Volcanic ash can lead to breathing problems, malfunctions in machinery, and from more severe eruptions, years of global cooling.

The exact cause of the move is still uncertain; however, a severe eruption of Mount Merapi volcano or a power struggle probably caused the move.

Activity thereafter became almost continuous, with relatively severe eruptions occurring in 1660, 1682, 1694, 1698, 1707, 1737, 1760, 1767, 1779, 1794, 1822, 1834, 1839, 1850, 1855, 1861, 1868, 1872, 1906, 1926, 1929, and 1944.

The Hekla 3 eruption (H-3) circa 1000 BC is considered the most severe eruption of Hekla during the Holocene.

The most severe eruption since European times is the Tarawera eruption in 1886.

In a severe Vulcanian eruption of magnitude 3 on the Volcanic Explosivity Index scale, pyroclastic flows rolled over the island.

Bullous pemphigoid causes less severe eruptions that heal faster and are not life-threatening; this condition is seen chiefly in the elderly.

The most severe eruptions on earth in historical time took place in Indonesia.

The island suffered severe volcanic eruptions in 1967, 1969 and 1970.

The drop in temperature was felt all over the world, and was most likely caused by a severe eruption of a volcano in South America.