In August 2018, the OVPF recorded, in the Piton de la Fournaise massif, in total:
• 36 superficial volcano-tectonic earthquakes (0 to 2 km deep) under the summit craters
• 2 deep earthquakes (> 0 km below the surface);
• 161 collapses (in the crater Dolomieu and at the ramparts of Enclos Fouqué)
Inflation of the building registered since the end of the eruption of July 13, 2018 stopped at the beginning of August. Since then, the OVPF deformation measurement networks have not recorded any significant deformation.
The deep magma recharge and pressurization of the superficial magmatic reservoir that had resumed following the end of the July 13 eruption appear to have ceased since early August.
Nevertheless, the CO2 concentrations in the far-field soil in the Plains sector (Plaine des Cafres, Plaine des Palmistes) are still high, testifying to magma always present at great depth.
It should be noted that since 2016, deep refeeding under the Piton de la Fournaise has been done by impulses, and such periods of lull in deformation and seismicity have already been observed several times in 2016 and 2017 over periods ranging from 15 at about 80 days. Given the amount of magma already present in the superficial magmatic reservoir, the next impulse of deep magma to the superficial reservoir may be the trigger for a new eruption, as was observed in 2016 or 2017. The resumption of pressurization of the magmatic reservoir had then preceded only 1 to 25 days an eruption.
Piton de La Fournaise - Illustration of the deformation over 2 months, between July 2 and September 2, 2018. Here are represented basic lines (variation of distance between two GPS receivers) crossing the building of the Piton de la Fournaise, at top (at the top), at the base of the terminal cone (in the middle) and in the far field (at the bottom). A rise is synonymous with elongation and therefore swelling of the volcano, conversely a decrease is synonymous with contraction and therefore deflation of the volcano. Any periods colored in light pink correspond to eruptions.
Sierra Negra - no thermal anomaly visible in this image Sentinel 2 bands 12-11-4 from 25.08.2018 - one click to enlarge
Due to the steady decrease in seismic energy levels, reaching even earlier values at the beginning of the eruptive period from June to August 2018 at the Sierra Negra volcano, and the decrease in the number of thermal alerts and that of SO2 emission , the IGEPN reports the possible completion of the eruptive process or the entry into a period of calm after 58 days of eruption.
Sierra Negra - Thermal Anomalies, Sulfur Dioxide Emissions and Seismicity Down at the End of August - IGEPN Doc
Two possible scenarios are proposed:
- End of Eruptive Period: This is the most possible scenario based on current surveillance data.
- Period of calm and resumption of eruption: it is possible that this period of calm is only a pause in the eruption, which can be resumed thanks to a new deep pulse of magma.
Eruptive activity occurred along five fissures on the N and NW flanks. These were characterized by the emission of lava flows covering a total area of 30.6 km2. The emission of lava flows was divided into two phases:
- the first lasted less than a day and the lava flows emitted by all the cracks (1, 2, 3, 4 and 5) covered an area greater than 17 km2
- and the second, including the emission of lava flows lasted 57 days and focused on crack 4 covering an area of approximately 13 km2. The lava flows resulting from this crack reached the sea on July 6 and modified the coastline of the island, increasing the territory by 1.5 km2.
Sierra Negra - map of the flows and fissures of the June-August 2018 eruption - Doc. IGEPN / 01.09.2018
At Merapi, lava extrusion continues at the summit; the dome reached 1 September an estimated volume of 62,500 m³.
Dome growth in height increases the risk of instability and collapse, which could cause pyroclastic flows
Seismicity remains low and soil deformation is negligible at the top of Kīlauea.
An unmanned aircraft systems team recently toured the edge of the crater, which is now seven times larger than before the eruption. Overflight data will be used for digital elevation models that document changes at the top.
From early May 2018 to the present day, the volume change at the peak exceeds 825 million cubic meters, or 1 billion cubic meters. The vertical collapse of the crater is over 487 meters.
The Hawaii Volcanoes National Park is still closed, but the Superintendent has set a goal of reopening some closed areas by September 22.
A geomorphology team from the National Parks Service has begun to assess the stability of areas damaged or potentially damaged by earthquakes. The results will determine where visitors can go safely.
As of August 29, 32 park buildings have been inspected for earthquake damage. The geomorphology team has also performed an initial inspection of the Thurston Lava Tube, but additional assessments are needed to determine if the lava tunnel can be reopened safely.
Source: Big Island video news