Support the Arctic Sea Ice Forum and Blog

Author Topic: Antarctic Tectonics  (Read 49204 times)

AbruptSLR

  • ASIF Emperor
  • Posts: 16478
    • View Profile
  • Liked: 178
  • Likes Given: 12
Re: Antarctic Tectonics
« Reply #100 on: June 22, 2018, 09:53:20 AM »
I seem to recall that there are at least a couple sulphur volcanoes in WAIS, Now we have fast uplift as in the Barletta paper, and  drop in overburden pressure. That last may induce melt leading to bigger magma pool. But pressure is dropping, presumably decreasing the chance for violent eruptions. Which is good, since an eruption would probably drop albedo over a chunk of Antarctica enhancing surface melt.

sidd

There are many volcanoes beneath the WAIS, and at least see Replies: #4, #14, #72 & #83
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

solartim27

  • ASIF Middle Class
  • Posts: 528
    • View Profile
  • Liked: 13
  • Likes Given: 15
Re: Antarctic Tectonics
« Reply #101 on: July 02, 2018, 08:45:44 PM »
Very good article about volcanic heat flux under PIG from this tweet
The Antarctic Report (@AntarcticReport) Tweeted:
Helium isotopes (originating from Earth’s mantle) at front of Pine Island Glacier indicate substantial volcanic heat source upstream, contributing to subglacial melt - though rising temperatures in oceans are still biggest contributor to Antarctic melting https://t.co/dTETWoECvx https://t.co/bqhM5OhIj7 https://twitter.com/AntarcticReport/status/1013632346631749632?s=17

FNORD

litesong

  • ASIF Citizen
  • Posts: 374
    • View Profile
  • Liked: 20
  • Likes Given: 14
Re: Antarctic Tectonics
« Reply #102 on: July 04, 2018, 03:20:43 AM »
Helium isotopes (originating from Earth’s mantle) at front of Pine Island Glacier indicate substantial volcanic heat source upstream, contributing to subglacial melt - though rising temperatures in oceans are still biggest contributor to Antarctic melting.....
AGW deniers highlight continuously that volcanics are melting Ice Caps. Finally in this report, evidence shows that increasing ocean warmth increases affect Antarctic melting most. Also, whatever volcanic heats are  in Antarctica, AGW denier efforts must prove (& haven't) that present volcanic heats are greater than past volcanic heats of hundreds & thousands of years ago. 

solartim27

  • ASIF Middle Class
  • Posts: 528
    • View Profile
  • Liked: 13
  • Likes Given: 15
Re: Antarctic Tectonics
« Reply #103 on: July 04, 2018, 04:49:59 PM »
AGW deniers highlight continuously that volcanics are melting Ice Caps. Finally in this report, evidence shows that increasing ocean warmth increases affect Antarctic melting most.

The article also mentions a model showing no change in behavior at Thwaites due to addition of a mantle plume.
FNORD

gerontocrat

  • ASIF Governor
  • Posts: 3620
    • View Profile
  • Liked: 359
  • Likes Given: 7
Re: Antarctic Tectonics
« Reply #104 on: July 04, 2018, 05:26:53 PM »
Just a reminder of the additional volcanoes reported last year

https://www.theguardian.com/world/2017/aug/12/scientists-discover-91-volcanos-antarctica

Scientists discover 91 volcanoes below Antarctic ice sheet
This is in addition to 47 already known about and eruption would melt more ice in region affected by climate change

Quote
Scientists have uncovered the largest volcanic region on Earth – two kilometres below the surface of the vast ice sheet that covers west Antarctica.

The project, by Edinburgh University researchers, has revealed almost 100 volcanoes – with the highest as tall as the Eiger, which stands at almost 4,000 metres in Switzerland.

Geologists say this huge region is likely to dwarf that of east Africa’s volcanic ridge, currently rated the densest concentration of volcanoes in the world.

And the activity of this range could have worrying consequences, they have warned. “If one of these volcanoes were to erupt it could further destabilise west Antarctica’s ice sheets,” said glacier expert Robert Bingham, one of the paper’s authors. “Anything that causes the melting of ice – which an eruption certainly would – is likely to speed up the flow of ice into the sea.

“The big question is: how active are these volcanoes? That is something we need to determine as quickly as possible.”

