near freezing temperatures, intense pressure, invertebrates, and 3/4 of the ocean floor. The last but not least zone is the Hadalpelagic Zone (which means "hellish") where ocean trenches and canyons reside, but not much else. The pressure in this zone can equal the weight of 48 Boeing 747's.
Underwater mountains, volcanoes, reefs, sunken ships, and even fish that glow in the dark. There's enough water in the ocean to fill 342,670,000,000,000,000,000 (342 quintillion) gallon milk jugs, so it shouldn't be surprising that there's so much under the surface.
Oh yeah, and there's Atlantis.
*Alan Arnett, Business Insider, NOAA, BBC, National Geographic, Sea and Sky, Adducation, Coastal Challenges, Australia, World Wild Life, Genetic Literacy Project, Arcadis, Mother Earth News, Untamed Science, SquareSpace.