Location of the Mariana Trench
The Pacific plate is subducted above the Mariana Plate, creating the Mariana trench, and (further on) the arc of the Mariana islands, as water trapped in the plate is released and explodes upward to form island volcanoes.
The
Mariana Trench
is the deepest known
submarine trench
. It is also the deepest known location on
Earth
itself.
[1]
It lies south and east of the
Mariana Islands
, and has a depth up to 10,971 m (7 miles). The western end of the trench is near
Guam
.
The trench is about 2,550 kilometres (1,580 miles) long but only an average of 69 kilometres (43 miles) wide.
The deepest part of the trench is known as the
Challenger Deep
. It is named after the British
Royal Navy
survey ship
HMS Challenger
, whose expedition of 1872?76 made the first recordings of its depth.
A 2009
sonar
mapping of the Challenger Deep from the
Kilo Moana
found a spot with a depth of 10,971 m (35,994 ft) (6.82 miles). The sonar system has an accuracy of better than 0.2% of water depth.
[2]
[3]
Water pressure is more than a thousand times as great as at the surface.
The Challenger Deep has been reached four times by submersibles, namely the manned
bathyscaphe
Trieste
on 23 January 1960, the unmanned robotic deep-sea probes
Kaiko
(Japanese) in 1995 and
Nereus
(U.S.) in 2009, and by
James Cameron
in the Deepsea Challenger on 26 March, 2012.
[4]
Cameron was able to film a
3D movie
of the bottom of the trench.
[5]
The HMS
Challenger
expedition found
radiolaria
in the two dredged samples taken when the Challenger Deep was first discovered.
[6]
[7]
On their 1960 descent, the crew of the
Trieste
noted that the floor consisted of
diatomaceous
ooze and reported observing "some type of
flatfish
, resembling a
sole
, about 1 foot long and 6 inches across" lying on the seabed.
[8]
The report has since been questioned, with suggestions that it may have been a
sea cucumber
. The video camera on board the
Kaiko
probe spotted a sea cucumber, a
scale worm
and a
shrimp
at the bottom.
[1]
[9]
At the bottom of the Challenger deep, the
Nereus
probe spotted one
polychaete
worm about an inch long.
[10]
An analysis of the sediment samples collected by
Kaiko
found large numbers of simple organisms at 10,900 m (35,800 ft).
[11]
The overwhelming majority of the organisms collected were simple, soft-shelled
foraminifera
(432 species according to National Geographic).
[12]
Eighty-five percent of the specimens were organic, soft-shelled forams. This is unusual compared to samples of
sediment
from other deep-sea environments, where the percentage of
organic-walled foraminifera
ranges from 5% to 20%. As small organisms with hard,
calcareous
shells
have trouble growing at extreme depths because of the high solubility of
calcium carbonate
in the pressurized water, scientists theorize that the preponderance of soft-shelled organisms in the Challenger Deep may have resulted from survivors of the
biosphere
present when the Challenger Deep was shallower than it is now.
The trench formed because of a large boundary
[13]
where two oceanic
tectonic plates
have converged (collided).
At the boundary, the western edge of the
Pacific Plate
is
subducted
beneath the small
Mariana Plate
. Because the Pacific plate is the largest of all the tectonic plates on Earth, crustal material at its western edge has had up to 170 million years to compact and become very dense; hence its great height-difference relative to the higher-riding Mariana Plate, at the point where the Pacific Plate crust is subducted. This deep area is the Mariana trench proper. The movement of these plates is also responsible for the formation of the Mariana Islands.
- ↑
1.0
1.1
"Mission to Marianas"
,
New Scientist
, 2 November 1996
- ↑
"Daily Reports for R/V KILO MOANA June and July 2009"
. University of Hawaii Marine Center. 2009-06-04. Archived from
the original
on 2012-05-24
. Retrieved
2009-06-04
.
- ↑
"Inventory of scientific equipment aboard the R/V KILO MOANA"
. University of Hawaii Marine Center. 2009-06-04. Archived from
the original
on 2012-12-14
. Retrieved
2009-06-04
.
- ↑
Child, Ben (26 March 2012).
"Mariana Trench: James Cameron completes record-breaking mission"
.
The Guardian
.
London
:
GMG
.
ISSN
0261-3077
.
OCLC
60623878
. Retrieved
27 March
2012
.
- ↑
YouTube
account of the Challenger Deep descent.
[1]
- ↑
[2]
, entry on March 23, 1875.
- ↑
[3]
, Report on the Radiolaria collected by H.M.S. Challengerby Ernst Haeckel.
- ↑
"To the bottom of the sea"
Archived
2008-12-03 at the
Wayback Machine
, T.A. Heppenheimer, AmericanHeritage.com
- ↑
"The last frontier"
Archived
2010-11-03 at the
Wayback Machine
,
Time
, August 14, 1995
- ↑
Accessed Oct. 8, 2009
Archived
1996-10-27 at the
Wayback Machine
Geography of the ocean floor near Guam with some notes on exploration of the Challenger Deep.
- ↑
Todo, Yuko (2005). "Simple Foraminifera flourish at the ocean's deepest point".
Science
.
307
(5710): 689.
doi
:
10.1126/science.1105407
.
PMID
15692042
.
S2CID
20003334
.
- ↑
Roach, John (February 3, 2005).
"Life is found thriving at Ocean's deepest point"
.
National Geographic News
.
- ↑
called the Izu-Bozin-Mariana Arc (IBM)