The Edinburgh volcano survey, reported in the Geological Society’s special publications series, involved studying the underside of the west Antarctica ice sheet for hidden peaks of basalt rock similar to those produced by the region’s other volcanoes. Their tips actually lie above the ice and have been spotted by polar explorers over the past century.

But how many lie below the ice? This question was originally asked by the team’s youngest member, Max Van Wyk de Vries, an undergraduate at the university’s school of geosciences and a self-confessed volcano fanatic. He set up the project with the help of Bingham. Their study involved analysing measurements made by previous surveys, which involved the use of ice-penetrating radar, carried either by planes or land vehicles, to survey strips of the west Antarctic ice.

The results were then compared with satellite and database records and geological information from other aerial surveys. “Essentially, we were looking for evidence of volcanic cones sticking up into the ice,” Bingham said.

After the team had collated the results, it reported a staggering 91 previously unknown volcanoes, adding to the 47 others that had been discovered over the previous century of exploring the region.

These newly discovered volcanoes range in height from 100 to 3,850 metres. All are covered in ice, which sometimes lies in layers that are more than 4km thick in the region. These active peaks are concentrated in a region known as the west Antarctic rift system, which stretches 3,500km from Antarctica’s Ross ice shelf to the Antarctic peninsula.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

Rodius

  • ASIF Lurker
  • Posts: 17
    • View Profile
  • Liked: 8
  • Likes Given: 2
Re: Antarctic Tectonics
« Reply #105 on: July 05, 2018, 04:25:31 AM »
I am curious.... FYI - I am an amateur

Given the number of volcanoes found, what are the implications when ice melts, which reduces the weight on the land?
My thinking is the land will rise up due to less pressure being on it, the rising causes movement, movement on that scale is prone to cause earthquakes and, with the number of volcanoes, I can see an increase in volcanic activity.

Is this line of thinking possible?

RikW

  • ASIF Citizen
  • Posts: 124
    • View Profile
  • Liked: 14
  • Likes Given: 1
Re: Antarctic Tectonics
« Reply #106 on: July 05, 2018, 09:36:55 AM »
I'm wondering if this can trigger a chain reaction. We know mass balance has an influence on plate tectonics thus melting of the ice sheet can trigger earthquakes, but can it trigger an eruption? Because having enough mass-balance-change can trigger a vulcano, which eruption can in turn melt enough ice to trigger another eruption.

And if this can happen, does those kind of things happen on a scale of days, months, years, decades, millenia? I hope it will be millenia, but I fear it will be years/decades.

Daniel B.

  • ASIF Middle Class
  • Posts: 659
    • View Profile
  • Liked: 8
  • Likes Given: 29
Re: Antarctic Tectonics
« Reply #107 on: July 05, 2018, 03:36:53 PM »
Perhaps the best known instance of volcanoes and glaciers occurred in Katmai, Alaska. In 1912, a violent eruption collapse the cone and melting much of the surrounding glacier field.  Shortly afterwards, the glacier started to reform and expand.  It is rather spectacular.

kassy

  • ASIF Lurker
  • Posts: 75
    • View Profile
  • Liked: 9
  • Likes Given: 49
Re: Antarctic Tectonics
« Reply #108 on: July 05, 2018, 03:38:32 PM »
The extra uplift will cause extra volcanic activity but by how much is a known unknown. Those that are extinct won't do anything but i guess we don't know much about their history.

At least the known volcanoes are not that active:
https://en.wikipedia.org/wiki/List_of_volcanoes_in_Antarctica

I don't think a chain reaction like RikW describes is possible. Yes an eruption will melt some ice locally but that will be dwarfed by the ice loss on the continental scale.

