<![CDATA[Explained: Asia's deadliest eruptions - and four volcanoes to watch]>

Predicting when a volcano might erupt is notoriously difficult, and if the prediction is wrong the consequences can be devastating " as seen with the explosion on New Zealand's White Island on Monday that claimed up to 16 lives and left dozens seriously injured.

Scientists are able to monitor emissions of gases, the shape of the volcano itself and whether there has been any recent earthquakes to gauge how likely an eruption might be.

But anticipating whether such signals indicate an imminent eruption, or one that's weeks, months or even years away, depends entirely upon the individual volcano " and sometimes the increase in activity is so sudden that no warning can be given or alarm raised.

There are thousands of active and dormant volcanoes that encircle the Pacific Ocean " often referred to as the "Ring of Fire". Most lie far from major cities and are watched carefully for signs of danger, but some are much closer to population centres. In Indonesia, for example, an estimated 8.6 million people live within 10 kilometres of a volcano.

A map showing the 'Ring of Fire' in the Pacific Ocean. Image: United States Geological Survey alt=A map showing the 'Ring of Fire' in the Pacific Ocean. Image: United States Geological Survey

Here, we list seven of the region's biggest and most recent notable eruptions " and four volcanoes to watch ...

Anak Krakatoa erupts volcanic ash and steam over the waters of Indonesia's Sunda Strait, on September 22, 2018. Photo: EPA alt=Anak Krakatoa erupts volcanic ash and steam over the waters of Indonesia's Sunda Strait, on September 22, 2018. Photo: EPA

Anak Krakatoa, Indonesia " an eruption on December 22, 2018, triggered a tsunami that killed more than 420 people and displaced 40,000. The volcano, whose name means "Child of Krakatoa", grew from the remains of Krakatoa, whose eruption in 1883 caused tens of thousands of deaths and triggered a period of global cooling.

Ash and lava spews from Mount Mayon in the Philippines, January 2018. Photo: EPA alt=Ash and lava spews from Mount Mayon in the Philippines, January 2018. Photo: EPA

Mayon, the Philippines " erupted for several weeks in January 2018, belching red-hot lava fountains and huge columns of ash and lava into the sky in the latest of dozens of eruptions over the past 500 years. The explosion in 1991 of Mount Pinatubo, also in the Philippines, was one of the 20th century's biggest, killing about 800 people.

A handout aerial picture shows the eruption in September 2014 of Mount Ontake, between Gifu and Nagano prefectures, Japan. Photo: EPA alt=A handout aerial picture shows the eruption in September 2014 of Mount Ontake, between Gifu and Nagano prefectures, Japan. Photo: EPA

Ontake, central Japan " erupted unexpectedly in 2014, killing 47 people who were caught off guard while resting after climbing the peak. Most were killed by flying rocks. Survivors battled hot air and ash, rocks and debris as they fled the mountain. Seismologists in Japan said there had been no warning of such a big eruption.

An aerial view of the pyroclastic flows and lahar deposits left behind by the eruption of Mount Unzen in 1991. Photo: United States Geological Survey alt=An aerial view of the pyroclastic flows and lahar deposits left behind by the eruption of Mount Unzen in 1991. Photo: United States Geological Survey

Unzen, southern Japan " exploded in 1991. Most of the 43 people who died were killed by pyroclastic flows of hot ash and steam that raced down the mountainside. An earlier eruption, in 1792, killed an estimated 15,000 people.

Tambora, Indonesia " exploded in 1815 in the biggest known eruption in 1,000 years, one so powerful it, too, altered global weather. About 92,000 people are thought to have died from the eruptions, including 82,000 who perished of starvation and disease and 10,000 killed by its direct impact.

Ones to watch:

A plume of ash is released as Mount Agung volcano erupts on May 31, 2019. Photo: AFP alt=A plume of ash is released as Mount Agung volcano erupts on May 31, 2019. Photo: AFP

Agung, Bali (Indonesia) " After a series of eruptions in 1963 that claimed about 1,900 lives, Agung remained relatively quiet until the latter half of 2017, when the popular Indonesian resort island began experiencing volcanic earthquakes " reaching a crescendo of more than 1,000 per day at its peak. Eruptions soon followed, forcing the evacuation of 40,000 people and surrounding airports to close. The most recent eruption was recorded in June this year.

Lava flow and ash clouds are seen emanating from Mount Sinabung in April 2015. Photo: Xinhua alt=Lava flow and ash clouds are seen emanating from Mount Sinabung in April 2015. Photo: Xinhua

Sinabung, Sumatra (Indonesia) " Sinabung volcano awoke in 2010 after a 400-year sleep, and is currently one of the most active volcanoes in Indonesia. It has been pretty much in constant eruption since September 2013, and there are still frequent volcanic earthquakes.

Kadovar volcano erupting in January 2018. Photo: Facebook / Brandon Buser alt=Kadovar volcano erupting in January 2018. Photo: Facebook / Brandon Buser

Kadovar, Papua New Guinea " a relatively unknown 365-metre-high volcanic island that had no confirmed eruptions before 2018, when it belched a 2,100-metre plume of ash into the sky, forcing all the island's inhabitants to be evacuated. Activity of some form had previously been reported in 1976 and 1981. Identified volcanic risks at Kadovar include further potential explosive activity, landslides, and resulting possible tsunami.

A still from a video shows an eruption near Mount Kusatsu-Shirane in Japan's Gunma prefecture on January 23, 2018. Photo: EPA alt=A still from a video shows an eruption near Mount Kusatsu-Shirane in Japan's Gunma prefecture on January 23, 2018. Photo: EPA

Kusatsu-Shirane, Japan " a minor eruption on January 23 last year killed a member of the armed forces who was skiing nearby and injured several other after triggering an avalanche. The volcano's summit has now been declared off limits to the public. According to Japan's Meteorological Agency there had been no volcanic activity at the site of the eruption for about 3,000 years.

Additional reporting by Associated Press, The Conversation and BBC

This article originally appeared on the South China Morning Post (SCMP).

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