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!
Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie
Modeling magma to find copper
13.01.2017 | Université de Genève
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction