Why There Are No Recorded Major Earthquakes in the Marianas Trench
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Why There Are No Recorded Major Earthquakes in the Marianas Trench

The largest subduction zone on Earth is the Marianas Trench that has never had an earthquake in recorded history going back to the 1600s. The reason for this turns out to be nothing more complicated then mud.

Since they first started recording earthquakes in the 1600s there have been no recorded major earthquakes from the Marianas Trench. This was one of the mysteries left behind by the epic voyage of the submersible the Trieste in January 23, 1953 by Welch and Picard. This was a mystery that wasn’t solved until decades later by deep sea drilling undertaken in the shallow northwest end of the Marianas Trench.

It should be understood that the Marianas Trench is the home of the largest subduction zone on earth, a place where the Pacific Plate is being consumed in the subduction zone. Unfortunately for the Pacific Ocean the rate of devouring is faster then the East Pacific Rise can produce new oceanic crust, hence the Pacific is doomed. The eventual consequence is that several million years in the future Australia will collide with the west coast of North America, but not until Los Angeles is consumed by the Aleutian Trench to the north.

When this collision of Australia and North America finally happens we will have the twin cities of Seattle and Sydney joined together. In any event this is going to take an estimated 100,000,000 years to occur or more. This can actually be calculated as long as the rate of consumption remains constant at three inches per year. By air it is 7,730 miles between the two cities.

During the late 1960s the Glomar Challenger was built for the specific reason of drilling cores from the seafloor in deep water. This was the vessel that during the 1970s undertook the job of drilling into the northwestern end of the Marianas Trench where the water was relatively shallow. It actually drilled into a hillock on the ocean’s floor that proved to be a mud volcano. What they found once they had penetrated the mud was a special type of rock called serpentinite. This rock is composed of altered seafloor, and is quite soft especially under the stresses found in a subduction zone where it quickly changes into mud.

This mud that is mainly composed of talc like that used in talcum powder acts as a lubricant between the rocks allowing the stresses caused by earth movements to be released without causing any earthquakes. In this case the Marianas Trench is just about unique because there are plenty of other trenches around the perimeter of the Pacific Ocean that are prone to gigantic earthquakes. Between the volcanoes and earthquakes the perimeter of the Pacific is called the Ring of Fire producing some of the largest of all recorded earthquakes.

As the largest of all oceanic trenches one would suspect that the Marianas Trench would also be the home to giant earthquakes, but because of something as simple as mud it has proved to be earthquake free - so far!

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Comments (1)

Interesting and educational topic.thanks John