prize9-4, Exercise 3: Icelandic and subduction-zone volcanoes

Model answer (check the details):

Iceland (divergent, basalt): magma is hot and runny with relatively little trapped gas, so eruptions are often effusive, with lava fountains and flows from fissures. Main hazards: lava flows, gas, and, where eruptions occur under ice, floods and ash. Warning: usually hours to days from swarms of small quakes and ground deformation, with good monitoring.

Subduction zone (for example Japan or the Andes): magma is thicker and rich in dissolved gas and water, so eruptions can be explosive. Main hazards: ash falls, pyroclastic flows, lahars and long-range ash clouds. Warning: signs can build for days to months, but timing and size of a big eruption are hard to predict.

Care: eruptions of both types vary, so say "typically".