Alaid: Part 2 – rising from the sea and 2 riddles!

From a distance Alaid appears to be a regular stratovolcano, but its collapsed summit crater and flank cones (a crater row can just be seen at extreme right) make it more complex (© L. Kotenko via KVERT)

Alaid’s summit stands 2339 metres above sea level, making it the tallest volcano in the Kuril chain. It rises up from a sea bed that is around 750 metres deep, making its overall height in the region of 3000 metres – quite a giant. Its birth dates to around 40,000 to 50,000 years ago, and it is classed as a Somma-Vesuvius type stratovolcano, with a resurgent 250-metre cone having grown inside the partially collapsed central crater.

In a sparsely populated area with few written records Alaid’s history prior to the 20^th century is little known, and even recent events have gone unnoticed or unconfirmed due to the remoteness of the location and the poor weather that can often shroud the summit for days on end. Alaid is known to have had mainly explosive eruptions from the summit crater in 1790-93, 1854, 1860 and 1894. The eruption of 1790-93 was considered a large event, and was given a VEI4 rating.

Alaid is noticeably different to other Kuril volcanoes, and not only on account of its large size. For a start, it lies behind the main island arc of volcanoes, while its magmas are predominantly high-aluminium, high-iron basalts, with very little evidence of more evolved andesites. Alaid’s nearest active sub-aerial neighbour is Ebeko, which is located around 37 km to the ESE on Paramushir island along the main arc. Ebeko is much younger, an active and typical subduction volcano producing andesites and andesitic basalts.

Alaid also has at least 36 parasitic cones on its flanks, including those underwater. Such features are rarely found on other Kuril volcanoes. Furthermore, the mineral traces in waters of the geothermal area that was created in the 1972 eruption are very different to those from geothermal areas in the main island arc.

Alaid has a baby!

Although the presence of large numbers of cones is evidence of a history of radial fissure and excentric vent activity, this was not observed until an eruption that began on 13^th November 1933. The activity began underwater just off the east coast of the island and led to the creation of a new cone that rose from the sea just offshore. The eruption continued until August 1934, and left behind a new island that was soon joined to the shore by a narrow isthmus of volcanic sand. The new land was called Taketomi and today it clings to Alaid’s side, erosion having reduced the joining spit to a razorbacked sliver.

Taketomi was formed by an underwater flank eruption. The crater is joined to the shoreline by a narrow spit of sand (© R.V. Zigacheva via KVERT)

The Olympics eruption

The four craters and lava delta formed by the 1972 eruption (© V.A. Rashidov/IVS DVO RAN via KVERT)

Alaid was quiet for the next few decades, but sprung into life again on 18^th June 1972. Again this was a flank eruption, but this time in the northwest of the island. Four explosive vents (maars) opened up along a radial fissure, one of which measured around 500 metres in diameter. Lava issued mainly from the two lower vents and then ran to the sea, where it increased the island’s area through the formation of a lava delta that extended the coastline by about 300 metres at its maximum point. From one of the maars a cinder cone grew, eventually reaching a height of around 80 metres. Explosive activity ceased on 15^th August and lava stopped flowing on 11^th September. A crater row was left behind, named the Olimpiyskiy cones (the Munich Olympic Games were under way during the latter part of the eruption).

During the 1972 Olimpiyskiy flank eruption lava flowed into the sea to extend the area of the island by about 1 square kilometre. Here the lava steams as it meets the sea, while the vents behind continue to smoke (© V.A. Podtabachny/IVS FED RAS via KVERT)

Thanks to Beeld en Geluid here is a short film (with Dutch narration) about the 1972 eruption, complete with a fox (the island’s largest inhabitant) and the obligatory crazy Russians walking around on hot lava.

Major eruption of 1981

In the early afternoon of 27^th April 1981 Alaid exploded into its biggest eruption since the 1790-93 event. It began with a small steam plume, but explosive activity increased rapidly in magnitude to build a black ash column. The eruption further intensified the next day, and three large explosive blasts were recorded by microbarographs at Kushiro, 1250 km away to the southwest. Over the next two days a dense plume around 1900 km long was formed, the column reaching to an altitude of 13000 metres. On 1^st May the main plume feed came to an end.

In the initial stages of the eruption the ash cloud was reportedly too thick for aircraft to approach, but as soon as the plume settled into a more stable state geologists flew to the area
(© V.A. Podtabachny/IVS FED RAS via KVERT)

Ejected ash, comprising a pyroxene olivine basalt, fell over an area calculated as 150,000 km^2. On the island’s shore more than 30 cm accumulated, and small lahars formed as ash mixed with snow and ice. In the town of Severo-Kurilsk, 45 km away to the ESE on the island of Paramushir, residents heard the volcano’s roar and could see a glow by night. Soon the ash began falling, and up to 25 cm accumulated, leading to some disruption.

As the plume headed northeast, ash mixed with wet snow fell on the Kamchatkan town of Petropavlovsk at a distance of 300 km from Alaid, and ashfall was recorded as far away as the US military outpost of Shemya, 1200 km away in the Aleutian island chain.

Another view shows how Alaid’s ash plume divided into a more diffuse lower altitude element, and a denser upper component (© V.A. Podtabachny/IVS FED RAS via KVERT)

On 29^th April the wind changed direction to ESE, taking the plume out over the Pacific. Over the next days activity declined significantly, and ceased temporarily on the 7^th. On the next day, however, Alaid produced another sizeable eruption column. The plume was not as large as that produced by the initial eruption, reaching only 400 km in length.

Further eruptive phases took place in the coming days, producing plumes of varying lengths. Activity was continuous from 15^th to 27^th May, at times the plume reaching nearly 600 km in length. By the time the eruption ended on 5^th June it had pumped an estimated 5.5 x 10^8 cubic metres of tephra into the atmosphere.

