olelog

Since last week I have been trying to figure out just where a mysterious new volcano eruption in the red Sea had taken place. A satellite image has now stilled my curiosity.

Last week fishermen reported that they had seen lava fountains rising 20-30 meter near the Zubair islands about 50 km west of Salif, in Yemen. The exact location was however unclear. The eruption apparently lead to the birth of a new island, which can be seen on this satellite image fro NASA Earth Observatory.



The activity in the Red Sea included more than one eruption. By 23 December 2011, what looked like a new island appeared in the region. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this high-resolution, natural-color images on 23 December 2011. The image shows an apparent island where there had previously been an unbroken water surface. A thick plume rises from the island, dark near the bottom and light near the top, perhaps a mixture of volcanic ash and water vapor. The volcanic activity occurred along the Zubair Group, a collection of small islands off the west coast of Yemen. Running in a roughly northwest-southeast line, the islands poke above the sea surface, rising from a shield volcano. This region is part of the Red Sea Rift where the African and Arabian tectonic plates pull apart and new ocean crust regularly forms.

Four years ago there was a similar eruption at the Yemeni Jabal al-Tair island.



These volcanoes are situated at the Red Sea Rift, a spreading ridge between two tectonic plates, the African (or Nubian) Plate and the Arabian Plate. It extends down the length of the Red Sea, stretching from the southern end of the Dead Sea Transform to a triple junction with the Aden Ridge and the East African Rift (the Afar Triple Junction) in the Afar Depression of eastern Africa. The rift zone indeed includes the island of Jabal al-Tair, formed by the basaltic stratovolcano of the same name, located northwest of the Bab al-Mandab passage at the mouth of the Red Sea, about half way between Yemen and Eritrea, a volcano that erupted on 30 September 2007 after 124 years of dormancy.

• http://earthobservatory.nasa.gov/IOTD/view.php?id=76801&src=eoa-iotd
• http://theextinctionprotocol.wordpress.com/2011/12/20/volcano-erupts-in-yemen-spewing-lava-a-first-for-the-region-says-locals/
• http://www.volcanodiscovery.com/view_news/4217/Volcanic-Eruption-in-the-Red-Sea-Yemen-reported.html
• http://www.yobserver.com/local-news/10021711.html
• http://apparitionsourlady.blogspot.com/2011/12/yemen-volcano-awakens-saba-island.html
• http://www.accuweather.com/en/weather-news/yemen-volcano-eruption-reporte/59286?utm_source=dlvr.it&utm_medium=twitter
• http://www.wired.com/wiredscience/eruptions

See also my 2007 post

Geology.com drew my attention to a marvellous satellite image that NASA's Earth Observatory published in 2009.



Please note that north is to the right. The image shows the Tao-Rusyr Caldera at the southern end of Onekotan Island, Kuril Islands, Russia. The 7.5 km wide caldera was formed during an explosive eruption less than 10,000 years ago (reported ages range from 5550 to 9400 Before Present). The waters of Kal'tsevoe Lake fill the caldera, along with a large symmetrical andesitic cone, Krenitsyn Peak, that rises as an island within the lake. This volcano was named after Captain Pyotr Krenitsyn of the Imperial Russian Navy. The most recent, and only historical eruption, in 1952, formed a small lava dome on the island's east coast. Krenitsyn Peak has a summit crater 350 m wide and is the highest point (1,325 m) of the volcano and on the entire Onekotan Island. Another caldera, Nemo Peak, lies at the northern end of the island, and it also contains a central cone and crater lake. A relatively flat isthmus connects the two stratovolcanoes, Krenitsyn and Nemo.

I think I also owe you an image (from NOAA) of the Tao-Rusyr Caldera from the ground:



Onekotan (Russian: Онекотан) is an uninhabited volcanic island located near the northern end of the Kuril Islands chain in the Sea of Okhotsk in the northwest Pacific Ocean. Its name is derived from the Ainu language for "large village". Onekotan is roughly rectangular, with a length of 42.5 km, and a width ranging from 11 km to 17 km. It has an area of 425 km².

The Kuril Islands is a volcanic island arc that stretches approximately 1,300 km northeast from Hokkaidō, Japan, to Kamchatka, Russia, separating the Sea of Okhotsk from the North Pacific Ocean. The volcanic arc continues in the Kamchatkan Peninsula which is famous for its many volcanoes. The Kurils count 56 islands and many more minor rocks. All of the islands are now under Russian jurisdiction, but Japan claims the four southernmost as part of its territory (occupied by Russia since World War II). Below is a map of the islands showing the de facto division between Japan and Russia over time (Image from Wikipedia).



