Mont Pelée Eruption and Dust Falls

FALLS of dust are caused in two ways; either the dust, as for instance Sahara sand, is transported by means of the lower air-currents over wide areas, or matter is ejected from volcanoes, thrown high up into the air and carried by the upper currents, falling eventually in places at great distances from the seat of disturbance. The eruption of Krakatão is a good example of the latter case, while the dust fall that occurred last year in March and was recorded in northern Africa, southern and northern Europe is a good representation of the former kind of dust fall.