RoxTheGeologist

  • ASIF Citizen
  • Posts: 313
    • View Profile
  • Liked: 39
  • Likes Given: 1
Re: Antarctic Tectonics
« Reply #109 on: July 05, 2018, 10:41:48 PM »

Pressure reduction moves the solidus (the temperature at which you get partial melt)  closer to the geotherm, resulting in more partial melt and magma formation. ... but this effect won't necessarily be observable for many lifetimes. You will get some faulting on isostatic rebound, but it's unlikely to increase heatflow to the surface dramatically

In addition, and this is what worries me, as pressure on magma chambers is lifted you will get more volcanic activity in the short term. I'm not sure if we could get into a feedback cycle of ice melt/pressure reduction/increased eruption/ice melt, but I'd guess it's a possibility with large regional magma chambers that are likely to exist below the rift zone, and it might happen very quickly in geological terms, maybe as short as a decade.


sidd

  • ASIF Governor
  • Posts: 3858
    • View Profile
  • Liked: 70
  • Likes Given: 0
Re: Antarctic Tectonics
« Reply #110 on: July 06, 2018, 05:38:36 AM »
" as pressure on magma chambers is lifted you will get more volcanic activity in the short term."

there is a paper on increased volcanic activity during deglaciations, but i have not the time to look it up. Perhaps some one will recall ?

sidd

AbruptSLR

  • ASIF Emperor
  • Posts: 16478
    • View Profile
  • Liked: 178
  • Likes Given: 12
Re: Antarctic Tectonics
« Reply #111 on: September 11, 2018, 11:19:25 PM »
The linked reference provides new insights into both magnetic anomalies and tectonic activity in Antarctica, including for the important West Antarctic Rift System (WARS):

A. V. Golynsky et al. (08 June 2018), "New Magnetic Anomaly Map of the Antarctic", Geophysical Research Letters, https://doi.org/10.1029/2018GL078153

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL078153

Abstract
The second generation Antarctic magnetic anomaly compilation for the region south of 60°S includes some 3.5 million line‐km of aeromagnetic and marine magnetic data that more than doubles the initial map's near‐surface database. For the new compilation, the magnetic data sets were corrected for the International Geomagnetic Reference Field, diurnal effects, and high‐frequency errors and leveled, gridded, and stitched together. The new magnetic data further constrain the crustal architecture and geological evolution of the Antarctic Peninsula and the West Antarctic Rift System in West Antarctica, as well as Dronning Maud Land, the Gamburtsev Subglacial Mountains, the Prince Charles Mountains, Princess Elizabeth Land, and Wilkes Land in East Antarctica and the circumjacent oceanic margins. Overall, the magnetic anomaly compilation helps unify disparate regional geologic and geophysical studies by providing new constraints on major tectonic and magmatic processes that affected the Antarctic from Precambrian to Cenozoic times.

Plain Language Summary
Given the ubiquitous polar cover of snow, ice, and seawater, the magnetic anomaly compilation offers important constraints on the global tectonic processes and crustal properties of the Antarctic. It also links widely separated areas of outcrop to help unify disparate geologic studies and provides insights on the lithospheric transition between Antarctica and adjacent oceans, as well as the geodynamic evolution of the Antarctic lithosphere in the assembly and breakup of the Gondwana, Rodinia, and Columbia supercontinents and key piercing points for reconstructing linkages between the protocontinents. The magnetic data together with ice‐probing radar and gravity information greatly facilitate understanding the evolution of fundamental large‐scale geological processes such as continental rifting, intraplate mountain building, subduction and terrane accretion processes, and intraplate basin formation.

Extract: "These new data provide key constraints into the extent of Cenozoic magmatism in the West Antarctic Rift System (WARS), which extends from the Ross Sea Embayment to the Amundsen (Gohl et al., 2013; Jordan et al., 2010) and possibly Bellingshausen Seas (Eagles et al., 2009). As in the Ross Sea sector (Behrendt, 1999), the Amundsen Sea Embayment was initially affected by distributed Cretaceous rifting related to New Zealand‐West Antarctica separation (Gohl et al., 2013) and subsequent Cenozoic narrow‐mode rifting (Jordan et al., 2010). The new aeromagnetic compilation reveals the occurrence of several narrow highly magmatic rift basins between the outcrops of Neogene volcanics in the Hudson Mountains (Figure 2), the Pine Island Glacier (Figure 2) catchment, and the Marie Byrd Land Dome (Young et al., 2017). Some of the proposed subglacial rift basins may also enhance glacial flow into the Amundsen Sea (Smith et al., 2013) and Bellingshausen Sea embayments (Bingham et al., 2012). Recent Curie depth estimates derived from magnetic data (Gohl et al., 2013) provide evidence for high geothermal heat flux offshore of the Thwaites Glacier (Figure 2; Dziadek et al., 2017) consistent with proposed Cenozoic tectono‐thermal reactivation in this WARS segment (Damiani et al., 2014). ADMAP‐2 facilitates extending these results inland into the catchment area of the climatically sensitive glacier and its neighbors."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 16478
    • View Profile
  • Liked: 178
  • Likes Given: 12
Re: Antarctic Tectonics
« Reply #112 on: October 26, 2018, 02:33:17 PM »
The second-generation Antarctic Digital Magnetic Anomaly Project is probing the structure of Antarctica's lithosphere:

