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Making Waves: Episode 89 (January 12, 2012)

You're listening to Making Waves from NOAA's National Ocean Service. I'm Troy Kitch.

I thought I’d kick off the New Year with something a little different for this episode. Today, we’re going to highlight our Ocean Facts. What? Haven’t heard of our famous Ocean Facts? Well, I don’t know how famous they are … but they are quite popular with visitors to the National Ocean Service website. Right now we have over 180 facts about our ocean, and the list is growing every week. Now, these aren’t simple one-sentence answers to ocean questions. Each Ocean Fact provides a detailed answer to a specific question like ‘why is the ocean blue’ or ‘what’s the difference between tides and currents,’ each fact is accompanied by an image or two (a few even have movies), and each fact has links to other sites  you can get more information.

You’ll find facts about ocean life, geology, health, transportation, ocean observation, and ocean management … so if you’re interested in the ocean, studying the ocean, or have a specific question you’d like to answer about the ocean … chances are you’ll find a fact to get you started on our website at And if you don’t find the answer you’re looking for? Send an email to and we’ll add it to the list.

So … to give you a taste of what you’ll find on our site, here are the top five most-popular Ocean Facts as determined by visitors to our site.  Keep in mind that I’m only going to give you the bare-bone answers to these questions. Don’t forget that you can read the full answers to these and all of our Ocean facts at more at And we even have a syndicated feed for you to subscribe to so you’ll always be alerted when we launch a new one. OK, here we go.

Number Five: What’s the different between a dolphin and a porpoise?

People use the terms dolphins, porpoises, and whales to describe marine mammals belonging to the order Cetacea and many often use these terms interchangeably. The orca, or killer whale, for example, is actually the largest member of the dolphin family.

Dolphins are by far more prevalent than porpoises. Most scientists agree that there are 32 dolphin species (plus five closely related species of river dolphin) and only six porpoise species.

So what’s the difference? It essentially comes down to their faces, their fins, and their figures. Dolphins tend to have prominent, elongated “beaks” and cone-shaped teeth, while porpoises have smaller mouths and spade-shaped teeth. The dolphin’s hooked or curved dorsal fin (the one in the middle of the animal’s back) also differs from the porpoise’s triangular dorsal fin. Generally speaking, dolphin bodies are leaner, and porpoises’ are portly.

Dolphins are also more talkative than porpoises. Dolphins make whistling sounds through their blowholes to communicate with one another underwater. Scientists are pretty sure that porpoises do not do this, and some think this may be due to structural differences in the porpoise’s blowhole.

Dolphins and porpoises have many similarities, one of which is their extreme intelligence. Both have large, complex brains and a structure in their foreheads, called the melon, with which they generate sonar (sound waves) to navigate their underwater world.

Number Four: What is the Bermuda triangle?

This one will take a little longer to explain.

For decades, the Atlantic Ocean’s fabled Bermuda Triangle has captured the human imagination with unexplained disappearances of ships, planes, and people.

The Bermuda Triangle is an area roughly formed between Miami, Puerto Rico, and Bermuda. Some speculate that unknown and mysterious forces account for unexplained disappearances, like extraterrestrials capturing humans for study; others say this area has something to do with the lost continent of Atlantis; still others say there are vortices in this region that suck objects into other dimensions.  Some explanations are more grounded in science, if not in evidence.  These include oceanic flatulence (yes, there is such a thing … that’s when methane gas erupts from ocean sediments) and disruptions in geomagnetic lines of flux.

Well, it turns out that environmental considerations could explain many, if not most, of the disappearances.  The majority of Atlantic tropical storms and hurricanes pass through the Bermuda Triangle, and in the days prior to improved weather forecasting, these dangerous storms claimed many ships.  Also, the Gulf Stream can cause rapid, sometimes violent, changes in weather.  Added to this, the large number of islands in the Caribbean Sea creates many areas of shallow water that can be treacherous to ship navigation. And there is some evidence to suggest that the Bermuda Triangle is a place where a “magnetic” compass sometimes points towards “true” north, as opposed to “magnetic” north. 

The U.S. Navy and U.S. Coast Guard contend that there are no supernatural explanations for disasters at sea.  Their experience suggests that the combined forces of nature and human fallibility outdo even the most incredulous science fiction. They add that no official maps exist that delineate the boundaries of the Bermuda Triangle. The U. S. Board of Geographic Names does not recognize the Bermuda Triangle as an official name and does not maintain an official file on the area.

 Number Three: What’s the difference between an ocean and a sea?

Many people use the terms "ocean" and "sea" interchangeably when speaking about the ocean, but there is a difference between the two terms when speaking of geography (that’s the study of the Earth's surface).
Seas are smaller than oceans and are usually located where the land and ocean meet. And typically, seas are partially enclosed by land.  

Number two: How many oceans are there?

This one is kind of a trick question. There’s only one global ocean, but the ocean is usually geographically divided into the Atlantic, Pacific, Indian, Arctic, and Southern (or Antarctic) Oceans.

Of course, these five oceans are not separate bodies of water; they form one continuous oceanic mass.  The Pacific, the Atlantic and the Indian Oceans are known as the three major oceans.  The Southern Ocean is the 'newest' ocean. The boundaries of this ocean were set in 2000 by the International Hydrographic Organization, of which the U.S. is a member … our nation is represented by the National Ocean Service’s Office of Coast Survey.

Number one: How deep is the ocean?

The average depth of the ocean is about 4,267 meters (that’s 14,000 feet). The deepest part of the ocean is called the Challenger Deep and is located beneath the western Pacific Ocean in the southern end of the Mariana Trench, which runs several hundred kilometers southwest of the U.S. territorial island of Guam. Challenger Deep is about 11,030 meters (or 36,200 feet) deep. It’s named after the British survey ship Challenger II, which first surveyed the trench in 1951.

And it for this week. You can find many, many, many more Ocean Facts at You can browse through them by category, search for the fact topic you’re interested in, and subscribe to our Ocean Facts feed. And don’t forget to let us know if there’s an ocean-related question you’d like to have answered.

If you have any questions about this week’s podcast, about the National Ocean Service, or about our ocean, send us an email at  You can find us on the web at … and on Facebook and Twitter. Our handle is usoceangov.

And that’s all for this episode of Making Waves from NOAA’s National Ocean Service.  We will return in two weeks.