Moment of Science: Ocean Depth

“This is my church. Down here you feel the power of nature’s imagination, which is so much greater than our own.” -James Cameron
Humans have been sailing across the sea for centuries... yet we've barely begun to map what lies beneath. 🌊🔻
Published: Nov. 8, 2022 at 1:13 PM EST
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Space may be the final frontier, but there is so much unexplored territory beneath the waves on the ocean! Let’s take a dive into how deep the ocean really is.

* The vast majority of marine life lives in the “euphotic zone” -- basically from the surface to 200 meters (~650 ft) deep. That’s where you’re most likely to still have sunlight penetrating through the water -- good news for plankton and algae, which produce a good half of our atmosphere’s oxygen. Sharks, dolphins, whales, even jellies are usually within that zone -- but it’s by no means a cutoff point. Great Whites, swordfish, even some Emperor penguins have been discovered diving to about the 500-meter mark.

* We’ve now crossed over into... The Twilight Zone (200m-1000m / 650-3300 ft). This is where you start to lose light, and where certain species have developed bioluminescence to help see in the dark. (We’ll cover them in a later episode.) The deepest human scuba dive comes in at a mere 332 meters (1090 ft), and many military submarines max out around double that depth. For comparison, certain crabs and octopi can be found around there, and even leatherback sea turtles can dive up to the 1000-meter mark.

* Enter “The Midnight Zone” (1000-4000m / 3300-13000 ft): No sunlight, and therefore no plants... just the occasional anglerfish or blobfish vying for the top prize in the beauty contest. The “colossal squid” isn’t just a myth, though they are incredibly rare -- and with such low light in this zone, have developed the largest eyes of any creature in existence (27cm / 10.6 in)... all the better to see Captain Nemo with. The Cuvier’s beaked whale is the deepest diving mammal at 3000 meters (10,000 ft), and the Titanic’s final resting place is about 800 meters down from that. Believe it or not, we’re at the AVERAGE ocean depth... so let’s speed this up.

* Now we’re in the “Abyssopelagic Zone” (4000-6000m / 13,000-20,000 ft) -- yep, it’s where we get “the abyss” from. Temperatures are barely above freezing, and there’s barely any sustained life that can take the pressure. Mount Everest? Shorter. Cruising altitude? Keep going. We finally arrive at the deepest known part of the ocean: “Challenger Deep” in the Mariana Trench (10,908m / 35,787 ft), with 8 tons of pressure per square inch pressing on the hull -- over 1000 times what’s acting on you right now. Only three humans have reached this point on Earth: U.S. Navy Lt. Don Walsh and oceanographer Jacques Piccard in 1960, and filmmaker James Cameron in 2012.

* Note that we said the deepest KNOWN part of the ocean. NASA estimates we’ve only mapped between 5 to 15% of our sea floor... that means we have better maps of the surface of Mars, than we do 70% of our own planet!

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