Honiara (Commonwealth Union)_An earthquake slammed West Java, Indonesia, on Monday, triggering a series of catastrophic landslides that killed more than 270 people, with at least 40 more still missing under the mud, rubble, and debris.
A day later, 5000 kilometres distant, the Solomon Islands were struck by two earthquakes, the first of which had a magnitude of 7.0 and damaged buildings, brought down the roof of Australia’s High Commission in Honiara, and triggered first tsunami fears. This occurred just hours after a magnitude 3.2 earthquake devastated renowned NSW tourist destination Batemans Bay, and only a month after a similar incident rocked the little town of Mansfield in Victoria.
The US Geological Survey detected 19 seismic events among Australia’s island neighbours on November 22 alone. The bulk were aftershocks on the still trembling Solomon Islands, but there was also a 5.0 magnitude quake south of Fiji and another 4.7 magnitude incident off the coast of Indonesia. So, what precisely is causing what appears to be a rash of earthquakes in our region right now? And why is Indonesia’s 5.6 magnitude earthquake having such catastrophic consequences yet a much greater event days later near the Solomon Islands has yet to claim a single life? Moreover, why has Australia, a vast island, mainly avoided the tectonic agony that has shook its neighbours such as Indonesia and New Zealand?
To understand what causes earthquakes and volcanoes, we must first examine the tectonic plates, which are vast, unevenly formed slabs of rock that make up the majority of the Earth’s crust. According to CNN, the huge amounts of heat stored in the planet’s centre constantly raise these plates over the mantle – a layer of solid and molten rock beneath the Earth’s crust.
Now, island nations such as the Solomon Islands, Indonesia, New Zealand, and Vanuatu are located on the west and southwest rims of the Ring of Fire, a 40,000km arc stretching from the Pacific Plate’s edge to smaller tectonic plates such as the Philippine Sea Plate and other plates that line the Pacific Ocean’s edge.
“The boundary of the tectonic plates goes across New Zealand, Fiji, the Solomon Islands… all the way up to Japan, via the west coast of the United States, and down to South America,” Geoscience Australia senior duty seismologist Taja Pejic explained. “That’s the Pacific Ring of Fire.”
It got its name because it is home to 90% of the world’s seismic activity around the boundaries of the major plates. It also has 75% of the world’s active volcanoes, including Tonga’s Hunga Tonga-Hunga Ha’apai volcano, which erupted with the greatest recorded eruption in January this year.
Volcanoes along the Ring of Fire are frequently generated when one plate is forced beneath another into the mantle by a process known as subduction. It also implies that major earthquakes, which have the potential to cause tsunamis, occur in these subduction zones.
