Big eruptions and their consequences

In 1991, Mount Pinatubo on the island of Luzon, in the Philippines, erupted just 90km (55 miles) north-west of the capital, Manila.

Over the course of several eruptions, the volcano ejected a massive 10 cubic km of material, making it the second biggest eruption of the 20th Century.

While volcanic dust is in the upper atmosphere, it can have a profound short-term effect on the global climate, because it blocks out a portion of the sunlight able to reach the ground.

The Mount Pinatubo eruption caused the average global temperature to drop by 0.4-0.5C.

Previous eruptions have been much more deadly. The eruption of the volcano on Krakatoa in Indonesia in 1883 is one of the best known eruptions in relatively recent times, because it occurred after the invention of the telegraph.

It killed thousands, pulverised two-thirds of the island and drastically altered the ocean floor. But Krakatoa was a mere baby compared with the eruption of Tambora, also in Indonesia, some 68 years earlier.

This was the most powerful eruption in recorded history. Rivers of hot ash rolled down the 4,000m (13,000ft) -high volcano, killing around 10,000 people on the island.

It is thought to have ejected 50 cubic km or more of material and pumped vast amounts of sulphur dioxide into the atmosphere.

The cloud from Tambora caused an unusual chill, lowering global temperatures by an estimated 0.4-0.7C.

In parts of Europe and in North America, 1816 became known as "the year without a summer". Frosts killed off crops in New England and Canada; Europe was also hit badly.