Raikoke volcano in the Kurils erupted around 0400 L on June 22, 2019. The eruption was observed by Space Station astronauts, the MODIS instrument on NASA’s Terra satellite, GOES West, Suomi NPP / VIIRS, Copernicus Sentinel5P and Himwari-8. There were at least nine distinct pulses of ash injection due to significant explosions. The plume was drawn eastward into a storm system making its way up the Aleutians. The most violent portion of the eruption sequence was over in less than 24 yours.
One of the things satellite and visual photography gives us is the ability to see volcanic plumes as they develop. Photographic coverage of this eruption was combined into animated GIFs and short videos similar to the multiple images of Sarychev taken from the Shuttle June 12, 2009. Over the course of the last decade, scientists are getting much better at it.
Outside of various Twitter feeds linked in the Additional Information section, the NOAA CIMSS Satellite Blog has the best compendium of satellite observation products and animated GIFs of this eruption.
Raikoke is a small volcanic island in the central Kuril islands, 16 km across the Golovnin Strait from Matua Island, home of Sarychev volcano which we covered in May. It is a remote island, with less than 150 people within 100 km of the island.
It is a circular island nearly 5 km in area, topping out at 551 m above the ocean surface. It has a crater on top 700 m in diameter.
Like most other islands in this part of the world, Raikoke is uninhabited and home to bird and seal rookeries. It is (was?) one of the five major Steller sea lion rookeries in the Kuril Islands. It is home to nesting populations of various sea birds.
There were reports of 15,000 northern fur seals on the island in 1883. It took seal hunters only a decade to reduce that number to “a few scores.” Currently no fur seals reproduce on Raikoke.
Indigenous Japanese Ainu visited Raikoke with hunting and fishing parties. There was no permanent habitation on the island at the time of European contact. It was initially part of feudal Japan. Ownership went back and forth between Russia and Imperial Japan until the Kurils were captured by the Soviet Union in the latter stages of WWII.
Raikoke Island is a small basaltic island that has not been particularly active over the last 400 years. Smithsonian GVP lists three previous eruptions, a VEI2 in 1765, a VEI 4 which removed the top third of the island in 1778, and a recent VEI 4 in 1924. The June 22 eruption has also been classified as a VEI4.
The most recent eruption began early morning on June 22. There were a series of at least nine explosions putting a plume as high as 13 km above the volcano. Six of the explosions were within the first half hour. The plume drifted to the east and was wrapped into a major storm system working its way along the western Aleutians. The eruption had a significant SO2 component that did not disperse and was visible via satellite observations as it wrapped around the storm’s center. Tropopause altitude at the time was 11 km, so the top of the plume made it into the stratosphere. CALIPSO data suggests parts of the plume may have reached 17 km.
The VaisalaGroup responded to a Klemetti Tweet with a note that almost 600 lightning events were detected since the start of the eruption.
In response, KVERT and SVERT raised the aviation color code to Red. 24 hours later, the leading edge of the plume had traveled 2,000 ENE. The Tokyo VAAC and Alaska Volcano Observatory also issued aviation warnings. In all, there were at least 40 flights diverted due to the eruption.
Although the main event ended in over the course of the first 12 hours of eruption, plumes were still visible the next day rising 4.5 km above the volcano.
A passing ship sent out a drone that returned video and photos of the island. The entire island was covered in light colored ash, some of it up to several meters thick in places. In some locations, wave action interacted with the pyroclastic flow deposits causing steam explosions and emissions. Minor ashfall was reported 340 km NE by that evening.
Ash plumes continued through June 25, though they were only 2 km high. Prevailing winds still carried the ash to the NW.
The eruption produced pyroclastic flows and ashfall that changed the shape of the island, growing it a bit at least for a little while.
The short description of tectonics in this part of the world is that it is driven by the subduction of the Pacific Plate under the Okhotsk Sea plate. The Kuril Trench is offshore to the east with the movement of the Pacific Plate being about 8 cm/yr. Volcanic activity is all subduction driven and there are large megathrust earthquakes in the region.
Raikoke is an infrequently active volcano. When it erupts, it does get its money’s worth, with the three most recent eruptions all in the VEI 4 range. It is currently uninhabited and the eruption disrupted nesting grounds and rookeries for birds and seals at least for a while.
Timing of this eruption was also interesting, as there was another VEI 4 out of Ulawun in New Britain, PNG on the same day, leading some to opine that this was the first time two eruptions that large were observed on the same day.