GEBCO 2019 bathymetry Challenger Deep and Sirena Deep

The Sirena Deep, originally named the HMRG Deep, was discovered in 1997 by a team of scientists from

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only ...

. Its directly measured depth of is third only to the

Challenger Deep The Challenger Deep is the deepest-known point of the seabed of Earth, with a depth of by direct measurement from deep-diving submersibles, remotely operated underwater vehicles and benthic landers, and (sometimes) slightly more by sonar ba ...

and Horizon Deep, currently the deepest known directly measured places in the ocean. It lies along the

Mariana Trench The Mariana Trench is an oceanic trench located in the western Pacific Ocean, about east of the Mariana Islands; it is the deepest oceanic trench on Earth. It is crescent-shaped and measures about in length and in width. The maximum kno ...

, 200 kilometers to the east of the Challenger Deep and 145 km south of

Guam Guam (; ch, Guåhan ) is an organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. It is the westernmost point and territory of the United States (reckoned from the geographic cen ...

Formation

The Sirena Deep was most probably formed, not through

transform fault A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subducti ...

motion as previously thought, but through a north-south

convergence Convergence may refer to: Arts and media Literature *''Convergence'' (book series), edited by Ruth Nanda Anshen * "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that united the four We ...

of the

Caroline plate The Caroline Plate is a minor tectonic plate that straddles the Equator in the eastern hemisphere located north of New Guinea. It forms a subduction zone along the border with the Bird's Head Plate and the Woodlark Plate to the south. A transform ...

and the

Pacific plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iz ...

, in which the Caroline plate is

subducting Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

. A group of scientists have hypothesized that the great depth of the Mariana Trench, the Challenger Deep, and the Sirena Deep is due to a tear in the subducting Caroline plate, causing deformation of the Pacific plate above. This tear would be located to the south of Guam, the same location of the deepest portion of the Mariana Trench. The tear would lead to unusual regional tectonics, another possible reason for the extreme depth. Scientists were alerted to the presence of the tear by the depth of strike-slip earthquakes, which were occurring too deep for them to be in the overriding plate. The Sirena Deep lies at the intersection of the East Santa Rosa Bank Fault and a trench axis south of Guam.

History

Discovery

In 1997, the Hawaii Mapping Research Group (HMRG) conducted a detailed

sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances ( ranging), communicate with or detect objects on ...

survey of the seafloor around Guam, discovering what is believed to be the second or third deepest location in the world's oceans; its existence was confirmed in 2001 and it was temporarily named HMRG Deep. In the same research mission, scientists found previously undiscovered faults,

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments ...

s, and

mud volcano A mud volcano or mud dome is a landform created by the eruption of mud or slurries, water and gases. Several geological processes may cause the formation of mud volcanoes. Mud volcanoes are not true igneous volcanoes as they do not produce lava ...

es. The data that confirmed the discovery were collected using the HAWAII MR1 mapping system. This mapping system has the ability to record both bathymetry and sidescan data at the same time. The two vessels that this system was used on were ''RIV Moana Wave'' in 1997 and ''RIV Melville'' in 2001.

Renaming

After a competition was held by Patricia Fryer, her doctoral student Sam Hulme, and Linda Tatreau to rename the HMRG Deep, the new name of Sirena Deep was chosen. Students from Guam and the

Northern Mariana Islands The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI; ch, Sankattan Siha Na Islas Mariånas; cal, Commonwealth Téél Falúw kka Efáng llól Marianas), is an unincorporated territory and commonwe ...

ages 18 and younger competed, with the winning name being suggested by Jermaine Sanders (aged 16) and John Meno (aged 14). The new name references the Guam folk-tale of Sirena, a young girl turned into half fish because of her disobedience. The new name will now appear on

geologic Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

and

bathymetric Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water ...

maps.

Crewed descent

Limiting Factor to be prepared for a dive into the Atlantic Ocean

On 7 May 2019

Victor Vescovo Victor Lance Vescovo (born 1966) is an American private equity investor, retired naval officer, space tourist and undersea explorer. He is a co-founder and managing partner of private equity company Insight Equity Holdings. Vescovo achieved th ...

(Pilot) and Alan Jamieson (Chief Scientist) made the first crewed descent to the bottom of the Sirena Deep in the Deep-Submergence Vehicle '' DSV Limiting Factor'' (a Triton 36000/2 model submersible) and measured a depth of ± by direct CTD pressure measurements. This descent occurred just after descending four times to the bottom of the nearby

. Work focused on geological, biological and video survey and collection in the Mariana Trench basin. They spent 176 minutes on the bottom of the Sirena Deep and the deepest piece of mantle rock ever recovered from the surface of the western slope of the Mariana Trench was collected. The Mariana Trench and the operating area was surveyed by the support ship, the Deep Submersible Support Vessel '' DSSV Pressure Drop'', with a Kongsberg SIMRAD EM124 multibeam echosounder system. The gathered data will be donated to the GEBCO Seabed 2030 initiative. The dive was part of th
Five Deeps Expedition
The objective of this expedition was to thoroughly map and visit the deepest points of all five of the world's oceans by the end of September 2019, which was achieved.

References

External links

former HMRG homepage
under the

University of Hawaii A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United Stat ...

HIGP homepage
(Hawaii Institute of

Geophysics Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' som ...

and Planetology), also under the University of Hawaii {{DEFAULTSORT:Hmrg Deep Geology of the Pacific Ocean Landforms of Oceania Lowest points of the World Ocean