Amy Debattista, The Lord Howe Island Signal

At 3:10pm AEDT on Saturday 15 January 2022 the Hunga Tonga-Hunga Ha’apai volcano (near Tonga) erupted with a blast so powerful that it caused a shock wave that was heard on Lord Howe Island that evening and reached the other side of the planet. A 7 hectopascal change in the barometric pressure was recorded at Lord Howe Island Met Station as the shockwave passed over the island.

The blast triggered several Tsunami waves and spewed a column of volcanic ash more than 30 kilometres up into the air. The sea level gauge at Nuku’alofa, Tonga recorded a Tsunami wave of 1.19 metres before it stopped reporting. Tsunami waves were also observed at other sea level gauges across the South Pacific. The waves that subsequently arrived at the Australian coast were comparable to some of the biggest tsunami waves recorded here, including those generated by the southern Chile earthquake in 1960 – one of the largest on record.

At 8:00pm AEDT on Saturday the Bureau of Meteorology issued a Tsunami Warning for the Marine Environment at Lord Howe Island. While evacuations are not necessary for a Marine Threat Warning, people in these areas are advised to get out of the water and move away from the immediate water’s edge. Tsunami waves are more powerful than the same size beach waves. There will be many waves and the first wave may not be the largest. Marine Threat Tsunami Warnings were also issued for Norfolk Island, Macquarie Island, the NSW Coast and parts of the QLD, VIC & TAS coasts.

At 9:18pm AEDT the Bureau upgraded the Marine Warning to a Land Threat Warning for Lord Howe Island and Norfolk Island. An evacuation order was issued for low-lying areas of Lord Howe Island. Approximately 50-100 people were evacuated, with assistance from the SES, Police and LHI Board, to the Old Met Site and the Golf Club for those that live down south.

Tsunami waves of up to 1.10 metres were observed at Lord Howe Island during Saturday night and Sunday morning. Some of the other locations that recorded waves were 1.27 metres at Norfolk Island, 1.18 metres at Vanuatu, 1.14 metres at New Zealand, 82cm at the Gold Coast, 65cm at Port Kembla, 77cm at Eden’s Twofold Bay, 50cm at Hobart, 43cm at Coffs Harbour and 16cm at Esperance.

At 10:10am AEDT on Sunday 16 January the Land Threat Warning for Lord Howe Island was downgraded to a Marine Threat. All beaches around the island remained closed until the Marine Threat was cancelled at 7:56pm on Sunday. Some beach erosion and broken coral was observed as a result from the Tsunami waves in the days after the event.

This article appeared in The Lord Howe Island Signal, 29 January 2022.