- 4394
- FIRE -
under the ocean? - A sleeping
subduction zone could awaken and form a new 'Ring of Fire' that swallows the
Atlantic Ocean. This slumbering
subduction zone below the Gibraltar Strait is active and could break into the
Atlantic Ocean in 20 million years' time, giving birth to an Atlantic
"Ring of Fire."
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-------------------------- 4394 -
FIRE -
under the ocean?
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- This subduction zone is creeping westward
and could one day "invade" the Atlantic Ocean, causing the ocean to
slowly close up. The subduction zone,
also known as the “Gibraltar arc” or trench, currently sits in a narrow ocean
corridor between Portugal and Morocco.
-
- Its westward migration began around 30
million years ago, when a subduction zone formed along the northern coast of
what is now the Mediterranean Sea, but it has stalled in the last 5 million years, prompting some
scientists to question whether the Gibraltar arc is still active today.
-
- It appears that the arc is merely in a
period of quiet. This lull will likely
last for another 20 million years, after which the Gibraltar arc could resume
its advance and break into the Atlantic in a process known as "subduction
invasion."
-
- The Atlantic Ocean hosts two subduction
zones that researchers know of, the
“Lesser Antilles” subduction zone in the Caribbean and the “Scotia arc”, near
Antarctica. These subduction zones
invaded the Atlantic several million years ago. We are approaching the tipping point.
-
- Modeling of this kind requires advanced
tools and computers that weren't available even a few years ago. We can now simulate the formation of the
Gibraltar arc with great detail and also how it may evolve in the deep future.
-
- If the Gibraltar arc invades the Atlantic
Ocean, it could contribute to forming an Atlantic subduction system analogous
to a chain of subduction zones that circles the Pacific Ocean, called the “Ring
of Fire”. A similar chain forming in the Atlantic would lead to oceanic crust
being recycled into the mantle via subduction on both sides of the Atlantic,
gradually swallowing and closing up this ocean.
-
- The Gibraltar arc's grinding advance over
the last 5 million years could explain the relative lack of seismicity and
volcanism in the region. The subduction zone's tectonic silence is a direct
result of its extended period of stalled movement.
-
- If the movement along the subduction
interface were small, the accumulation of the seismic strain would be slow and
may take hundreds of years to accumulate.
This agrees with the long recurrence period estimated for big
earthquakes in the region.
-
- Although many smaller earthquakes have been
recorded since, the last major earthquake to rock the region was the “1755
Great Lisbon Earthquake”, which reached an estimated 8.5 to 9.0 on the moment
magnitude scale.
-
- What are the deepest spots in Earth's
oceans? Could there be a volcano down
there?
What types of sea creatures
live at these depths? There are deep
realms on our planet that seem almost extraterrestrial. Translucent fish flit
back and forth while strange, flower-like crinoids sway in the water. But of
all the submarine canyons and trenches out there, what are the deepest, darkest
spots in each of the world's five oceans?
-
- The deepest place in the Pacific Ocean (and
on Earth) is the Mariana Trench. The trench's deepest point is the Challenger
Deep near the U.S. territory of Guam.
This is a plunge that's almost 36,000 feet below the water's surface.
-
- The deepest region in the Atlantic Ocean is
the Milwaukee Deep in the 27,585-foot-deep axis of the Puerto Rico Trench.
Coming in at 23,917 feet deep is a nameless region at the bottom of the Indian
Ocean.
-
- The Southern Ocean (also known as the
Antarctic Ocean) goes all the way down to 24,229 feet in the South Sandwich
Trench, and the Arctic Ocean goes down to 16,000 feet deep at Molloy Deep in
the Fram Strait.
-
- Such areas are far from the reach of the
sun and may appear to be nothing but gaping mouths of impenetrable darkness.
But what do scientists know about these final frontiers? Why are there so many giants in the deep sea?
-
- The Mariana Trench is a 1,580-mile-long
oceanic abyss where several of the planet's deepest points can be found. Only 27 people have ever been to the
Challenger Deep, the Mariana Trench's deepest point: The first to go there were
explorer Jacques Piccard and Navy Lt. Don Walsh, who ventured there in 1960.
-
- Mackenzie Gerringer went on an expedition in
2014 to the 34,448-foot-deep Sirena Deep (one of the other deepest parts of the
trench) with colleagues from the University of Hawaii at Mānoa. There's no sunlight. Temperatures are cold, typically about 1-2°C
[33.8 to 35.6 degrees Fahrenheit]. Pressures are high, up to 15,000 pounds per
square inch at the ocean's greatest depths.
-
- Despite the extreme conditions, life exists
in the deepest parts of our planet's seas.
