When the volcano dome is active and growing, pyroclastic flow activity can be ongoing for many months, but occasionally the whole dome becomes unstable and collapses in a series of pyroclastic explosions. This has happened over several cycles of activity (1997, 2000, 2003, 2006) on Montserrat. Fortunately the volcano crater forms a horseshoe open to the east and the last few major collapses have been channelled towards the uninhabited parts of the island falling straight into the sea.
AVTIS was designed to measure the changing shape of the lava
dome and see which direction the dome is growing in. This
was a brand new use of mm-wave technology and needed three
years of development to prove that the radar would work. If
the dome were to grow so large that it could collapse over
the crater wall to the populated north, then AVTIS could help
show the danger when other observing techniques might fail.
The plan is now to turn AVTIS from a research instrument into
a permanent tool that the Montserrat Volcano Observatory can
use to watch the volcano all year round and help predict where
and when the lava dome might collapse again. The Soufrière
Hills Volcano is the only active volcano in a UK territory,
situated on the southern half of the small Caribbean island
of Montserrat. It is a type of volcano that forms lava domes:
the magma rising from deep inside the earth is particularly
thick and viscous, creating a hot crust of blocky lava at
the surface. During the day the heat cannot be seen because
the surrounding light is too strong, but when night falls
the hot parts glow red showing where the dome is most active.