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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 : #Nouvelle brève

Volcanic emissions are a critical pathway in the Earth's carbon cycle.

Inter-university research in applied science and engineering shows that aerial measurements of volcanic gases using UAS / unoccupied aerial systems transform our ability to measure and monitor plumes from a distance and limit global volatile fluxes from volcanoes.

Aerial sightings of Manam, Papua New Guinea. (A) Regional tectonic framework. Manam is located in the volcanic arc of West Bismarck (yellow star). (B) The more energetic, high-altitude plume from the southern crater often dispersed in a different direction than the lower low-level emissions from the main crater. Image taken on May 25, 2019. (C) An image of the nadir acquired during a UAS flyby on May 22, 2019 showed magma to be present at shallow levels in the southern crater. A strong plume emanated from the crater. (D) View of the UAS during the approach to the plume. The floating plume from the south crater rose to about 2-3 km above sea level before dispersing laterally. (E) Aerial view of the summit showing passive degassing

Aerial sightings of Manam, Papua New Guinea. (A) Regional tectonic framework. Manam is located in the volcanic arc of West Bismarck (yellow star). (B) The more energetic, high-altitude plume from the southern crater often dispersed in a different direction than the lower low-level emissions from the main crater. Image taken on May 25, 2019. (C) An image of the nadir acquired during a UAS flyby on May 22, 2019 showed magma to be present at shallow levels in the southern crater. A strong plume emanated from the crater. (D) View of the UAS during the approach to the plume. The floating plume from the south crater rose to about 2-3 km above sea level before dispersing laterally. (E) Aerial view of the summit showing passive degassing

By combining multi-scale measurements from ground-based remote sensing, long-range aerial sampling and satellites, the study presents complete gas flows - 3760 ± [600, 310] tonnes per day of CO2 and 5150 ± [730 , 340] tonnes per day of SO2 - for a major source of volcanic emission on a global scale as yet unknown: Manam, Papua New Guinea.

Manam - View from UAS during plume approach. The floating plume from the south crater rose to about 2-3 km above sea level before dispersing laterally - photo K. Wood 05.2019

Manam - View from UAS during plume approach. The floating plume from the south crater rose to about 2-3 km above sea level before dispersing laterally - photo K. Wood 05.2019

Manam - during the flyby on May 22, 2019, magma was present at shallow levels in the southern crater. and a strong plume emanated from the crater. - photo K. Wood

Manam - during the flyby on May 22, 2019, magma was present at shallow levels in the southern crater. and a strong plume emanated from the crater. - photo K. Wood

Manam - hot spot and emission of bluish gases - Sentinel-2 L1C image bands 12,11,4 / 20.05.2019 - one click to enlarge

Manam - hot spot and emission of bluish gases - Sentinel-2 L1C image bands 12,11,4 / 20.05.2019 - one click to enlarge

Previous satellite measurements of Manam's SO2 emissions between 2005 and 2015 indicate an average SO2 flux of 1480 ± 750 tonnes per day. However, despite a history of persistent passive degassing, frequent explosive activity and globally significant SO2 emissions, there are no constraints prior to carbon degassing at Manam from in situ measurements.

A major eruption on August 25, 2018 from the south crater generated a 15 km high eruption column and triggered lava flows from the main crater into the northeast avalanche valley, which continued until October 12, 2018. This eruption marked the start of a new phase of high activity after a period of relative rest since previous Strombolian eruptions in early 2017.

Other moderate to large explosive eruptions occurred on September 30, 2018, December 8, 2018, January 8 and 24, 2019, June 28, 2019 and, more recently, November 6, 2019. The inter-eruptive periods were characterized by degassing persistent, strong and passive.

Manam - equipment of the drone for multigas measurements - photo E.Liu 05.2019

Manam - equipment of the drone for multigas measurements - photo E.Liu 05.2019

The CO2 / ST ratio of 1.07 ± 0.06 suggests a modest contribution of tectonic plate sediments to the sub-arc mantle.
The study finds that aerial strategies reduce the uncertainties associated with ground-based remote sensing of SO2 flux and allow near real-time measurements of plume chemistry and carbon isotopic composition.

The data underscore the need to take into account the time average of the time variability of volcanic gas emissions in the estimates of global flows.

 

Sources:

- Advances Science Mag - Aerial strategies advance volcanic gas measurements at inaccessible, strongly degassing volcanoes. - E.J. Liu & al.

https://advances.sciencemag.org/content/6/44/eabb9103

- Sentinel Hub personal archives

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