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Joint
New Zealand - German 3D survey reveals massive seabed gas hydrate and
methane system
A
joint New Zealand-German research team has discovered a huge network
of frozen methane and methane gas in sediments and in the ocean near
New Zealand’s east coast.
A 3D image of one section of New Zealand's East Coast seafloor mapped in 3D, complete
with methane deposits and flares. [NIWA]
with methane deposits and flares. [NIWA]
11
May, 2014
The
16-strong team is using state-of-the-art 3D and 2D seismic and
echosounder technology to map both forms of methane within the ocean
and beneath the seafloor.
The area off the North Island’s east coast is known to have very large active landslides, up to 15km long and 100m thick, and the team set out to discover what is causing them to move.
What they discovered was direct evidence of widespread gas in the sediment and ocean, and indications of large areas of methane hydrate, ice-like frozen methane, below the seafloor. The team has identified 99 gas flares in a 50 km² area, venting from the seabed in columns up to 250 m high. This is believed to be the densest concentration of seafloor gas vents known in New Zealand. 3D seismic data show that landslides and faults allow the gas built up in the sediment to be released into the ocean.
The area off the North Island’s east coast is known to have very large active landslides, up to 15km long and 100m thick, and the team set out to discover what is causing them to move.
What they discovered was direct evidence of widespread gas in the sediment and ocean, and indications of large areas of methane hydrate, ice-like frozen methane, below the seafloor. The team has identified 99 gas flares in a 50 km² area, venting from the seabed in columns up to 250 m high. This is believed to be the densest concentration of seafloor gas vents known in New Zealand. 3D seismic data show that landslides and faults allow the gas built up in the sediment to be released into the ocean.
This
discovery reveals a hydrate and gas field very different from others
known in New Zealand.
“Previously all gas venting sites have been in deeper water and associated with large earthquake faults”, says NIWA marine geologist and voyage leader Dr Joshu Mountjoy.
“What we have found is high density methane flares in very shallow water, as well as gas building up beneath a large landslide and being released along the landslide margins”.
In a recently submitted scientific paper the team proposed that these landslides might be the seafloor equivalent of glaciers, but with frozen methane instead of water ice, or alternatively that pressurized gas is causing them to progressively move downslope. The results from this expedition indicate that both of these are possibilities and provide data to carefully test these hypotheses.
The expedition took the opportunity to deploy the German research institute GEOMAR’s high resolution 3D seismic equipment known as the P-Cable from NIWA’s research vessel Tangaroa
“This equipment is the best available for imaging fluid systems within the seafloor,” says co-leader Professor Sebastian Krastel of the University of Kiel. “The sediment, rocks and fluids we have mapped here are perfectly suited to this equipment, and the area mapped is one of the biggest ever mapped with the P-Cable seismic system.”
The work forms part of a larger project focused on understanding the dynamic interaction of gas hydrates and slow moving active landslides. Dubbed SCHLIP (Submarine Clathrate Hydrate Landslide Imaging Project), ongoing investigations in the project over the next decade will including drilling into the landslides themselves in 2016. This first part of the project, SCHLIP-3D, is a collaboration between NIWA, GNS Science and the University of Auckland from New Zealand, GEOMAR and the University of Kiel from Germany, Oregon State University from the USA, and the University of Malta.
“The initial findings are very important”, says Dr Mountjoy. “Methane is a very effective greenhouse gas and seabed methane release has the potential to dramatically alter the earth’s climate. As ocean temperatures change the methane hydrate system has the potential to become unstable.”
“In terms of natural hazards, the occurrence of very large slow landslides, rather than catastrophic ones, has major implications for the tsunami generating potential of landslides globally as slow landslides are unlikely to cause tsunami”.
“This type of slow moving submarine landslide is essentially unknown around the world, but it is very likely that they do occur widely and are an important process shaping continental margins”.
The team set off from Wellington on 14 April and finish the voyage there on 8 May. The work is funded from New Zealand by MBIE and Germany by DFG.
“Previously all gas venting sites have been in deeper water and associated with large earthquake faults”, says NIWA marine geologist and voyage leader Dr Joshu Mountjoy.
“What we have found is high density methane flares in very shallow water, as well as gas building up beneath a large landslide and being released along the landslide margins”.
In a recently submitted scientific paper the team proposed that these landslides might be the seafloor equivalent of glaciers, but with frozen methane instead of water ice, or alternatively that pressurized gas is causing them to progressively move downslope. The results from this expedition indicate that both of these are possibilities and provide data to carefully test these hypotheses.
