The Alaska Volcano Observatory has raised the alert level of Semisopochnoi in the Aleutian volcani arc, to Advisory and the aviation code to Yellow this July 5 at 6:51, following an increase in seismicity.
No explosive activity has been recorded by the Arak infrasonic network, and satellite observation is disturbed by cloud cover.
Semisopochnoi is the largest young volcanic island in the western Aleutians and consists of a variety of volcanic landforms.
The basaltic pyroclastic materials built a shield about 20 km wide at sea level, which resulted in a post-glacial eruption of pumice and ashes of dacite and andesite, producing an 8 km wide caldera . The small composite cones are both pre- and postglacial. Mount Cerberus is the most active of the three youngest cones in the caldera. A historic eruption of Semisopochnoi was reported in 1873 and at least four others may have occurred in the last hundred years, but the documentation is insufficient. These eruptions apparently emanate from the flanks of Mount Cerberus; the most recent flow seems to be less than a century old.
Stromboli - top zone - photo by s. Branca (INGV) in the morning of July 4 and the afternoon of July 5, 2019, the helicopter of the 2 nd air core of the Coast Guard of Catania. - Doc. INGV
The National Institute of Geophysics and Volcanology, Observatory Etnéen, communicates that between 14:40 h and 15:30 h this July 5, thanks to the helicopter made available by the 2nd nucleus of the coast guards of Catania, they have observed that the eruptive activity at the two active mouths in the south-central crateric area of Stromboli has changed from the intense spattering described in the previous release, to an intense Strombolian activity. The explosions reach heights up to 150 m with products that occasionally settle on the Sciara del Fuoco, generating rolling of blocks along the slope that reaches the coastline.
It remains in the northern zone of the crateric terrace a sporadic explosive activity. In addition, during the overflight, it was found that the effusive activity stopped and that the lava overflow of the south-central crater zone and its lava flows in the Sciara del Fuoco are no longer supplied, and therefore in cooling .
Stromboli - the top zone taken by s. Branca (INGV) in the morning of July 4 and the afternoon of July 5, 2019, the helicopter of the 2 nd air core of the Coast Guard of Catania. - Doc. INGV
Stromboli - 04.07.2019 / morning - the crater terrace after the paroxysm of July 3rd - video S. Branca / INGV
Regarding submarine volcanism off Mayotte, the SHOM, a public operator for maritime and coastal geographical information, has posted images before and after the observation of an eruption.
Taken in 2014, and the 1st of July 2019 by the Beautemps-Beaupré, it shows the existence of a relief up to 800 meters by 5 km wide, with a high point at 2568m on a medium bottom around 3300m.
Source: SHOM / Twitter