The Bermuda Triangle covers approximately 500,000 square miles of the Atlantic Ocean.
The official dimensions (if you can call them that) claim the triangle is that area between Bermuda; San Juan, Puerto Rico; and Miami, Florida. However when you start plotting ocean disasters that are attributed to the Triangle its boundaries shift all over the North Atlantic and sometimes into the Eastern Pacific and Gulf of Mexico. See also: Mary Celeste and the Sargasso Sea
The Ocean Floor
The North-American Continental Shelf explains the wonderful blue water of the Caribbean. In many places throughout the Caribbean Islands when flying over the shelf it is possible to see large objects submerged several feet under the water. It's a splendid sight and it would make it seem that finding a lost plane submerged in these parts quite easy, especially in this day of Black Boxes (Flight Data Recorders, Cockpit Voice Recorders and Emergency Locator Transmitter).
While the Big Jets have all sorts of tracking gear, Small Aircraft only have the Emergency Locator Transmitter Unfortunately, the Black boxes don't work very well when they are submerged. Also, when the sandy bottom of the ocean floor is disturbed it can often cause the sand to lift up into a cloud and resettle on top of whatever disturbed it. To make matters worse, if a boat has capsized it may go completely unnoticed by all but the most sophisticated sonar equipment.
But these are only minor perils when it comes to searching for sunken craft in the Triangle. The real peril is that while many people have snorkeled in the wonderful shallow areas of the Caribbean, few have gone just a few miles away from these shallow areas where the continental shelf gives way to the ocean floor! Suddenly, within a matter of miles, what was once water only a couple hundred feet deep begins an ocean thousands of feet deep. About 100 miles north of Puerto Rico is the deepest part of the Atlantic Ocean: the Puerto Rico Trench, estimated at 30,100 ft (9200 meters) deep. The Florida Straits, between Miami and the Bahamas at around 5,000 or so feet deep. This is the shallow water where so many planes and boats have disappeared with out a trace. The 120 mile distance between the Grand Bahamas from New Providence lies the North East Providence Channel which has a depth of ranging between 6,000 and 12,000 feet (2,000-4,000 meters).
The Channel is at the tip of the basin which spreads out covering much of the ocean floor from Miami and the Bahamas out to Bermuda. This basin is approximately 18,000 feet (6,000 meters) deep.
Contrary to the Bermuda Triangle legend, the water of the islands is quite deep and turbulent.
This information is currently a rough estimate. However, the information is critical to understanding some of the reports of strange compass readings in the triangle. As more information is made available to me, I will update this information.
There are three north poles, Magnetic, Grid, and True or Celestial North.
True North -- True North is determined by Polaris, the North Star. It can be found using the Ursa Major (Big Dipper) and Ursa Minor (Little Dipper). To find it, line up the two stars at the end of the dipper and draw an imaginary line out to the last star in Ursa Minor. This is Polaris.
Grid North -- Grid North is the real North Pole, at 90 degrees latitude. It is the North Pole according to maps and globes. Because Polaris is not directly above Grid North, the two sometimes differ.
This is the answer to many of the strange compass readings that have been discussed when crossing the Atlantic. Columbus was one of the first Navigators to recognize that True North and Magnetic North were not the same thing, and he noted this in his log. He also surmised, correctly, 500 years ago, that the compass must point to something other than the North Pole.
There are only two longitudes in the world where Magnetic and Grid, or Magnetic, and True North align. These locations are near the center of Europe and near the eastern part of the United States.
At the tip of Portugal the difference between Magnetic and Grid North is about four degrees. As you travel west across the Atlantic, the difference between Magnetic and Grid North begins to increase. This difference can get as much as 22 degrees. This increase continues until you reach the middle of the Atlantic and the Sargasso Sea, and then slowly Grid and Magnetic begin to realign so that by the time you reach the southern tip of Florida the two are only one and a half degrees different. To get an idea of how Grid, True, and Magnetic Norths differ, go to any large library with a good map collection and ask to see the USGS 1:24,000 maps for your home town, a map for Washington State, New York State, and Kansas. On the bottom of the map will be a small diagram showing the differences between the three Norths.