August 25 , 2017 . EN . White Island , Piton de la Fournaise , Kilauea , Santiaguito .

Home / blog georges Vitton / August 25 , 2017 . EN . White Island , Piton de la Fournaise , Kilauea , Santiaguito .

August 25 , 2017 . EN . White Island , Piton de la Fournaise , Kilauea , Santiaguito .

August 25 , 2017 .

 

White Island , New Zealand :

Whakaari cools down
Published: Wed Aug 23 2017 1:00 PM

Declining activity has allowed the GeoNet scientists to access the active crater area for the first time since late 2015. We have been able to sample the Crater Lake and gas from the active vents.

Over the last couple of weeks we have made several trips to the volcano Whakaari (White Island). Since conditions have stabilised in the active crater we could access and sample the Crater Lake for the first time since late 2015. More excitingly, for the first time ever we have been able to sample energetic fumaroles inside the crater, including those on the lava dome that grew during the 2012 eruptions. We have also completed our repairs to the solar arrays damaged by the cyclones last autumn, and made a deformation survey.

Aerial view of White Island

On 27 April 2016 a very explosive eruption occurred from the active crater area. The eruption threw out the Crater Lake and excavated the lake floor about 13 m. The explosive blast generated by the eruption travelled across the Main Crater floor. The blast sheared off or buried survey pegs and markers we use. The tourist trails were obscured by the eruption deposits. Further mild ash eruptions followed in September 2016.
For about a year after the April 2016 eruption, water was sitting ponded in depressions and in small craters on the crater floor, however only since April this year has there been a stable lake. While we are now comfortable to call this a ‘new’ crater lake, it is quite different from past lakes. The most noticeable difference is the temperature, which last week was only 20 ˚C; in the past, a temperature of 30-70 ˚C has been typical. Our chemical analyses of a sample collected in late July, shows that the concentration of most ‘volcanic elements’ in the lake water is the lowest for 10 or even 15 years. This is because there are few volcanic gases and liquids entering the lake; this lake is mostly formed by rainfall and run-off. While the lake is now very ‘dilute’, it is still as acidic as battery acid, so you wouldn’t want to drink it or swim in it!

White Island’s new Crater Lake

In November-December 2012 a lava extrusion occurred on the active crater floor that created a small lava ‘dome’. Thermal infra-red measurements at that time indicated gases escaping the fumaroles had a temperature more than 450˚C. Following the 2016 eruptions the temperature had declined to 330˚C and has continued to decline during 2017. It is now only 114˚C, although the gas flux remains moderate and vigorous. Due to the declining activity we have been able to access and sample these. Fumarole ‘0’, a very accessible high temperature gas vent, and one that many tourists to the island visit, is also declining in temperature and is now only 152˚C down from highs over 190˚C in late 2016.

Scientists sampling gas vents on dome

We have also re-established our survey networks damaged or destroyed by the April 2016 eruption and are now establishing trends in those data. Following the 2016 eruption there was subsidence of the Main Crater floor, which has now declined or stopped. The soil gas surveys suggest little change in gas flux.
The recent observations and measurements indicate the level of volcanic unrest is declining. This reduction in activity is however creating a new opportunity for us to collect data we couldn’t before, especially about the gases in the active crater. These data, along with our more traditional data, confirm volcanic unrest is still present and Whakaari remains an active volcano.

Source : Geonet

Piton de la Fournaise , La Réunion :

Activity Report for Wednesday, August 23, 2017 at 3:00 pm (Local Time)

The eruption that began on July 14 at 00:50 local time continues. The volcanic tremor (indicator of surface eruptive intensity) is maintained at a stable and low level.

Figure 1: Evolution of the RSAM (volcanic tremor and eruption intensity indicator) between 00:00 (20h UTC) on 14th July and 15h00 (11h00 UTC) on August 23rd on the seismic station of RVL, located on the flank South of the volcano. (OVPF / IPGP)

– Two volcano-tectonic earthquakes of low magnitude were recorded under the southeast area of the enclosure during yesterday.
– No significant deformation has been observed in the last few days.

The often unfavorable meteorological conditions, as well as the observed low fluxes, have not made it possible to make reliable estimates of the flow of lava by the use of satellites.

Source : OVPF

Photo : Nicole Boube

 

Kilauea , Hawai :

19°25’16 » N 155°17’13 » W,
Summit Elevation 4091 ft (1247 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Activity Summary:
No significant change. Kīlauea Volcano continues to erupt at its summit and from the Puʻu ʻŌʻō vent on its East Rift Zone. The episode 61g lava flow is entering the ocean at Kamokuna. Surface flows are active above the pali and on the coastal plain. These flows pose no threat to nearby communities. The summit lava lake was about 43 m (140 ft) below the rim of the Overlook crater yesterday mid-morning and it rose slightly overnight. There have been no major changes in seismicity or deformation trends across the volcano.

Summit Observations:
Summit tiltmeters recorded inflation from about noon yesterday until early this morning when deflation commenced. The summit lava lake was about 43 m (140 ft) below the rim of the Overlook crater yesterday mid-morning and it rose slightly overnight. Summit tremor continues to fluctuate in response to variations in lava lake spattering, and earthquakes occurred at normal, background rates. Summit sulfur dioxide emission rates remain high.

Puʻu ʻŌʻō Observations:
Overnight, webcam images show persistent glow from long-term sources at Puʻu ʻŌʻō indicating steady activity. Seismicity is at background levels and there was no significant change in tilt overnight. The sulfur dioxide emission rate from the East Rift Zone vents remains significantly lower than the summit emission rate.

Lava Flow Observations:
The episode 61g flow is active and entering the ocean at Kamokuna. HVO observations Monday documented ongoing littoral explosions and continued slow widening of several large cracks across the active lava delta. Crack widening reflects seaward slumping of the delta’s leading edge and highlights the potential of sudden collapse into the sea. Surface lava flow activity persists on the upper portion of the flow field above the pali and on the coastal plain. On August 19, just after 4:00 am, lava emerged from a breakout about 120 m (400 ft) inland of the delta forming a spectacular cascade of lava over the seacliff and onto the western delta surface. The breakout was short lived and by early afternoon, activity had ceased.

Source : HVO

Photos : David Ford , Bruce Omori.

 

Santiaguito , Guatemala :

Type of activity: Peleana
Morphology: Complex of dacitic domes
Geographical location: 14 ° 44 ’33˝ Latitude N; 91 ° 34’13˝ W. Length.
Height: 2,500msnm.

Due to the climatic conditions and the rain that occurs in areas of the Santiaguito volcano, as of 14:30 hours the observatory of the Santiaguito OVSAN volcano and the seismic station STG3 registers the descent of a lahar moderated by the Cabello de Ángel river, Tributary of the Nimá River I. This lahar on the opposite side drags tree trunks, shrubs and sediments from the riverbeds walls where it advances, has dimensions of ~ 16 meters wide and a height of ~ 1 meter, dragging material Volcanic with blocks up to 1 meter in diameter.

Source : Insivumeh

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