The Kuril Island volcanoes are fueled by magma generated by the subduction of the Pacific Plate under the Eurasian Plate, which takes place along a deep trench about 200 km to the islands' east. Large earthquakes at the Kuril Trench may lead to tsunamis. The 1952 Severo-Kurilsk Tsunami was a major tsunami that hit Severo-Kurilsk on the (larger) island of Paramushir north of the Onekotan Island. It occurred on 5 November 1952 at about 5 a.m. It led to the destruction of many settlements in Sakhalin Oblast and Kamchatka Oblast, while the main impact struck the town of Severo-Kurilsk (See google map below). The tsunami was generated by a major earthquake in the Pacific Ocean, 130 km from the shore of Kamchatka, with an estimated magnitude of 8.5. There were three waves about 15-18 m high.

Finally a google map with Onekotan, Severo-Kurilsk on Paramushir, and the Kuril Trench (Dark blue):



and my marking of the location of the two calderas/volcanoes on Onekotan island:

• http://earthobservatory.nasa.gov/IOTD/view.php?id=40891
• http://geology.com/nasa/onekotan-island/
• http://www.volcano.si.edu/world/volcano.cfm?vnum=0900-31=
• http://www.drgeorgepc.com/Tsunami1952.html

There are numerous volcano islands in the Pacific Ocean. A small group of Japanese islands are even named the ‘Volcano Islands’, or 火山列島, Kazan Rettō in Japanese.



The group consists of three islands south of the Bonin Islands, and are all active volcanoes lying atop an island arc, the Izu-Marianas arc, that stretches south to the Marianas. Their names are: Kita Iwo Jima (北硫黄島), Iwo Jima (硫黄島), and Minami Iwo Jima (南硫黄島}.



Kita Iwo Jima consists of the heavily eroded peak of a stratovolcano, which rises 792 m above sea level. An Undersea volcano, Fukutoku-Okanoba, in the Volcano Islands erupted in February 2010.



The Izu-Bonin-Mariana (IBM) arc system extends over 2800 km. Much of the IBM arc system is submerged below sealevel. The IBM arc system lies along the eastern margin of the Philippine Sea Plate in the Western Pacific Ocean. The IBM arc system formed as a result of subduction of the western Pacific plate. The IBM arc system now subducts mid-Jurassic to Early Cretaceous lithosphere, with younger lithosphere in the north and older lithosphere in the south, including the oldest (~170 million years old) oceanic crust. Subduction rates vary from ~2 cm per year in the south to 6 cm in the north.

• http://en.wikipedia.org/wiki/Izu-Bonin-Mariana_Arc

PS:
The Japanese characters may not show up on your PC. My best advice is to buy a Mactintosh| - Using another browser may also do the trick ;-)

I got interested in the Columbia supercontinent when I visited the Ketilides (ancient mountain range) in southern Greenland in 2003. This pre-Rodinia supercontinent has also been known as Nuna and Hudsonland or hudsonia, but Rogers dubbed it Columbia in 2002.

Rogers named the supercontinent Columbia because some of the best evidence for its existence was in the Columbia River region of western North America. In the shown configuration of Columbia, proposed by Rogers and Santosh, South Africa, Madagascar, India, Australia and attached parts of Antarctica are placed adjacent to the western margin of North America, whereas Greenland, Baltica (Northern Europe) and Siberia are positioned adjacent to the northeastern margin of North America, and South America is placed against North West Africa (the two together forming a continent dubbed Amazonia). This reconstruction shows an extremely long subduction zone (saw-tooth line).

Palaeomagnetic reconstruction of continents that may have existed nearly two billion years ago is far from easy. Here is a similar reconstruction by Pesonen and colleagues.



Here Amazonia is shown in two possible positions and Baltica is rotated in respect to Rogers’ reconstruction. I find this latter reconstruction particularly interesting, as it would place both the southern tip of Greenland and the west coast of Norway in a subduction zone around 1830 million years ago leading to mountain building in both places. In how far Baltica was rotated in the past is still open for discussion.

The Ketilidian orogeny is one of several Palaeoproterozoic orogenies in West Greenland. The Ketilidian orogeny correlates westward with the Makkovik system in eastern Labrador. The Ketilidian orogeny was accreted to the southern margin of the Archaean West Greenland craton about 1800 million years ago in a transpressive convergent setting with subduction from the south. This orogeny may thus have been simultaneous with and caused by the same subduction as what has been termed the “Nordic Orogeny” in Scandinavia.

