Saturday June 08, 2013 | 10:10 AM
Posted by Harold Johnson

Today, June 8th, marks the 5th annual official “World Oceans Day.” To mark the occasion, a brief list of the things you may not know about the ocean.

* Oceans cover 71% of the planet. Combined, the ocean contains about 324 million cubic miles of water, 97% of the water on earth.

* The average depth of the world’s oceans is 14,000 feet -- 2 ½ miles. (The average height of all the landmasses on earth is 2,700 feet, about ½ mile.)

* At least 50% of the oxygen that we breathe comes from phytoplankton -- microscopic algae -- in the world’s oceans. Take a breath, now take another. Every second breath you take throughout your whole life is thanks to the ocean.

(Plankton bloom seen from space; Source

* Without the oceans to absorb & transport the sun’s heat, the equator would broil and everywhere else would be frigid cold. Life as we know it could not exist.

* The highest tides in the world lie within Mainers’ reach, at the Bay of Fundy. At certain times of year they can vary ~50 feet between low and high tide! (Here’s a timelapse of Hall’s Harbour.)

(Credit: Samuel Wantman, 1972)

* There are 202,388 verified species of lifeforms in the world’s oceans. This number probably represents only 1/10 of the actual total.

* The Gulf of Maine has ~3,000 known species of marine life.

* Earth’s longest mountain range is under the ocean, the Mid-Ocean Ridge, a connection of volcanic mountains rising from the seafloor, circling the earth and running for more than 40,000 miles.

* The deepest place in the world is in the western Pacific ocean, Challenger Deep in the Mariana Trench. There, the seafloor lies 36,000 feet down. If you nestled Mt. Everest into Challenger Deep, its peak would still be more than a mile below the waves.

* The deepest spot in the Gulf of Maine is in George’s Basin, a depth of 1200 feet.

* The water pressure at Challenger Deep is equivalent to one person trying to support 50 jumbo jets on their head. Yet there is life there.

* Every ocean has a gyre, or a slowly turning vortex of water, in its central area -- sometimes a thousand miles across. Every gyre has plastic floating in it.

(Captain Charles Moore holds a sample of seawater trawled from the Pacific; Source; credit: Matt Cramer for Algalita Marine Research Foundation)

* The world’s fisheries caught the most sealife in 1989 -- 90 million tons. Since then the numbers have dropped even as fishing effort intensifies. A 2003 report estimated that 90% of the large fish in the world’s oceans were gone.

* More people have set foot on the moon than have visited the deepest place in the ocean.

* Only 5-10% of the ocean floor has been mapped. The rest remains a mystery.

We rely more & more on the oceans of the world. And we’re putting an ever-increasing burden on them. Yet we still understand so little about them. So it’s amazing that, in 2013, the Undiscovered Country begins still right off our shores. And any one of us can start to explore it, tell its stories, and protect its future. And our future as well.

Happy World Oceans Day. 

About this Blog

Subscribe to
Undercurrents RSS

About the Author

Visiting a Maine beach in March 2010, Harold Johnson was shocked by the ocean-borne debris left by recent storms. He grabbed a garbage bag and a camera, and hasn’t looked back.

Since then he has spent most of his free time studying marine pollution, coastal ecosystems, and the mysteries and science of ocean and shore.

Copyeditor and writer by trade, historian and archaeologist at heart, Johnson’s philosophy is simple: Dig below the surface, travel the currents, make the connections, learn. Then share what you learn. He lives in Saco with his wife and young daughter. Follow on Twitter @FlotsamDiaries.

Previous entries

March 2014

February 2014

January 2014

December 2013

November 2013

October 2013


September 2013

August 2013

July 2013

June 2013

May 2013

April 2013

March 2013

February 2013

January 2013

Further Discussion

Here at we value our readers and are committed to growing our community by encouraging you to add to the discussion. To ensure conscientious dialogue we have implemented a strict no-bullying policy. To participate, you must follow our Terms of Use.

Questions about the article? Add them below and we’ll try to answer them or do a follow-up post as soon as we can. Technical problems? Email them to us with an exact description of the problem. Make sure to include:
  • type of computer or mobile device your are using
  • exact operating system and browser you are viewing the site on (TIP: You can easily determine your operating system here.)
Prefer to respond privately? Email us here.