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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #Actualités volcaniques

At Piton de La Fournaise, the eruption continues, but the volcanic tremor (indicator of surface eruptive intensity) continues to decline very gradually.
The decline in the eruptive tremor is reflected on the ground by a decline in activity. During an overflight carried out on 2 August by the OVPF, no projection was visible at the level of the eruptive cone. The main mouth, active these days, is now completely clogged. The second mouth, of smaller size, showed an extremely low level of magma with strong degassing.
At 10.30 am (local time), only a few lava arms were visible on the surface, the nearest being 520 meters from the eruptive cone, with the rest of the activity occurring in the lava tube.

Piton de La Fournaise - Evolution of RSAM (volcanic tremor and eruption intensity indicator) between 00h00 (20h UTC) on 14th July and 15h30 (11h30 UTC) on 3rd August on the seismic station of RVL, located on The southern flank of the volcano. (© OVPF / IPGP)

Piton de La Fournaise - Evolution of RSAM (volcanic tremor and eruption intensity indicator) between 00h00 (20h UTC) on 14th July and 15h30 (11h30 UTC) on 3rd August on the seismic station of RVL, located on The southern flank of the volcano. (© OVPF / IPGP)

Piton de La Fournaise - Shooting of the eruptive site on 02/08/2017 at 10h30, local time. (© OVPF / IPGP)

Piton de La Fournaise - Shooting of the eruptive site on 02/08/2017 at 10h30, local time. (© OVPF / IPGP)

Piton de La Fournaise - 02.08.2017 - tunnels and lava flows at 10:30 am local time. (© OVPF-IPGP)

Piton de La Fournaise - 02.08.2017 - tunnels and lava flows at 10:30 am local time. (© OVPF-IPGP)

At the level of the resurgences of lava, also called "ephemeral mouths", morphologies and phenomena characteristic of the flows in tunnels were observed (numbers 1 to 8 in the picture above):
1) Under the pressure of the lava circulating in the tunnel (overpressure linked to an increase in flow or a "plug downstream") a hornito was built. The latter was no longer active during the observations of this morning.
2) In the axis of the hornito and in the middle of a pahoehoe lava field, a very channeled effluent of lava 20 meters long and 1 m wide shows that the tunnel was still active and a place of lava flows.
3) Two ephemeral mouths had recently opened at the roof of the tunnel just before the shot.
4-5-6) The longest flow observed this morning, was 220 m long, and was initiated by an ephemeral mouth located in the alignment of the points described previously. At the point where the free surface was the widest, the flow reached barely 10 meters (in 4); More downstream and definitely linked to a lower slope, the casting spread out with a texture on a leaf / aa (at 5) to its front (at 6). It should be noted that even if the surface at 5 and 6 were cooled, the core of the casting was always liquid as evidenced by the two red lobes visible on both sides of the front.
7-8) Two other tongues of lava from ephemeral mouths at 520 meters from the vent were visible. The extension of these two flows was limited, with a length of 50 and 180 m.


In the field, no projection is visible. Most of the activity is now done in lava tunnels with some visible surface resurgences on low spatial extension.
No earthquakes have been recorded in the past 24 hours.
The trend recorded on deformation sensors, particularly GPS, at the top of the volcano, seems to be again showing a recovery in inflation. This parameter will be followed in the next few days.

Estimates carried out using satellite methods via the HOTVOLC platform (OPGC - Clermont Ferrand) show a minimum flow rate of less than 1 m3 / s.
The total volume of lava emitted to date is estimated at 7.2 ± 2.4 Mm3 (MIROVA).


Source: OVPF

Sinabung - morphological changes of the lava dome - 03.08.2017 / 13h23 - photo Endro Lewa

Sinabung - morphological changes of the lava dome - 03.08.2017 / 13h23 - photo Endro Lewa

In Sinabung, two pyroclastic flows are reported on 4 August at 11:22 and 11:35 WIB, respectively, and 4,500 meters long to the south-east, accompanied by a co-pyroclastic cloud rising in the fog, and 3,000 meters to the East.
The top lava dome changed its morphology.


Source: Magma - VSI

 Sinabung - pyroclastic flow of the 04.08.2017 / 11h22 WIB - photo magma VSI / Edward Pandia

 Sinabung - pyroclastic flow of the 04.08.2017 / 11h22 WIB - photo magma VSI / Edward Pandia

A video by Thierry Dockx (LAVE-Belgium) and Tanguy de Saint-Cyr details an explosive event in the Santiago crater of Masaya on feb.2016. It seems that this episode released the existing tension on the crust covering part of the Lava lake which has seen its agitation diminish.


In August 2017, the volcano was still degassing abundantly.


Sources: Adventure and Volcanoes - Evgenia Ilynskaya / Twitter

Video: Thierry Dos / Tanguy de Saint-Cyr / Adventure and volcanoes

Masaya - degassage important this 03.08.2017 - photo Evgenia Ilynskaya / Twitter

Masaya - degassage important this 03.08.2017 - photo Evgenia Ilynskaya / Twitter

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