The persistent centuries-long eruption at Yasur continued between February and July 2018. According to the Vanuatu Meteorology and Geo-Hazards Department (VMGD), activity consists of ongoing explosions, some of which are strong. The activity is confined to the crater.

Based on visual observations and satellite data, VMGD reported on 19 March 2018 that explosions remained strong. Using information from webcam images, satellite data, model data, and local visual observations, the Wellington Volcanic Ash Advisory Centre (VAAC) reported that during 5-6 June, 14-15 June, 17-18 June, and 20-21 June, intermittent, low-level ash plumes rose to altitudes of 0.9-1.5 km and drifted in various directions. During the 5-6 June episode, ash was not identified on satellite imagery.

Satellite imagery during clear weather on 25 June showed two distinct heat sources in the crater and a diffuse gas plume blowing NW (figure 49). VMGD reported some stronger explosions during 27-28 June. Based on webcam images the Wellington VAAC reported that on 29 June intermittent, low-level ash plumes rose to an altitude of 1.8 km and drifted NW.

Figure 49. Sentinel-2 satellite images of Yasur on 25 June 2018. The top image uses the Atmospheric Penetration filter, which clearly shows two closely spaced hotspots in the crater. The bottom natural color image (with minor color adjustments) shows a thin, faint plume emanating from the crater and blowing NW. Courtesy of Sentinel Hub.

The Alert Level remained at 2 (on a scale of 0-4) throughout the reporting period. VMGD reminded residents and tourists that hazardous areas were near and around the volcanic crater, within a 395-m-radius permanent exclusion zone (shown in figure 48 of BGVN 43:02), and that volcanic ash and gas could reach areas impacted by trade winds.

During the reporting period, MODIS satellite instruments using the MODVOLC algorithm recorded thermal anomalies between 4 and 16 days per month, many of which had multiple pixels. May 2018 had the greatest number of days with hotspots (16), while the lowest number was recorded during April (4). The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, recorded numerous hotspots every month during the reporting period. Almost all recorded MIROVA anomalies were within 3 km of the volcano and of low or moderate radiative power.

Geological Summary. Yasur has exhibited essentially continuous Strombolian and Vulcanian activity at least since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island in Vanuatu, this pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide open feature associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department, Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://www.metservice.com/vaac, http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).