If you were to ask an average tourist to rank the threats to their safety while on vacation, volcanic eruption probably wouldn't even be on the list. However, if you travel to locations where active volcanoes exist, there's always the risk of an eruption — and the results can be catastrophic.

This graphic shows the eruption zone of the Bali supervolcano. Source: telegraph.co.uk

This week, the island of Bali was disrupted by clouds of ash and smoke billowing from Mount Agung, and experts have warned that “the potential for a larger eruption is imminent”. As a result, the national alert was raised to its highest level, and all flights at the international airport were grounded. This reportedly left nearly 60,000 tourists stranded on the island, and evacuation orders have been issued for approximately 100,000 people across 22 villages.

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Constant tremors can reportedly be felt on the island, and explosions can be heard echoing miles from the summit. Mount Agung previously erupted in 1963, killing about 1,600 people.

For more updates on the situation in Bali as it unfolds, check out the BBC Asia news feed or monitor #Agung on Twitter. A live interactive diagram of all volcanoes in Indonesia can also be found on the Magma Indonesia web site.

Some might assume the risk of eruption is isolated to tropical islands, but that's not the case. Earlier this year, the Campi Flegrei supervolcano in Italy reached what experts called a “critical state”. An eruption of this volcano would almost certainly affect Naples, Italy, one of the top ten most densely-populated cities in Europe. Here in North America, there is continued concern over the status of the Yellowstone supervolcano.

The infographic below from Kristen Long serves as a primer on the history of major volcanic eruptions, and the relevant elements of a large volcano. Click here to download a full-size version of this graphic.

Written by Patrick McCarthy