This view of the ash plume from the 1981 eruption was recorded by the NOAA 6 weather satellite (National Oceanic and Atmospheric Administration)

While the US NOAA 6 and Japanese GMS satellites provided some imagery of the eruption plume, when weather permitted, the 1981 eruption was also tracked by NASA’s then relatively new TOMS (Total Ozone Mapping Spectrometer) sensor. This was carried by the Nimbus-7 satellite and had gone ‘live’ on 31^st October 1978, in time to provide data from the Mount St Helens, Krafla and Hekla eruptions in 1980. NASA was able to track the distribution of aerosols and the sulfur dioxide cloud from Alaid as it spread across North America in the days after the initial explosive event.

A daily sequence of TOMS imagery tracks high levels of sulfur dioxide from the 1981 eruption. There are two distinct SO2 clouds, one which tracks northeast and over Alaska and northern Canada, while a later cloud tracks east and largely dissipates over the Pacific Ocean (NASA)

Alaid’s faithful companion

On the surface, at least, Alaid stands alone, but appearances can be deceptive. In the decade following the 1981 eruption the Vladivostok-based Soviet research vessel Vulkanolog conducted a survey of the area, mapping the seabed’s profile and magnetism, and collecting dredged samples for analysis. The seas around Atlasov Island were of particular interest, particularly Alaid’s companion that lies hidden beneath the waters.

Topography/bathymetry of northern Kurils
(© KVERT, annotations by author)

Just to the northwest of Alaid stands another volcano, its summit submerged beneath the sea. Named Grigorieva, after geologist I. F. Grigoriev*, the submarine volcano’s peak is around 10 km distant from that of Alaid. Analysis of samples showed that Grigorieva’s rocks are similar to those of Alaid, although it is considered as a separate volcano in its own right, despite the fact that its base has merged with that of Alaid. With its peak at a depth of around 140 metres, it is quite likely that Grigorieva once breached the surface during the time of the most recent glacial maximum. Like its sub-aerial companion, Grigorieva has a high number – at least 13 – of extrusive lava domes on its slopes.

Much further to the northwest is the Lebedya (swan) bank, another raised area of seabed. It has been suggested that Alaid, Grigorieva and Lebedya could be related, representing a side-spur of volcanic activity that lies perpendicular to the main plate boundary that drives most Kuril activity.

• Iosef Fedorovich Grigoriev was a geologist specialising in ore deposits who became a key figure in the dramatic rise in military industrial output during the Great Patriotic War (1941-45). At the end of hostilities he became the chief geologist leading the task of developing a uranium mining operation in Krasnoyarsk territory to provide fuel for the Soviet Union’s nascent nuclear weapons programme. On 31^st March 1949 he was arrested, with other senior geologists, on the basis of untrue allegations that he had concealed details of uranium deposits. For years the official story held that he was tried, convicted and sentenced to the gulag, where he died in 1951. In fact, he died on 14^th May 1949 while being transferred back to his cell following an interrogation session, just six weeks after his arrest. His honour and reputation were fully restored in 1954.

Recent activity

During the April 1981 eruption a new cone grew in the summit crater, seen here in June as the eruption came to an end. In 1986 the cone partly collapsed – compare with later photos of the main crater (© A.A. Ovsyannikov/IVS FED RAS via KVERT)

Since 1981 Alaid has been restless. Small explosive eruptions at the summit crater have been recorded in March 1982, May 1986, December 1996 and August 1997. During the 1986 event much of the 60-metre high central scoria cone that had arisen in 1981 collapsed. There may have been other minor events, with some seismic and thermal evidence to suggest them, but nothing was actually seen, and high winds in the area have often produced readings that could be interpreted as volcanic tremor.

Last year the volcano again showed more than a glimmer of life. On 5^th October a gas-steam plume containing some ash was noted rising several hundred metres from the summit, and similar episodes were recorded throughout the month. At the same time, snow on the mountain sides began to acquire a thin coating of ash deposits, and a small cinder cone was noted to have grown in the summit crater. Seismic activity was noted by KVERT in late November as ‘moderate’, with volcanic tremor rising to 18.7 mcm/s. From early December activity dropped off, and Alaid appears to have gone back to sleep. Its aviation status was reduced to green in January.

A fly-by of Alaid’s summit on 27th October 2012 showed fumarolic activity. The volcano showed signs of unrest into December (© A. Sokorenko/IVS FEB RAS via KVERT)

While this low-level activity appears to be quite normal for the volcano, the eruption of 1981 showed that Alaid has the potential to create considerable havoc to air traffic in the region. It is alive, ashy and explosive: definitely one to watch in the coming years!

UKViggen

Thanks to KVERT for permission to use images from the agency’s website (http://www.kscnet.ru/ivs/kvert/index_eng.php)

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Update:

Alan C’s Evil Riddle:

My true dusky identity was hidden! My secret lies in my blackness! Confused?
What am I?
Who are my relatives?
Where can I be found?

Clue:

Pay an old Greek a visit! He may let the cat out of the bag!

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Update #2:

NtV (Name that Volcano)Riddle

1 point for each volcano; RED HERRINGS now shown in bold!

No 1 – Lethal lahars; Starry siblings; Satellites; Volcanic group;
No 2 – Mild vulcanian; Cargo Cult leader ‘residence’; Lava bombs; 1874; SOLVED .. Mount Yasur
No 3 – 1927 German Silent movie; Northern Europe; Legend of ill fated lovers; Two calderas;
No 4 – Flank fissure eruptions; c4 mile glacier; 1921; Emperor penguins; SOLVED .. Beerenberg

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