The searing hot plumes of ash rising above explosive volcanic
blasts often burst with lightning storms, the largest of which
rival the most powerful thunderstorms known on Earth. Now the
most complete and detailed measurements of volcanic lightning
are yielding insights into the roots of these electrical
discharges, and could potentially help avert threats to global
air traffic. Lightning is often seen crackling in the plumes of
explosive volcanic eruptions, such as thatof the Icelandic
volcano Eyjafjallajökull. However, active volcanoes are often
quite remote from civilization and their outbursts are sudden
and unpredictable, which is why scientists have rarely
investigated the origins of this lightning in detail. Even when
scientists can get a close view of eruptions, the intensely
murky nature of volcanic clouds hides most of their lightning
from view. Fortunately, due to seismic activity two months in
advance of the explosive eruption of Alaska's Mount Redoubt in
2009, scientists were able to install four