Tonga undersea eruption illustrates cascading risks scenario, says UN-ESCAP

Vinson Kurian | | Updated on: Feb 07, 2022
The eruption of an underwater volcano off Tonga, which triggered a tsunami warning for several South Pacific island nations, is seen in an image from the NOAA GOES-West satellite

The eruption of an underwater volcano off Tonga, which triggered a tsunami warning for several South Pacific island nations, is seen in an image from the NOAA GOES-West satellite | Photo Credit: CIRA/NOAA

‘Earth observation satellites alone can collect data, develop scenarios’

The January-14 eruption of the undersea volcano in Tonga is illustrative of a cascading risks scenario where one disaster triggers another, exposing and exacerbating multiple critical vulnerabilities in small island developing states (SIDS). 

For a cascading risk of this magnitude on a tiny island in the vast South Pacific basin, earth observation satellites are the only means to collect data and develop scenarios, notes Dr Sanjay Srivastava, Chief, Disaster Risk Reduction, UN-ESCAP, Bangkok.

Unlike anything seen before

The Himawari-8 satellite showed the rapid expansion of a volcanic cloud following the explosive eruption. It captured an abrupt shock wave that propagated radially outward in all directions. 

The Geostationary Operational Environmental Satellite-17 captured the images of a vast plume of material that created what volcanologists call an ‘umbrella cloud’. 

Powerful waves ringing through the atmosphere after the eruption were unlike anything ever seen before as satellite data showed that the volcano provoked an unusual pattern of atmospheric gravity waves, Srivastava wrote to BusinessLine.

Early warning systems

The magma is under enormous pressure from gases trapped within. A fracture in the rock allows gases to expand and blast it, releasing huge energy through eruption. The understanding of this scientific background resulted in the development of volcano early warning systems, Srivastava said. 

Field reports highlight that at-risk communities in Tonga were warned about the increased activity at the volcano a day before the eruption and also about the incredibly loud bang when it erupted. These warnings allowed many people to scramble to higher grounds in time.

Recent advances in geospatial and earth observation systems in conjunction with drones, connected devices data, internet of things (IoT) and social media have been extensively used for impact assessment of the Tonga volcano eruption and tsunami. 

Impact assessment using tech

Enabled through cloud computing and big data analytics techniques, these technologies provided near real-time impact mapping and risk visualisation, Srivastava explained. 

“For instance, Maxar Technologies used artificial intelligence to integrate satellite imagery and data with other forms of data such as social media sentinel data or drone footage. It enabled them capture in real time the eruption, with the plume of ash, steam and gas rising like a giant mushroom above the South Pacific.” 

ESCAP had contacted space-faring countries of its Regional Space Applications Programme for satellite imagery while the UN Satellite Centre activated its Emergency Mapping service. 

“The real and near real-time impact mapping helped more effective and targeted emergency responses and guided the post-disaster recovery and reconstruction,” Srivastava said.

Adaptation priorities 

Adaptation priorities for Tonga include protecting mangroves, improving dryland crop production, resilient water resource management as well as strengthening early warning systems and resilient infrastructure, the top UN-ESCAP official said.

Ground reports highlight that reefs, lagoons and other natural features have protected parts of Tonga, while amplifying the waves in certain areas. International and regional cooperation in science-based risk assessment and early warning, as seen in case of the Tonga eruption, is a welcome trend. 

Resilient infrastructure 

Early warning systems can be well complemented by nature-based solutions. Rresilient ICT infrastructure is a crucial need for addressing the Pacific’s critical vulnerability. Here, the ESCAP initiative on e-resilience can help address the vulnerability of ICT systems. 

The launch of the Infrastructure for Resilient Island States (IRIS) initiative at COP 26 in November 2021, in the presence of Heads of Governments from Australia, Fiji, India, Jamaica, Mauritius and the UK, signals an encouraging trend to facilitate building resilience in the region, Srivastava said.

Published on February 07, 2022
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