The Columbia supercontinent has been featured in quite a few publications in 2010, mainly in connection with research in Asia. Let me just name a few:

• Yang et al.: Mesoproterozoic mafic and carbonatitic dykes from the northern margin of the North China Craton: Implications for the final breakup of Columbia supercontinent
• Singh et al.: SHRIMP U-Pb c. 1860 Ma anorogenic magmatic signatures from the NW Himalaya: implications for Palaeoproterozoic assembly of the Columbia Supercontinent
• Kaur et al.: Zircon ages of late Palaeoproterozoic (ca. 1.72–1.70 Ga) extension-related granitoids in NE Rajasthan, India: Regional and tectonic significance
• Santosh et al.: Counterclockwise exhumation of a hot orogen: The Paleoproterozoic ultrahigh-temperature granulites in the North China Craton

One of the most prominent among the active volcanic arcs in the Philippine Mobile Belt is the Bicol Arc, a ~260 km long volcanic arc located in the central-eastern margin of the Philippine Mobile Belt. The Bicol Arc hosts three of the active volcanoes (Mayon, Iriga and Bulusan) in the country, including the Mayon Volcano, which has erupted repeatedly within the last decade. The Bicol Arc is named after the Bicol Region (see map). Aside from the three active volcanoes, there are at least nine other Pleistocene major volcanic centers that make up the volcanic arc. Although the rocks from the arc range in composition from basalt to rhyolite, they are mostly basaltic andesites and andesites. Mayon, Iriga and Bulusan are respectively marked as M, I and B on the Google map below.




A volcanic arc is a chain of volcanoes formed as an oceanic tectonic plate (in this case the Pacific Plate) subducts under another tectonic plate (here the Philippine Plate) and produces magma at depth under the over-riding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone.

The volcano Bulusan, was constructed within an 11 km diameter dacitic caldera, which was formed more than 36,000 years ago. Bulusan is flanked by several other large intracaldera lava domes and cones. The summit of Bulusan volcano is unvegetated and contains a 300 m wide, 50 m deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century.

On 7 November 2010 increased seismic activity was recorded at Bulusan Volcano, 24 hours after the active volcano spewed a 600 m ash column and grayish steam on 5 November 2010. Volcanologists noted that at least 10 volcanic earthquakes and four explosion-type events have been documented subsequent to the emission of ash and steam Saturday morning 5 November 2010. It was also noted that steaming activity was characterized by strong emission of a white steam column that reached a maximum height of 200 m above the crater rim. The public was warned not to enter the four-kilometer permanent danger zone from the volcano. People residing near the valleys and streams were also advised to be extra alert against sediment-laden stream flows in the event of heavy rains. More ash ejection were reported on 8 and 9 November 2010 with ash fall on areas in Juban and Irosin towns in Sorsogon province. A bulletin on 9 November 2010 stated that eight volcanic earthquakes were recorded from the volcano during the past 24 hours and weak to moderate emission of ash explotion was observed. Residents near valleys and streams were also warned against sediment-laden stream flows in the event of heavy and continuous rainfall.

During 10-11 November 2010 18 volcano tectonic earthquakes from Bulusan were detected by the seismic network. On 11 November white steam plumes rose 150 m above the Bulusan crater. During an aerial survey, scientists saw that recent explosions resulted in the joining of two craters from 2006-2007 into one. They also noted that deposits from an explosion on 9 November did not contain juvenile material. On 12 November an ash explosion produced an ash-and-steam plume that rose 700 m above the crater. Multiple neighbourhoods reported light ashfall. Four volcano-tectonic earthquakes were detected during the previous 24 hours. Steam plumes rose to a maximum height of 100 m above the crater. Some steaming was seen during 13-14 November. White steam rose from the NW vent, but no steaming was observed from the crater and SE vent on 14 and 15 November. An explosion late at night on 15 November was followed by ashfall in nearby neighbourhoods. Cloud cover prevented observations of the summit area the next morning.

For more details on the current activity see Erik Klemetti’s Eruptions blog a.o. at http://bigthink.com/ideas/25127

The latest news I have seen at the time of writing is that the National Risk Reduction and Management Council in its latest bulletin released 5 p.m. Wednesday 24 November, reported an ash explosion in Mt. Bulusan at 1:24 p.m., with ash reaching up to 1,000 m high above the volcano’s crater. The ash ejected by the volcano drifted in the southwest direction, although state volcanologists said there were no major emissions of steam and sulfure dioxide gas observed around the volcano. Because of this, Alert Level 1 remains in effect over Mt. Bulusan. Residents around the area were also asked to continue avoiding the four-kilometer permanent danger zone around the volcano. 2,827 families have already been forced to leave their homes due to the volcano’s heightened activity.