Chikurachki erupted explosively on February 16, 2015. The plume reached 7.5 km (25,000 ft) on 16 February, itself, and 3.6 km to 4.5 km on February 17 and 18.
The Earth Observatory, NASA, published this image of the eruption plume:
Fig 1: Plume on February 17, 2015. Source: http://earthobservatory.nasa.gov/IOTD/view.php?id=85321
Chikurachki is a 1,816 m high active stratovolcano with a shallow summit crater located at the northern end of the Karpinsky Ridge on Paramushir Island in the northern Kuriles. Wikipedia describes Paramushir Island as a volcanic island made up of a continuous chain of 23 volcanoes, of which at least five are active: Chikurachki, Fuss Peak, the Karpinsky Group, the Lomonosov Group and Ebeko. The island has a subarctic climate with alpine tundra vegetation: Siberian dwarf pines, shrubby alder, edible mushrooms and berries (lingonberry, Arctic raspberry, whortleberry and crowberry). Fauna include red fox, arctic hares, ermine and brown bears.
Fig 2: Chikurachki, with the Karpinsky Ridge behind her on the left of the image and Fuss Peak behind her to the right of the image. Source: Google Earth.
Fig 3: Karpinsky Ridge, Paramushir Island. Source: Google Earth
Chikurachki is part of the Chikurachki – Tatarinov complex. Chikurachki is a young cone on an older Pleistocene volcano, with a distinctive red colour from oxidised basaltic /andesitic scoria. Tatarinov is heavily eroded and appears to have had only one eruption in historical time, although Tatarinov’s southern cone has evidence of possibly more recent activity – a sulphur encrusted crater which had fumerolic activity until 1959. Recorded activity on Chikurachki started around 7,500 BC. GVP reports 23 confirmed eruptions for her in the Holocene; VEIs have been provided for 21 of these: 2 were VEI-1; 12 were VEI-2; 2 were VEI-3; and, 5 were VEI-4. The VEI-4s occurred in 6310 BCE, 1950 BCE, 1500 BCE, 1690 and 1986.
Chikurachki’s tectonic setting is continental crust (>25km) in a subduction zone. Here the Pacific Plate is subducting under the Okhotsk Plate.
Fig 4 : Okhotsk Plate and Paramushir Island. Source: http://commons.wikimedia.org/wiki/File:Okhotsk_Plate_map_en.png Published under Creative Commons License 
Plotting the earthquakes in the area published by IRIS, clearly shows the subducting Pacific Plate.
Fig 5: Plot of the earthquakes from IRIS showing the subducting plate. Copyright rests with the author; reproduced here with her kind permission.
Despite volcanic activity being driven by subduction, Chikurachki’s lavas are basalt / picro-basalt and andesite / basaltic andesite. According to a study by T. Hasegawa et al., the lavas of the Chikurachki are medium K, basalt-basaltic andesite, with a smooth transition from mafic to more felsic based on SiO2 – oxide diagrams, suggesting that fractional crystallisation was a main factor in development of her magma system.
Basaltic volcanoes do not tend to produce Plinian eruptions so Chikurachki is considered a little unusual. A.A. Gurenko et al. attribute a high concentration of water in Chikurachki’s magmas as being the most likely cause of the most recent Plinian eruptions (1853 and 1986).
Hope you enjoyed reading this. The usual caveats apply: “not an expert, etc…”
KarenZ, March 2015
- Earth Observatory, NASA: http://earthobservatory.nasa.gov/IOTD/view.php?id=85321
- GVP, Chikurachki: http://volcano.si.edu/volcano.cfm?vn=290360
- Paramushir Island: http://en.wikipedia.org/wiki/Paramushir
- Takeshi Hasegawa, Mitsuhiro Nakagawa, Mitsuhiro Yoshimoto, Yoshihiro Ishizuka, Wataru Hirose, Sho-ichi Seki, Vera Ponomareva, Rybin Alexander: “Tephrostratigraphy and petrological study of Chikurachki and Fuss volcanoes, western Paramushir Island, northern Kurile Islands: Evaluation of Holocene eruptive activity and temporal change of magma system”, Quaternary International 246 (2011) 278-297.
- A.A. Gurenko, A.B. Belousov, R.B. Trumbull, A.V. Sobolev: “Explosive basaltic volcanism of the Chikurachki Volcano (Kurile arc, Russia): Insights on pre-eruptive magmatic conditions and volatile budget revealed from phenocryst-hosted melt inclusions and groundmass glasses”, Journal of Volcanology and Geothermal Research 147 (2005) 203– 232.
- Map of the plates from a derivative work:Psbsub (talk), source: http://commons.wikimedia.org/wiki/File:Tectonic_plates_boundaries_detailed-fr.svg .published under creative commons licence http://commons.wikimedia.org/wiki/File:Okhotsk_Plate_map_en.png