The types of creatures that thrive at extreme depths tend to be similar,
even though different species might be unique to different regions. Certain creatures appear at specific
depths. The bottom of a species' depth
range is controlled by adaptations to pressure, and the top of its range may be
controlled by predation or competition.
-
- During Gerringer's expedition they
discovered a new species of Mariana snailfish. The newfound critter was a hadal
snailfish, named for the hadal zone, the part of the ocean that is between
about 19,700 feet and 36,000 feet deep and only occurs in marine trenches.
-
- Critters like this are specially adapted to
survive in the deep extreme pressures that push against the body and impair
enzymes and proteins. Mariana snailfish and other hadal species are equipped to
handle this with enzymes that operate more effectively under extremely high
pressure. They also produce a molecule known as TMAO (trimethylamine N-oxide)
to keep the pressure from messing with the proteins in their bodies.
-
- In the Mariana Trench,16,000 feet down, cusk eels and rattail fish swam among
decapod shrimp. As probe cameras dove deeper, these species gave way to
snailfish and giant amphipods, and deeper still, different species of mostly
smaller amphipods and shrimp appeared. The deepest at which any fish were seen
was 26,250 feet.
-
- Off the coast of Puerto Rico and south of
the tip of Florida, the Puerto Rico Trench is evidence of an ancient subduction
event. Most of these hadal habitats are
trenches that form via subduction, where one tectonic plate slides under
another, creating a deep valley.
-
- Shifting tectonic plates also explain the
presence of a group of volcanic islands scattered nearby, as subduction is the
same kind of tectonic activity that can cause magma to rise up from beneath
Earth's crust.
-
- Those are not the only volcanoes around
this trench. Deep underwater, a volcano that erupted in mud was found close to
the 26,000-foot-depth mark. Areas
around this trench are prone to earthquakes and tsunamis because of subduction.
There is even a fault in the Puerto Rico Trench that looks eerily like a
submerged version of the San Andreas Fault.
-
- The deepest part of the trench is the
Milwaukee Deep, which explorer Victor Vescovo dived to in a crewed submersible
in 2018 (Vescovo had previously gone down to the Mariana Trench and was the
first person to ever dive to the Challenger Deep twice).
-
- The deepest parts of the Indian Ocean's
Java Trench and the Antarctic Ocean's South Sandwich Trench were both
determined by the Five Deeps Expedition (FDE) in 2021. These unnamed regions had been mostly
unexplored. The South Sandwich Trench,
the only hadal zone on Earth that experiences sub-zero temperatures, had not
been explored at all before this mission.
-
- The expedition's researchers explored the
hidden depths of the ocean by sending down remotely operated vehicles (ROVs).
The team used a Deep Submergence Vehicle (DSV) and three additional landers,
robots carrying multiple instruments, such as sensors, that fall to the bottom
and probe the seafloor.
-
- In the Java Trench, cameras on the FDE
landers observed hadal snailfish, sea cucumbers and weird-looking lifeforms,
such as a sea squirt that floated in the dark waters like a ghostly balloon. Topical Studies in Oceanography highlighted
the fauna in the South Sandwich Trench. In these freezing waters, researchers
found snailfish amphipods, brittle stars, sea cucumbers, sponges and crinoids.
-
- Going from the Antarctic to the Arctic
Ocean, the Five Deeps Expedition next investigated the “Molloy Deep” in the
Fram Strait, between the east of Greenland and the Svalbard islands off the
northern coast of Norway. No other mission had ever seen the bottom of the
Molloy Deebefore.
-
- In the Fram Strait, fluctuations in levels
of fresh and salt water impact populations of phytoplankton and other microbes.
Climate change has impacted the Arctic Ocean the most out of any of the world's
five oceans, and the thickness of sea ice has been steadily decreasing since
1990.
-
- Few creatures live in the Molloy Deep. It
is essentially an enormous crater, and organic matter gathers and falls down
the sides, but there are not many creatures that inhabit this barren region,
scientists at the Maier-Kaiser Lab (which is part of the Woods Hole
Oceanographic Institution in Massachusetts) found when they searched it for
larvae. The only animal that has been caught on camera there is a type of
deep-sea sea cucumber known as a sea pig.
-
- The deep sea is closely connected to the
surface oceans. Human activities such as
plastic pollution and climate change are already influencing deep-sea habitats
and it's important that we understand, appreciate, and protect these
ecosystems.
-
-
March 18, 2023 FIRE
- under the ocean? 4394
------------------------------------------------------------------------------------------
-------- Comments appreciated and Pass it on to
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--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
copies or Index of all reviews
--- to:
------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Wednesday, March 20,
2024
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