How underwater volcanoes are born

There was an underwater volcano eruption on January 18th, near Tonga in the Pacific ocean. It was the biggest recorded anywhere on the planet in more than 30 years. Tonga’s volcanic eruption generated tsunami waves of up to 15 meters (close to 50 feet). 

By Siloé Bonnet and Marcel Duffy – 6th grade.

Credit: NOAA

Three individuals were killed and hundreds of dwellings in Tonga’s smaller islands were destroyed as a result of the massive eruption. Dramatic photographs from space showed the eruption in real time, as a massive plume of ash, gas, and steam blasted into the skies, sending tsunami waves cascading across the Pacific. People were seen running as waves overwhelmed Tonga’s capital, Nuku’alofa, as the afternoon sky turned pitch black owing to the heavy ash cloud, according to footage shared on social media. Tsunami waves were also detected thousands of miles away, on the West Coast of the United States, in Peru, New Zealand, and Japan. At least two persons have died in Peru after being swept away by powerful seas. There have been two deaths reported.

“This volcanic activity is to be linked to that of the “Pacific Ring of Fire”, where the Pacific Ocean sinks by subduction under a continent (case of the Andes Cordillera) or under another sector of the Pacific such as at the level of the Tonga.”, explained Ms. Bamouh, LILA middle school science teacher. “The lava and ash emitted by these Tongan volcanoes are mainly andesitic (a lava called andesite with 60% silica and very common in subduction zones such as the Andes).” says Ms.Bamouh. “The eruptions that built this new volcano were of the phreatomagmatic type (also called surtseyan). The seabed was made up of ash and other porous rocks soaked in seawater (groundwater)” she explained. “The arrival of very hot magma in this groundwater table boiled the water, which had difficulty escaping. The pressure increased and this generated relatively “moderate” explosions (like a pressure cooker whose valve would be clogged. A more or less continuous arrival of magma led to a series of explosions which followed one another.” according to Ms. Bamouh.

During the pandemic, Tonga has only recorded one coronavirus case, and there is concern that relief workers may bring the virus with them from countries where the Omicron variety is growing quickly. On January 24, 2022, two New Zealand navy ships arrived in Tonga with essential water supplies for the Pacific island nation still reeling from a volcano eruption and tsunami and cut off from the rest of the globe. Damage of a crucial underwater cable stopped international and inter-island connections, significantly limiting Tonga’s communication facilities. While rescue teams struggle to salvage the underwater cable, many Tongans living outside the nation face a long wait to reunite with loved ones back home.

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