Using a multibeam echo sounder, state-of-the-art equipment for mapping the ocean floor, scientists from the University of New Hampshire Center for Coastal and Ocean Mapping/Joint Hydrographic Center found four “bridges” spanning the trench and measured its deepest point with greater precision than ever before.
Research professor James Gardner and affiliate professor Andrew Armstrong, both of UNH’s Center for Coastal and Ocean Mapping/UNH-NOAA Joint Hydrographic Center (CCOM/JHC), presented their findings at the recent American Geophysical Union meeting in San Francisco, the world’s largest annual meeting of Earth and planetary scientists.
Mapping the entire Mariana Trench – approximately 400,000 square kilometers -- from August through October 2010, the researchers discovered four bridges spanning the trench and rising as high as 2,500 meters above its floor. While satellite images had suggested the trench might be spanned by one such ridge, Gardner says the mapping mission confirmed the existence of four such features. “That got me excited,” he says.
The ridges are being formed as the 180-million-year-old Pacific and far younger Philippine tectonic plates collide. Because the ocean’s crust cools as it ages, “the Pacific crust is much, much older, so it’s diving underneath the Philippine plate,” Gardner says. As seamounts on the Pacific plate are pulled beneath the Philippine plate, they are compacted against the wall of the trench, forming these ridges.
“It’s incredibly complex geology. These seamounts haven’t been completely subducted, they’re getting jammed up against the plate,” Gardner says. He surmises that the bridges are related to earthquake subduction zones, such as the one that caused the March 2011 earthquake in Japan.
The expedition also yielded the most precise measurement yet of Challenger Deep, the trench’s (and the Earth’s) deepest point, finding it to be 10,994 meters deep, plus or minus 40 meters. Calculated from thousands of depth soundings as well as detailed analysis of how the how the water column can alter the echo sounding signals, the new measurement is similar to other claims of the Challenger Deep’s depth, some of which are deeper.
“When you’re dealing with something that’s 11 kilometers deep, you have to deal with inherent uncertainties in the system,” says Gardner, noting that Challenger Deep is deeper than Mount Everest is high.
Multibeam echo sounders measure depth by sending sound energy to the ocean floor then analyzing the returning signal. Mounted beneath a ship, the instruments produce a fan-shaped swath of coverage of the seafloor. The resolution of the resulting images, at one pixel to every 100 meters, is far more precise than other earlier measurement systems. Hydrographers and ocean mappers such as Armstrong and Gardner describe the process of mapping an area as like “mowing the lawn,” making overlapping tracks over the area in question.
This mission to the Mariana Trench, the third and fourth cruises to that area by UNH scientists, was undertaken to gather data that can be used to support an extended continental shelf under Article 76 of the United Nations Convention of the Law of the Sea (UNCLOS). All data are publicly available on the CCOM website: www.ccom.unh.edu.
The University of New Hampshire, founded in 1866, is a world-class public research university with the feel of a New England liberal arts college. A land, sea, and space-grant university, UNH is the state's flagship public institution, enrolling 12,200 undergraduate and 2,300 graduate students.Images available to download:
Credit all images: University of New Hampshire Center for Coastal and Ocean Mapping/Joint Hydrographic Center
Beth Potier | EurekAlert!
A new dead zone in the Indian Ocean could impact future marine nutrient balance
06.12.2016 | Max-Planck-Institut für marine Mikrobiologie
NASA's AIM observes early noctilucent ice clouds over Antarctica
05.12.2016 | NASA/Goddard Space Flight Center
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Materials Sciences
06.12.2016 | Medical Engineering
06.12.2016 | Power and Electrical Engineering