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 ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

. Its directly measured depth of is third only to the

Challenger Deep The Challenger Deep is the List of submarine topographical features#List of oceanic trenches, deepest known point of the seabed of Earth, located in the western Pacific Ocean at the southern end of the Mariana Trench, in the ocean territory o ...

and

Horizon Deep The Tonga Trench is an oceanic trench located in the southwestern Pacific Ocean. It is the deepest trench in the Southern hemisphere and the second deepest on Earth after the Mariana Trench. The fastest plate-tectonic velocity on Earth is occurr ...

, 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 deep sea, deepest oceanic trench on Earth. It is crescent-shaped and measures about in length and in width. The maxi ...

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

Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...

Formation

The Sirena Deep was most probably formed, not through

transform fault A transform fault or transform boundary, is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either an ...

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), "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that ...

of the Caroline plate and the Pacific plate, in which the Caroline plate is

subducting Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second pla ...

. 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 o ...

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, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

s, and

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

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 in 2009 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), is an Territories of the United States, unincorporated territory and Commonwealth (U.S. insular area), commonwealth of the United States consistin ...

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 Oral literature, orature, or folk literature is a genre of literature that is spoken or sung in contrast to that which is written, though much oral literature has been transcribed. There is no standard definition, as anthropologists have used va ...

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 the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

and

bathymetric Bathymetry (; ) is the study of underwater depth of ocean floors ('' seabed topography''), river floors, or lake 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 February 10, 1966) is an American private equity investor, retired naval officer, sub-orbital spaceflight participant, and undersea explorer. He was a co-founder and managing partner of private equity company Insight ...

(Pilot) and Alan Jamieson (Chief Scientist) made the first crewed descent to the bottom of the Sirena Deep in the Deep-Submergence Vehicle ''

Limiting Factor A limiting factor is a variable of a system that causes a noticeable change in output or another measure of a type of system. The limiting factor is in a pyramid shape of organisms going up from the producers to consumers and so on. A factor not l ...

'' (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 educational institution, institution of tertiary education and research which awards academic degrees in several Discipline (academia), academic disciplines. ''University'' is derived from the Latin phrase , which roughly ...

HIGP homepage
(Hawaii Institute of

Geophysics Geophysics () is a subject of natural science concerned with the physical processes and Physical property, properties of Earth and its surrounding space environment, and the use of quantitative methods for their analysis. Geophysicists conduct i ...

and

Planetology Planetary science (or more rarely, planetology) is the scientific study of planets (including Earth), celestial bodies (such as moons, asteroids, comets) and planetary systems (in particular those of the Solar System) and the processes of their ...

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