Tonga Volcanic Eruptions, Tsunami in many countries
- The massive underwater volcanic eruption in Tonga was so powerful it was recorded around the world.
- It triggered a tsunami that flooded Pacific coastlines from Japan to the United States, scientists said Sunday.
About the Context
- Dramatic satellite images showed the long, rumbling eruption of the Hunga Tonga-Hunga Ha'apai volcano spew smoke and ash in the air, With a thunderous roar heard 10,000 kilometres (6,000 miles) away in Alaska.
- The US Geological Survey recorded Saturday's eruption as equivalent to a 5.8 magnitude earthquake at zero depth.
- But the full extent of the damage in Tonga was unclear Sunday with communication lines down.
- A 1.2 metre (four-foot) wave swept ashore in the Tongan capital Nuku'alofa with locals reporting they had fled to higher ground, leaving behind flooded houses, some with structural damage, and with small stones and ash falling from the sky.
Warning in multiple countries
- The US and Japan have advised people on their Pacific coastlines to get away from the shore as a precaution against tsunami waves caused by a volcano eruption in the South Pacific.
- Japan has warned of waves as high as three metres, and waves of 1.2 metres hit the south of the country.
- The US warned of strong currents and waves, and coastal flooding.
- In New Zealand, more than 2,300 kilometres from Tonga, 120 people were evacuated from northern coastal areas and several boats destroyed when a huge wave crashed into a marina.
- Australia's popular Bondi Beach in Sydney was briefly evacuated as a precaution while in California, coastal streets in Santa Cruz were awash and closed to traffic.
Eruption in HUNGA-TONGA-HUNGA-HA'APAI Volcano
- The volcano consists of two small uninhabited islands, Hunga-Ha'apai and Hunga-Tonga, poking about 100m above sea level 65km north of Tonga's capital Nuku'alofa.
- But hiding below the waves is a massive volcano, around 1800m high and 20 kilometres wide.
- The Hunga-Tonga-Hunga-Ha'apai volcano has erupted regularly over the past few decades.
- During events in 2009 and 2014/15 hot jets of magma and steam exploded through the waves. But these eruptions were small, dwarfed in scale by the January 2022 events.
- But this is one of the massive explosions the volcano is capable of producing roughly every thousand years.
About Volcanic eruptions underwater
- Submarine volcanic eruptions are characteristic of the rift zones where crustal plates are being formed.
- These rift zones, which are found in all of the Earth's major ocean basins, are known as seafloor spreading centers because they are places where tectonic plates are moving away from each other.
- Most seafloor spreading centers lie at depths exceeding 2,000 meters (1.2, miles) and, as a consequence, approximately three-quarters of all volcanic activity on Earth occurs as deep, underwater eruptions.
- Spreading center eruptions typically produce a rock called basalt, which is the principal rock that makes up oceanic crust.
- Although these eruptions can be locally violent, the style of eruptions can result in the deformation of the Earth's crust, closely resembling the eruptions of Hawaiian volcanoes.
- We're still in the middle of this major eruptive sequence and many aspects remain unclear, partly because the island is currently obscured by ash clouds.
- The latest eruption has stepped up the scale in terms of violence.
- The ash plume is already about 20km high.