A. V. Golynsky et al. (08 June 2018), "New Magnetic Anomaly Map of the Antarctic", Geophysical Research Letters, https://doi.org/10.1029/2018GL078153

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL078153

Abstract
The second generation Antarctic magnetic anomaly compilation for the region south of 60°S includes some 3.5 million line‐km of aeromagnetic and marine magnetic data that more than doubles the initial map's near‐surface database. For the new compilation, the magnetic data sets were corrected for the International Geomagnetic Reference Field, diurnal effects, and high‐frequency errors and leveled, gridded, and stitched together. The new magnetic data further constrain the crustal architecture and geological evolution of the Antarctic Peninsula and the West Antarctic Rift System in West Antarctica, as well as Dronning Maud Land, the Gamburtsev Subglacial Mountains, the Prince Charles Mountains, Princess Elizabeth Land, and Wilkes Land in East Antarctica and the circumjacent oceanic margins. Overall, the magnetic anomaly compilation helps unify disparate regional geologic and geophysical studies by providing new constraints on major tectonic and magmatic processes that affected the Antarctic from Precambrian to Cenozoic times.

Plain Language Summary
Given the ubiquitous polar cover of snow, ice, and seawater, the magnetic anomaly compilation offers important constraints on the global tectonic processes and crustal properties of the Antarctic. It also links widely separated areas of outcrop to help unify disparate geologic studies and provides insights on the lithospheric transition between Antarctica and adjacent oceans, as well as the geodynamic evolution of the Antarctic lithosphere in the assembly and breakup of the Gondwana, Rodinia, and Columbia supercontinents and key piercing points for reconstructing linkages between the protocontinents. The magnetic data together with ice‐probing radar and gravity information greatly facilitate understanding the evolution of fundamental large‐scale geological processes such as continental rifting, intraplate mountain building, subduction and terrane accretion processes, and intraplate basin formation.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 16478
    • View Profile
  • Liked: 178
  • Likes Given: 12
Re: Antarctic Tectonics
« Reply #113 on: November 07, 2018, 08:50:58 PM »
The linked reference includes discussion on how the GOCE satellite has helped to unveil the heterogeneity in Antarctica's lithosphere:

Jörg Ebbing et al. Earth tectonics as seen by GOCE – Enhanced satellite gravity gradient imaging, Scientific Reports (2018). DOI: 10.1038/s41598-018-34733-9

https://www.nature.com/articles/s41598-018-34733-9

Extract: "In remote frontiers like that Antarctic continent, where even basic knowledge of lithospheric feature remains incomplete, the curvature images help unveil the heterogeneity in lithospheric structure, e.g. between the composite East Antarctic Craton and the West Antarctic Rift System.

In the curvature products (and especially in the topographic and isostatic corrected shape index) interior East Antarctica appears to include at least three major heterogeneous lithospheric domains.  one correlates with the Mawson Craton, which included also large parts of southern Australia prior to Gondwana break-up, while the second corresponds to the region of the inferred Tonian Oceanic Arc Superterrane, in the interior of Dronning Maud Land.  These domains appear to be separated by the region of the Gamburtsev Subglacial Mountains, where the crust is up to 60 km thick, and an orogenic belt of inferred ca. 1 Ga or ca 550 ma age has been proposed.  The origin of the third domain, apparently lying between the Weddell Sea and South Pole, and its relations with the Mawson Craton remains unclear.  This poorly explored region includes the so-called Polar Gap south of 83oS, where GOCE data are not available (due to the inclination of the satellite orbit) and hence lower resolution GRACE data are used instead.  These three distinct domains are not apparent in currently available seismic tomography and represent an important new element to study Antarctica in relations to global plate tectonic reconstructions, both before and after the break-up of Gondwana."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson