The last time I wrote an article for Volcanocafe it was a guest post about the Galapagos Islands, but now I’m a new member of the Volcanocafe writing team (a little bit more about me later).
Deep in the South Atlantic Ocean lies an archipelago of uninhabited volcanic islands, the South Sandwich Islands. A British overseas territory located within the sub-Antarctic region. The South Sandwich Islands consists of 11 islands, they are Zavodovski, Visokoi, Leskov, Candlemas, Vindication, Saunders, Montagu, Bristol, Bellingshausen, Cook, and Thule all formed as a result of the subduction of a part of the South American Plate underneath the Scotia Plate as well as numerous seamounts. Because of the remote location of the islands and the volatile nature of the seas and climate, human expeditions are very rare so we have to almost always rely on satellite imagery for observations subject to weather.
The age of the subducting oceanic crust ranges from 27 million years old in the south to 80 million years old to the north. The East Scotia Ridge spreading centre cuts through the Scotia Plate from the northern part of the island arc, to the south forming the minor tectonic plate, the South Sandwich Plate. The Protector Seamounts forms the northenmost Volcanic centre of the island arc with the Scoresby Seamount being the northernmost volcano of the arc. Nelson Seamount is the southernmost volcano of the island arc, located to the south of the Kemp and Adventure Calderas. The Kemp and Adventure Calderas are other undersea volcanoes which are located to the southwest of the Southern Thule Islands. The volcanoes of the South Sandwich arc are predominately of Basaltic or Basaltic-Andesitic composition with minor amounts of Andesite, Dacite, or Rhyolite.
Out of the historical eruptions ever recorded in the South Sandwich Islands since 1819 there may have been many more than we think, just that these islands are very rarely visited given their remote location and hostile environment. But now, thanks to modern satellite technology we’re able to monitor the volcanic activity more often today. Historical eruptions in the South Sandwich Islands have occurred at the Protector Shoal Seamount, Mount Curry on Zavodovski Island, Lucifer Hill on Candlemas Island, Mount Michael and the northern flank on Saunders Island, Mount Belinda on Montagu Island, Mount Sourabaya and the west flank on Bristol Island, and the south flank of Bellingshausen Island. Other forms of volcanic activity observed includes fumaroles on Zavodovski Island, Leskov Island, Visokoi Island, Candlemas Island, and Bellingshausen Island, and also geysers and hot pools on Candlemas Island, and undersea hydrothermal venting on the Kemp and Adventure Calderas as well as the summits of the E2 and E9 segments in the East Scotia Ridge spreading centre.
The South Sandwich Islands are also home to a large colony of penguins especially of the Chinstrap and Adelie species. Species of seals and whales, as well as skuas are also present around the islands.
PROTECTOR SEAMOUNTS GROUP
The Protector seamounts make up the northernmost volcanic centre of the South Sandwich arc. They consist of Protector Shoal, Nimrod Bank, Endurance, Bisco, Tula, JCR, Quest caldera, and Scoresby. Because they all lie beneath the surface of the sea, not a lot is known about them. However, temperature readings from submersible dives on Scoresby and Quest caldera suggest that hydrothermal activity is occurring on these vents. Protector Shoal, a rhyolite volcano which is located on the south end of Nimrod Bank at -55m had it’s only historical eruption in 1962 when a large amount of pumice was ejected forming a pumice raft which drifted towards New Zealand.
Zavodovski is the northernmost island of the South Sandwich chain and is made up out of Basalt. The 551m high Mount Curry stratovolcano occupies the western side of the island while a lava platform makes up the eastern side of the island and to a lesser extent, the southern end of the island. Olivine-basalt is present on the east cliffs. Persistent fumarolic activity occurs at the summit and the crater of Mount Curry and is said to have been active since first sighted by explorer Fabian Gottlieb von Bellingshausen in 1819. An eruption was observed by Bellingshausen in 1819 and although no confirmed eruptions had been reported until 2016, it is likely that many eruptions may have occurred since it’s discovery. A possible sighting of a lava flow was observed in 1830. During 30th March 2016, a fishing vessel sighted an eruption which produced an ash plume that drifted east.
Leskov Island is a small cresent shaped island located west of Visokoi Island and southwest of Zavodovski Island. Made up entirely of Two-pyroxene andesite the island has a diameter of 900m long and 400m wide. A remnant of an eroded volcano, Crater Bay to the northeast side of the island is the main eruptive centre. No historical eruptions have been known on Leskov Island although fumarolic activity along the summit ridge was observed in 1911 and 1964.
Visokoi Island consists of a single stratovolcano, Mount Hodson and is predominately made up out of Basalt with lesser amounts of Basaltic-andesite. Much of the island is covered in permanent ice although the coastal areas can be ice free during summer. Basaltic-andesites were found at Irving Point on the east coast of the island. Scoria cones dot the lower flanks of Mount Hodson. Vapour has been observed on odd occasions in the past coming from the summit but nothing more could be confirmed. A fumarole on the north coast was reported in 1930. Although there had been no historical eruptions confirmed it is possible that some eruptive activity may have occurred up to almost the present day.
Candlemas Island has a distinction between the southern part of the island, and the northern peninsula. The southern part of the island is older than the northern peninsula and it consists of an ice covered volcanic edifice with two peaks on the east side, Mount Andromeda and Mount Perseus. The volcanic edifice of the southern part of the island is made up out of porphyritic basalt although some dacitic obsidian fragments were found on the northern cliffs. The edifice is eroded to the east but lavas dipping towards the west suggest that a former summit vent once occupied the area beyond the eastern coast. The northern peninsula of the island is younger but is more low lying and is made up out of andesite and dacite, it consists of lava fields and a younger volcano, Lucifer Hill. It is likely to have started out as a seperate island before eventually merging with the south. Gorgon Pool and Medusa Pool occupy the area which connects the northern peninsula with the southern part of the island. Eruptions on Lucifer Hill occurred in 1823 and in 1911. A lot of the lava fields around Lucifer Hill is said to have formed during recent times. In 1953-54 a glowing lava field was observed and in 1964 steam was reported to have been issuing from the youngest lava flow. Geysers and hot pools were observed on occasions during the 20th century. The Lucifer Hill Volcano currently displays persistent fumarolic activity while no eruptive nor fumarolic activity has ever been observed on the southern part of the island.
Vindication Island is located very close west-southwest of Candlemas Island and the two islands are seperated by a shallow shelf. Vindication is smaller than Candlemas Island but has been largely reduced by erosion and is bounded by high cliffs. The island is made up of porphyritic basalt with lesser amounts of basaltic-andesite and smaller amounts of palagonite-tuff on on the north coast. Quadrant Peak on the western side of the island may have been part of a once principal eruptive centre of the island. No volcanic activity of any form has been observed on Vindication Island.
Saunders Island is made up out of basalt and it lies midway within the South Sandwich island arc. While the 991m high glacier covered Mount Michael Volcano dominates the island, the north coast consists of Blackstone Plain, a low lying lava platform and the south east consists of a small cluster of parasitic cones, Ashen Hills. Cordelia Bay is located to the northeast. Two seamount chains are present to the northwest and southwest of the Saunders Island platform. Vitric palagonite-tuff is present at Nattriss Point while basaltic-andesite is present at Yellowstone Crags and olivine-basalt is present on Blackstone Plain. A 500m wide crater is present on the summit of Mount Michael with a smaller older crater to the southeast. The first observed eruption came in 1819 and a lava flow on the north flank was said to have occurred during the end of the 19th century. Eruptions on Mount Michael have been occurring on a regular basis since 1995. Vapour emissions have been repeatedly reported. Satellite data suggests that the occasional lava lake activity has occurred.
Montagu Island is the largest island in the archipelago and has a more broad shaped profile, it is almost entirely covered by ice. The Mount Belinda central cone is also the highest point on the island at 1370m. At least three small parasitic cones lie at the edge of the high plateau. A secondary volcano, Mount Oceanite lies at the southeast edge of the island. The island is almost entirely made up out of basalt though palagonite-tuff is present in the cliffs behind Horsburgh Beach on the west-southwest of the island. No eruptive nor fumarolic activity has been observed on the island until 2001 when Mount Belinda erupted. The eruption of Mount Belinda lasted until 2007, when a lava flow reached the north coast of the island within that time. Unconfirmed eruptions may have been detected between 1995 and 1998.
Glacier covered Bristol Island is located near the Southern Thule Islands group, near the southern end of the island arc. This largely porphyritic basaltic island consists of prominent peaks, Mount Sourabaya, Mount Darnley, and Havfruen Peak. A ridge runs from the inland east, down to the north coast of the island. Freezland Rock, Wilson Rock, and Grindle Rock which lie off the western tip of the island (Turmoil Point) may be remnants of a former volcano. Andesite and palgonite-tuff is present on Freezland Rock. Historical eruptions have occurred in 1823, 1935, 1936, 1950, 1956, and 2016. While most of the eruptions occurred from the summit vents (more likely Mount Sourabaya), the 1956 eruption occurred on the west side of the island close to Turmoil Point. The most recent eruption on Bristol Island occurred on Mount Sourabaya during April-August 2016 when satellite imagery picked up on thermal anomalies, eruption plumes, and two branches of lava flows which advanced to the west and to the north-northwest of Mount Sourabaya.
Bellingshausen Island is the smallest island of the Southern Thule Islands group at the south end of the island arc. It is made up almost entirely out of basaltic-andesite though palagonite-tuff is present on the northern summit crater wall. Lava fields are present on the south side of the island, and the underwater Resolution Caldera lies to the south of the island. Active fumaroles have been observed on the southern crater rim and an eruption occurred on the south side of the island sometime during the late 20th century.
Cook Island is the central island of the Southern Thule Islands group and the highest point on the island is Mount Harmer. Olivine basalt as well as andesite and dacite is present. No volcanic activity of any form has ever been observed on Cook Island.
Thule Island is the westernmost island of the Southern Thule Islands group and consists of a single stratovolcano, Mount Larsen. An ice filled caldera occupies the summit area while a lava flow emitted from a parasitic vent forms the low lying southeast tip of the island (Hewison Point). The island is eroded along the east coast and a possible underwater caldera occupies the area in Douglas Straight between the east of the island and Cook Island. Andesite and dacite, as well as olivine-basalt is present on the island while palagonite-tuff was found at the parasitic centre near Hewison Point. Steam was observed from the summit crater in 1962 indicating fumarolic activity, and ashfall was also observed on the southwest of the island indicating that an eruption took place.
KEMP SEAMOUNTS GROUP
The Kemp Seamounts group is a group of undersea volcanoes which are located to the southwest of the Southern Thule Islands, they are Adventure Caldera, Kemp Seamount, and Kemp Caldera. A group of smaller seamounts are located to the west of Kemp Caldera. According to samples collected, the Kemp Seamount is made up out of basalt and basaltic-andesite and the Adventure Caldera is made up out of basalt and dacite. Hydrothermal activity is present at the Kemp and Adventure calderas.
The Nelson Seamounts form the southernmost volcanic centre of the South Sandwich volcanic arc. According to samples collected Nelson is made up out of dacite. Not a lot is known about the Nelson Seamounts given their remote undersea location.
The South Sandwich Islands are quite an active volcanic arc though the most active volcanoes within the archipelago tend to be Mount Curry on Zavodovski Island and Mount Michael on Saunders Island. Most eruptions would most likely be of strombolian style in areas free of ice while eruptions in glacier covered areas would cause a phreatomagmatic eruption. Lava and ice interaction also occurs like the eruptions which occurred on Montagu and Bristol islands which would’ve been similar to the eruptions of Mount Veniaminof in Alaska. The past eruptions of Lucifer Hill on Candlemas Island more likely would’ve been similar to that on Nishino-shima near Japan. If Mount Hodson on Visokoi Island were to erupt from the ice covered summit crater then we would more likely see an Eyjafjallajokull style eruption. And finally if an eruption were to occur in any of the Southern Thule Islands then it would more likely come from a parasitic flank vent, surtseyan eruptions are also a possible scenario if an underwater vent eruption occurred.
Video credit: BBC Planet Earth II
My own knowledge
Global Volcanism Program
Bathymetry and geological setting of the South Sandwich Islands volcanic arc – Philip T. Leat, Peter T. Fretwell, Alex J. Tate, Robert D. Larter, Tara J. Martin, John L. Smellie, Wilfried Jokat, and Gerhard Bohrmann.
The South Sandwich Islands: III. Petrology of the volcanic rocks – P. E. Baker and D. Phil.
Bathymetry and Geological Setting of the South Sandwich Islands Volcanic Arc Side 2: The South Sandwich Islands – Philip T. Leat, Peter T. Fretwell, Alex J. Tate, Robert D. Larter, Tara J. Martin, John L. Smellie, Wilfried Jokat, and Gerhard Bohrmann.
Bathymetry and Geological Setting of the South Sandwich Islands Volcanic Arc Side 1: The South Sandwich Islands – Philip T. Leat, Peter T. Fretwell, Alex J. Tate, Robert D. Larter, Tara J. Martin, John L. Smellie, Wilfried Jokat, and Gerhard Bohrmann.
A little bit about me:
My name is René (or you can call me Ren for short) and I come from the south of England. I’m a volcanophile and a nature lover and have been so since I was a child. To date I have travelled to volcanoes in Sicily, Iceland, Mexico, Guatemala, Costa Rica, Ecuador, and the Galapagos Islands. I also like a bit of photography.
My volcano website: www.volcanoplanet.co.uk
My photography website: www.rgoadphotography.com
My blog about the South Sandwich Islands: http://southsandwichmonitoring.blogspot.co.uk/
55 thoughts on “South Sandwich Islands: volcanic arc in a polar climate”
You wouldn’t perhaps know if there is any update on the penguins on Zavodovski, after the eruption in march? https://www.bas.ac.uk/media-post/penguin-colonies-at-risk-from-erupting-volcano/
Expeditions to the South Sandwich Islands are not so frequent but here is an excerpt from that link: Geographer Dr Peter Fretwell from BAS who was involved in the remapping of the archipelago says:
“We don’t know what impact the ash will have on the penguins. If it has been heavy and widespread it may have a serious effect on the population. It’s impossible to say but two scientific expeditions are scheduled to visit the region from later this year and will try to assess the impact of the eruption.”
I know, that was why I asked, as we are somewhat “later this year” now. I was curious if there was some new info surrounding the subject, considering we are rather late in the year.
Super post, Rene and thank you for bringing us so much information on an area (for me) that I never knew about. Volcano Café goes from strength to strength!
Thanking you. That’s what I like to hear 🙂
According to HVO, Kilauea’s summit seems to have abandoned its DI cycle and has been continuously deflating for the last 5 days (now at 6 microradians); the rate keeps picking up and the lava lake is still dropping in response. Not sure what’s currently happening at Pu’u O’o or rest of rift zones but lava flows and ocean entry still appear to be active. Its quite an abrupt change from the constant net inflation and very high lava lake level of late, but is this significant or just a minor/random anomaly and not noteworthy?
I wonder where it all went. I suspect it won’t take too long before we find out.
It is still within range of what happened over previous years. DI events used to be much longer lasting than recently. It may the depth of overturning is much greater in the current event. Or the earthquakes along the chain of craters has created a new reservoir there that is now filling. Or the awful weather made the lava too wet (ok – that may be less likely). It will reverse again shortly, I expect.
And right on cue it appears it has reversed!
Woot! Personally, I’m a reuben fan, but a Philly cheesesteak can not be passed up.
Good post Rene!
I have thought that it would be fun to have a contest to find how many plumes can be found on Google Earth. Turns out there’s one on Saunders Island:
Three plumes on NASA:
From that distance sometimes it’s hard to tell whether it’s an eruption unless it’s a dirty looking grey or brownish plume.
Bit of a Von Karmen vortex street thing going on at that bottom one, no?
True, and you wouldn’t expected three simultaneous eruptions. It signals heat from the top – volcanic cooling towers
I have always (kinda) wondered if the SSIs are going to become another (albeit colder) Isthmus of Panama … an Isthmus of Sandwiches?
And, wouldn’t that make Antarctica warmer, cutting off the circumpolar circulation?
Is there any evidence that the subduction zone at the South Sandwich Islands is capable of M9 earthquakes? Any tsunami deposits identified anywhere around the South Atlantic?
Great post. I read your blog pretty often.
I’m not quite sure on the earthquake side of things there but I know quakes over the magnitude of 6 does pop up now and again. A 7.2 magnitude earthquake was recorded last May.
Not positive on this, but there was a recent article released stating that one of the major pre-requisities for M9 megathrusts are that the subduction region is located in a non-curved region. Looking at the arc and subduction trench, it seems similarly arc-shaped. I would imagine that this, along with the fact that it’s simply a smaller arc would prevent the size needed to get a m9 level megathrust quake.
USGS has a lookup tool that allows you to plot on a map past historic eq events.
There was a M8.1 event in 1929, more than 60 recorded >M6.5 events since 1900.
Thank you, I am very happy to learn something about this remote area!
Seems like there is not much research done on these volcanoes due to their remoteness. Are there any other above surface calderas, except of Thule? What is the biggest known eruption at these volcanoes? Are effusive and strombolian eruptions the most common types?
Well Belinda Island I’m not sure whether it is a caldera or a plateau covering most of the island. I believe the biggest eruption down at the South Sandwich Islands was the flank eruption on Bristol Island in 1956 with a VEI 3, and yes effusive and strombolian eruptions are the most common eruptive activity there.
Cayambe in Ecuador is restless, signs of rising magma, last eruption 1785-86, has had several ignimbrite-forming eruptions in last few millennia.
I saw this the other day. Definitely one to keep an eye on. I haven’t explicitly seen it written in the update on Cayambe, but this volcano is very similar to Cotopaxi in that it’s a major major Lahar risk. There are some massive glaciers on top of it that lead into narrow valleys and highly populated regions.
More than lahar risk perhaps; that volcano looks decidedly top-heavy and unstable to me – and the long repose period does not bode well.
And based on the past 1000 years of eruptive activity, if it erupts a lava dome there would appear to be a high chance of a VEI-4 eruption. As far as I can tell, the unrest is spread out pretty much right below the area just to one side of that mini-ridge in the centre of the summit icecap in that photo. Not sure which side from that angle, but if it’s to the left, there’s quite a big chunk of the summit which looks a little precarious, especially around the highest ice-free area. The change of location of the swarms from a nearby fault line in June to directly under the edifice now reminds of me of what will probably happen in the buildup to the next eruption of Mount Hood (i.e. a swarm under the summit rather than that fault-line where recent swarms have occurred). Could be interesting if that scenario can be applied here. Another similarity is the timing of this swarm in regards to the previous one (2003-05), which is almost a mirror image of the unrest a decade ago and last year at Cotopaxi. We seem to be in the same boat as then. Anyone’s guess what will happen next! I hope the public are as aware about this as at Cotopaxi last year; the 20,000 people city of Cayambe is very close to the volcano, much closer than Quito is to Cotopaxi.
The repose period technically isn’t all that long if you count the eruption in the late 1700’s, but there isn’t much information on that one, and it may have been phreatic for all we know. With that said, the concern with volcanoes like this is that you don’t need a big eruption for bad things to happen.
With that said, it is definitely at risk for collapse. Couple in viscous dacitic doming with a highly glacially dissected edifice that is likely already quite unstable and you get a volcano that likes to crumble apart as it has done so in the past.
For those interested in following any activity at Cayambe, it can be found at http://www.igepn.edu.ec/cayambe (use Google to translate to english if you need to)s
Or just see images below for deformation / seismicity. Not sure how high the gain is turned up on the current seismograms.
interesting wave on the first line of the seismo. also, the other bumps look pretty “wet”??
Yeah, not sure if that’s something local or distal however.
For whatever it’s worth, here what the drum plot looked like when it had the m3.6 earthquake for the sake of comparison.
6.8 earthquake off the coast of Northern California
M6.8 off Ferndale, the earthquake capital of the lower 48. Great place to visit if you like kinetic art, Victorian houses and the engineering of earthquake-resistance construction.
Don’t want to sound alarmist but could this be a prelude to something much larger?
This is a fairly separate segment from the locked subduction zone there. It could technically imply that more stress is being pushed onto the subduction trench, but that is more or less always the case as time passes. Not an expert on earthquakes, but I wouldn’t imagine this being all that big of a deal.
Yep just the Mendocino Triple Junction doing its
quake thing it was out on the Gorda ridge anyway,
More worried about the two 4.0+ and the 2.4 last week off the coast of Coos Bay-the Cascadia’s
more likely to be involved..
I don’t think there’s anything to worry about. The axial seamount volcano is most always making noise. It’s roughly 250 miles off the coast of Oregon. At roughly three fourth miles depth. A very interesting huge volcano. (response to tgmccoy, encase this post doesn’t go where it should lol)
“off the coast of Coos”
… if so, they can kiss that bridge goodbye. Even with reinforcements it isn’t going to fare very well.
Got as far away as I could from that place. One of the biggest farces is that
the “Tsunami escape route”signs pointing over the McCollugh bridge..
Hekla is stirring things up:
08.12.2016 11:59:11 63.992 -19.690 0.6 km 0.0 99.0 1.1 km W of Hekla
I wonder what a magnitude 0.0 earthquake feels like.
Feels like small (tiny) vibration, but one needs extra sensitive and concious mind to realize
its a quake. Standing next to Holuhraun one felt the earth vibes in the earth and small camera
shake shows up.
FEI (For everyones info), It has come to light in my mind why no flooding occurred when the five small eruptions happened under the Bárðarbunga Glacier, just before Holuhraun.
1.) They were small, lava only driven by gravity and escaping volcanic gas pressures.
2.) Meltwater has more density than snow or Ice (occupies less volume), melt remained in place and probably bleed off slowly as time goes by (no increased conductivity was measured in rivers), but “roof” over them collapsed and formed the “cauldrons” (indentations in the glaciers surface).
Them “flood warnings” used to close off large areas of land, for months, but in hindsight, in my view, were misuse of authority.
If you are correct then the ‘flood warnings’ may have been a mistake … but there’s a wide gulf between a mistake and ‘misuse of authority’. They were given the authority and they used it as designed. No ‘misuse’ here.
“Misuse of authority” seems hyperbolic … even assuming that your theory holds water 😉
I do say, because very large areas of the interior NOT at any level flood risk were closed too and ALL access denied. Allowed people on the area was “one Puma helo load” (!) And Road access route specified was the longest possible to drive, and very slow to travel, both from the capital, and also crossed the most at risk river banks areas!
Flood warning was a ruse, surprisingly I personally heard lead-scientist blatantly “thay wanted the area closed, so they could have it” (to themselves).
Both local and international media people did complain a lot, and still do as ayuthority here is using closures as form of control, not having to deal with reporters, which are the eyes and ears of the people. If their eyes are shut grave things can and usually happen, curruption and concealment togeather.
But this situation is also in politics etc. here. No big deal.
Yeah …. peace out. I don’t know how to begin to parse that. The anti-scientist undertone is almost trumpian.
Sadly science and politics have a complex relation. When science discovers something worth money, politics quickly takes credit and is happy. When it discovers something that will cost money, they get vilified by politics. Trumpian? I hope not but as someone said, a pessimist is what an optimist calls a realist. The signs are pointing at trouble.
Large areas of the interior were closed because of the risk from gas – and from the possibility of a sudden increase in the eruption if it started in the caldera – and not wanting to have to deal with sightseers getting lost or in trouble in pretty hostile terrain. I know. I was there. I had a pass issued by the Almannavarnir. I spent three weeks filming the eruption. I spent a day at the police headquarters in Husavik – they spent a lot of time looking for a foreign journalist who was lost in the closed area after breaking the rules and going off on his own without his Icelandic guide.
It was a very well-run eruption.
“It was a very well-run eruption.”
Now there’s a phrase that one does not encounter very often. 🙂
Magnitude M 8.0
Region SOLOMON ISLANDS
Date time 2016-12-08 17:38:46.7 UTC
Location 10.60 S ; 161.32 E
Depth 40 km
Severe quake in Solomon Islands, Hawaii under TSUNAMI WATCH
Look at this map 16 buoys now in Tsunami mode :
This was a large earthquake, in a region particular prone to them. The depth was probably too large for major tsunami activity, and the islanders are familiar with major quakes. There are a lot of volcanoes in the area, including (just) subsea Kavachi. Did any respond to the earthquake?
6.9 mg now.
Magnitude Mw 6.9
Region SOLOMON ISLANDS
Date time 2016-12-09 19:10:08.6 UTC
Location 10.74 S ; 161.08 E
Depth 30 km
New post is up! From the beauty of the South Sandwich to the science of experimental history
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