Tonga’s volcano eruption and tsunami explained in maps and charts – Al Jazeera English

There are some 1,350 potentially active volcanoes around the world, many located around the Pacific ‘Ring of Fire’.
The South Pacific nation of Tonga is still cut off from the world two days after an underwater volcano erupted –  triggering tsunami alerts across the Pacific.
Tonga comprises 169 islands, of which 36 are inhabited, and has a population of about 105,000 people.
As of Tuesday, Tonga police had reported two deaths, but the true extent of casualties is still not clear with most communication lines still down.
On January 15, the Hunga Tonga–Hunga Haʻapai volcano, about 70km (45 miles) northwest of the nation’s capital, Nuku’alofa, sent plumes of smoke 20km (12 miles) into the air and caused significant damage.
Before and after satellite images show smoke rising from the underwater volcano days before it erupted.
While the volcano has erupted regularly over the past few years, there has been nothing like this most recent eruption. Early data suggests it was the biggest eruption since Mount Pinatubo in the Philippines more than 30 years ago.
Robin George Andrews, a science journalist, volcanologist and author of Super Volcanoes, told Al Jazeera from London that “it was the most energetic [volcanic] explosions in the entire 21st century”.
Map showing where Hunga-Tonga-Hunga-Haapai is
There are some 1,350 potentially active volcanoes around the world,  according to the US Geological Survey.
Many are located along a 40,000km (25,000-mile) arc along the Pacific known as the “Ring of Fire”, which is also where about 90 percent of all earthquakes occur.
Tonga is home to several volcanoes, all along the Ring of Fire.
Map showing where the world's underwater volcanoes are
There are about one million undersea volcanoes – and most are extinct. According to the Global Foundation for Ocean Exploration group, about “three-quarters of all volcanic activity on Earth actually occurs underwater”.
During an eruption, hot magma forces the oceanic crust open. This can lead to tsunamis – a series of ocean waves caused by the displacement of water.
Infographic showing how volcanoes erupt
A 1.2-metre (4 foot) wave swept ashore in the Tongan capital, with locals reporting fleeing to higher ground, leaving behind flooded houses, some with structural damage, as rubble and ash fell from the sky.
Tsunami warnings were issued across the Pacific, including in Samoa, Australia, Japan, Hawaii, Chile and the US Pacific coast.
Waves damaged boats as far away as New Zealand and Santa Cruz, California – more 8,500km (5,300 miles) away – but did not appear to cause any widespread damage.
By Sunday, the warnings had receded.
Map showing Tonga's tsunami warnings
Satel­lite im­ages showed a plume of ash, steam and gas ris­ing like a mush­room above the Pa­cif­ic wa­ters.
A vol­canic erup­tion and tsuna­mi sev­ered com­mu­ni­ca­tions with Ton­ga, leav­ing the Pa­cif­ic king­dom iso­lat­ed.
Of­fi­cial says there is an im­me­di­ate need for drink­ing wa­ter and food, as ef­forts be­gin to as­sess scale of dam­age.
The erup­tion of Hun­ga-Ton­ga-Hun­ga-Ha’apai trig­gered tsuna­mi waves in Ton­ga and oth­er places around the world.
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