The expedition took the opportunity to deploy the German research institute GEOMAR’s high resolution 3D seismic equipment known as the P-Cable from NIWA’s research vessel Tangaroa
“This equipment is the best available for imaging fluid systems within the seafloor,” says co-leader Professor Sebastian Krastel of the University of Kiel. “The sediment, rocks and fluids we have mapped here are perfectly suited to this equipment, and the area mapped is one of the biggest ever mapped with the P-Cable seismic system.”
The work forms part of a larger project focused on understanding the dynamic interaction of gas hydrates and slow moving active landslides. Dubbed SCHLIP (Submarine Clathrate Hydrate Landslide Imaging Project), ongoing investigations in the project over the next decade will including drilling into the landslides themselves in 2016. This first part of the project, SCHLIP-3D, is a collaboration between NIWA, GNS Science and the University of Auckland from New Zealand, GEOMAR and the University of Kiel from Germany, Oregon State University from the USA, and the University of Malta.
“The initial findings are very important”, says Dr Mountjoy. “Methane is a very effective greenhouse gas and seabed methane release has the potential to dramatically alter the earth’s climate. As ocean temperatures change the methane hydrate system has the potential to become unstable.”
“In terms of natural hazards, the occurrence of very large slow landslides, rather than catastrophic ones, has major implications for the tsunami generating potential of landslides globally as slow landslides are unlikely to cause tsunami”.
“This type of slow moving submarine landslide is essentially unknown around the world, but it is very likely that they do occur widely and are an important process shaping continental margins”.
The team set off from Wellington on 14 April and finish the voyage there on 8 May. The work is funded from New Zealand by MBIE and Germany by DFG.
Source
Joint
New Zealand - German 3D survey reveals massive seabed gas hydrate and
methane system
News Release, May 12, 2014, NIWA (National Institute of Water and Atmospheric Research), New Zealand
News Release, May 12, 2014, NIWA (National Institute of Water and Atmospheric Research), New Zealand
Related
Pockmarks
up to 11 km (6.8 mi) wide, off the coast of New Zealand's South
Island, in:
Sea of Okhotsk
Sea of Okhotsk
Submarine
volcano grows at record rate
A
volcano on the seafloor north of New Zealand has grown at a
record-breaking rate, says a new study
21
May, 2012
THE
MONOWAI CONE volcano,
1000km north of New Zealand, underwent an unprecedented period of
growth and collapse in mid-2011, providing new insight into the
behaviour of submarine volcanoes.
Over
a period of just five days, the volcano spewed out about 8.5 million
cubic metres of lava and debris. One portion of the summit grew by a
whopping 79m - equivalent to a 26-storey building - while another
collapsed by 19m.
The
changes were measured by scientists aboard the German research
vesselSonne,
with the study of the Monowai Cone aided by Dr Cornel de Ronde from
GNS Science in New Zealand.
The Monowai Cone
The
Kermadec Arc, between New Zealand and Tonga. (Credit: GNS Science)
"There
are very few documented examples of volcanoes growing this fast, and
they are all from on-land examples - this is the fastest known
growing volcano on the bottom of the sea," Cornel
told Australian
Geographic.
The
crew on the Sonne took
bathymetric (underwater topographic) measurements of the volcano at
two separate times during the survey, about three weeks apart, which
is something rare in the study of submarine volcanoes, Cornel says.
"Deep sea research is an expensive business, rarely can we go
back and re-survey a volcano within a few weeks or during the same
expedition."
The
Monowai Cone lies at the intersection of the Pacific and
Indo-Australian tectonic plates at the Tonga-Kermadec Arc - a
2500km-long chain of volcanoes stretching from New Zealand to Tonga.
According
to Dr Richard Arculus from The Australian National University, it is
among the most active arc volcanoes in the world.
The importance of submarine volcanoes
"Submarine
volcanism in island arcs...is a frontier area of study," Richard
says. He commended the researchers for making "accurate, repeat
measurements of volcano morphology over a limited period of time as
opposed to sporadic and widely spaced mapping efforts."
Studying
submarine volcanoes gives us insight into how the seafloor becomes
shaped by natural processes, but it can also offers clues for
mining mineral deposits on and.
Cornel
says that these kind of studies provide exploration companies "with
a better understanding of where to look for these mineral deposits in
uplifted terrains of ancient seafloor."
In
rare cases these submarine volcanoes could prove hazardous to
shipping, Cornel says: "Where the volcanoes are shallow - say
less than 400m in depth - they can erupt and expel enormous amounts
of gas into the water column, effectively preventing any vessel from
floating if they were situated immediately above the volcano."
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