The eruption sequence that began in 1989 culminated in 1991-93
with the greatest lava outpourings this century from this
consistently active shield volcano. Settlements downslope that
were threatened by the lavas were perhaps spared by the lava
barriers built in 1991 and 1992 ( Barberi et al., 1993).
Microgravity and other monitoring methods have provided a detailed
picture of magma movement, and of controls thereon, before and
during the eruption ( Rymer et al., 1993). Etna is one of a
few volcanoes so far recognized in which the gravitational
spreading of the edifice may play a major part in controlling
tectonic and volcanic history ( Borgia et al., 1992), with
obvious ramifications for future hazard monitoring. The SO
flux from Etna, one of the highest in the world at over 6000 tons
per day, was recently measured remotely from an aircraft using
thermal infrared (8-12 micron) techniques ( Realmuto et al.,
1994), thus pointing the way toward providing an independent
measurement of sulfur gas emissions determined with the much
coarser-resolution, satellite-borne TOMS instrument
( Bluth et al., 1993).