The Mariana Trench. Image: Wikimedia
We all know the Mariana Trench is the deepest spot in all the oceans of the Earth. It was discovered in 1875 by the H.M.S. Challenger using sounding equipment. In 1951 it was sounded again by the H.M.S. Challenger II and the deepest part of the ocean was named Challenger Deep. The trench is just over 36,200 feet deep.
It’s difficult to put that into perspective. If you had a building with 3,620 stories (each story 10 feet tall) it would represent the depth of the trench. The tallest building in the world (in Dubai) measures 2,717 feet and has 160 floors. It would take over 13 of those buildings in Dubai stacked on top of one another just to reach the depth of the Mariana Trench. Mount Everest is only 29,000+ feet tall (but is growing all the time, I’ll explain that another time). The Trench is 1,580 miles long, or almost the distance from New York City to Denver, Colorado. To get an idea of how deep the Trench is please check out this graphic:
It’s difficult to put that into perspective. If you had a building with 3,620 stories (each story 10 feet tall) it would represent the depth of the trench. The tallest building in the world (in Dubai) measures 2,717 feet and has 160 floors. It would take over 13 of those buildings in Dubai stacked on top of one another just to reach the depth of the Mariana Trench. Mount Everest is only 29,000+ feet tall (but is growing all the time, I’ll explain that another time). The Trench is 1,580 miles long, or almost the distance from New York City to Denver, Colorado. To get an idea of how deep the Trench is please check out this graphic:
Trench Comparison. The depth of the Trench is 36,070 feet in this image but my research shows over 36,200. Image: Florida News Journal
How did the Trench form? The Trench is actually the product of plate tectonics. The theory of plate tectonics is as follows: The Earth’s crust is divided into plates that float around on top of molten rock in the lithosphere. These plates collide and separate all over the place. Here’s a diagram of the plates on the Earth:
Plates of the Earth. Image: Wikimedia
The Pacific Plate is pushing into the Philippine Plate in the western Pacific Ocean. Oceanic plates are usually made of the rock type basalt. In many cases it is an oceanic plate sliding under (or subducting) beneath a continental plate (made of granite).
In the case of the Trench it is two oceanic plates colliding. Due to the fact that the Philippine Plate is older and more dense it stays on top as the Pacific Plate slides underneath it. A dip in the crust forms where the one plate dives under the other. This dip, which is just a slight dent in terms of the Earth as a whole, is the Mariana Trench. See this graphic for a better idea of what I’m talking about:
In the case of the Trench it is two oceanic plates colliding. Due to the fact that the Philippine Plate is older and more dense it stays on top as the Pacific Plate slides underneath it. A dip in the crust forms where the one plate dives under the other. This dip, which is just a slight dent in terms of the Earth as a whole, is the Mariana Trench. See this graphic for a better idea of what I’m talking about:
The Mariana Trench is formed by the Pacific Plate subducting under the Philippine Plate. Click image for source.
As the Pacific Plate subducts father into the Earth it begins to melt. This molten rock is less dense and rises to the surface creating islands and volcanoes in the Philippine Plate. You can see that area of islands and volcanoes in the diagram above. It is labeled as the Mariana Islands. The volcanoes on the northwest coast of the United States are created in this same fashion. In fact, the volcanoes around the entire Pacific Rim are created by this process.
Anyway, back to the Trench. The pressure at the bottom is immense. If you were at the bottom the pressure you'd feel would be created by the weight of the ocean on top of you. Ever feel pressure changes in the deep end of the pool when you dive to the bottom? It’s caused by the pool water pushing down on you. Well there is 15,750 psi at the bottom of the Trench. That’s 15,750 POUNDS of force on every inch of your body. This is over 1,000 times the atmospheric pressure at sea level. Even water is denser because it’s compacted due to the weight above it. The water temperature is just above freezing. Basically, it’s not a place you want to visit.
Life in the Trench goes on as it does on the surface of the Earth. Many different aquatic life forms live down there. Thermal vents heat the surrounding water to over 500 degrees while water away from the vents is near freezing. The vents also disperse minerals into the water to make it suitable for life. Many critters feed on carcasses of animals that sink from the top of the ocean down into the trench.
So you would think that, because the trench is so deep, that Challenger Deep is the closest spot to the center of the Earth, right? Nope! There are actually spots that are closer to the center of the Earth.
How is this possible?
Because the Earth is spinning. Think about a water balloon. If you were to hang the balloon from a string and spin it like a basketball it would bulge in the center. The top and bottom of the balloon would move closer to the core of the balloon. This same concept applies on a much larger scale with the Earth. The diameter of the Earth when measured on the equator is 7,926.38 miles. The diameter of the Earth when measured at the poles is 7,899.84 miles. That’s a difference of 26.54 miles.
Because the Mariana Trench is near the equator it is greatly affected by this equatorial bulge; thus, the trench is not the closest place to the center of the Earth. If you head into the arctic there are some places on the seabed that are much closer than the Trench is to the core. So just remember, you can save yourself 26 miles of travel if you want to go to the core through the poles.
I hope you found this post interesting and informative. If you have any questions feel free to ask on my facebook page.
Information sources:
Mariana Trench by LiveScience
Mariana Trench by Oregon State
An awesome Earth Science teacher by the name of Ann Aleo at Courtland High School in Spotsylvania, Virginia.
Anyway, back to the Trench. The pressure at the bottom is immense. If you were at the bottom the pressure you'd feel would be created by the weight of the ocean on top of you. Ever feel pressure changes in the deep end of the pool when you dive to the bottom? It’s caused by the pool water pushing down on you. Well there is 15,750 psi at the bottom of the Trench. That’s 15,750 POUNDS of force on every inch of your body. This is over 1,000 times the atmospheric pressure at sea level. Even water is denser because it’s compacted due to the weight above it. The water temperature is just above freezing. Basically, it’s not a place you want to visit.
Life in the Trench goes on as it does on the surface of the Earth. Many different aquatic life forms live down there. Thermal vents heat the surrounding water to over 500 degrees while water away from the vents is near freezing. The vents also disperse minerals into the water to make it suitable for life. Many critters feed on carcasses of animals that sink from the top of the ocean down into the trench.
So you would think that, because the trench is so deep, that Challenger Deep is the closest spot to the center of the Earth, right? Nope! There are actually spots that are closer to the center of the Earth.
How is this possible?
Because the Earth is spinning. Think about a water balloon. If you were to hang the balloon from a string and spin it like a basketball it would bulge in the center. The top and bottom of the balloon would move closer to the core of the balloon. This same concept applies on a much larger scale with the Earth. The diameter of the Earth when measured on the equator is 7,926.38 miles. The diameter of the Earth when measured at the poles is 7,899.84 miles. That’s a difference of 26.54 miles.
Because the Mariana Trench is near the equator it is greatly affected by this equatorial bulge; thus, the trench is not the closest place to the center of the Earth. If you head into the arctic there are some places on the seabed that are much closer than the Trench is to the core. So just remember, you can save yourself 26 miles of travel if you want to go to the core through the poles.
I hope you found this post interesting and informative. If you have any questions feel free to ask on my facebook page.
Information sources:
Mariana Trench by LiveScience
Mariana Trench by Oregon State
An awesome Earth Science teacher by the name of Ann Aleo at Courtland High School in Spotsylvania, Virginia.
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