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The 1983 eruption of Etna began on March 28 after two days of precursory
earthquake activity. A fissure on the south flank of the volcano
produced aa lava that destroyed several restaurants, chalets, and small
buildings. By April 3 the flow was 2 miles (3.5 km) long. By April 23
the flow was 4 miles (6.5 km) long and the threat of inundation to three
towns was high. Photograph of damaged tourist facility by Jack Lockwood,
U.S. Geological Survey, June 5, 1983.
Main vent for the 1983 eruption. The eruption rate was about 10 cubic
meters per second. Photograph by Jack Lockwood, U.S. Geological Survey,
May 27, 1983.
View of 1983 flows from the south-southwest. Photograph by Jack
Lockwood, U.S. Geological Survey, June 1, 1983.
Map based on photograph provided by Jack Lockwood, U.S. Geological Survey.
Less than quarter of a mile (0.5 km) below the vent work began to breach the levee of the lava flow. A diversion channel was excavated and the levee was thinned to only 10 feet (3 m). Placing 900 pounds (400 kg) of dynamite into the hot wall of the levee was a technical challenge. Because of the numerous difficulties and time delays the breach was smaller than originally planned. Only 20% of the flow was diverted out of the main channel. The lava froze in the breach, closing it 2 days later.
Work began in the first week of May on the Monte Vetore barriers. Two
hundred men constructed a rubble barrier about 30 feet high (10 m), 100
feet (30 m) wide. and 1,200 feet (400 m) long. Note approaching aa
flow. Photograph by Jack Lockwood, U.S. Geological Survey, May 28, 1983.
The Monte Vetore barriers are just upslope from the Monte Vetore cone
just to the right of the center of the photo. As lava approached the top
of the barrier more rubble was added to increase the height of the
barrier. The lava overtopped the first barrier, even though additions
had doubled it in size. A second barrier was constructed about 300 feet
(100 m) to the west. The two barriers contained the west margin of the
flow field. Photograph by Jack Lockwood, U.S. Geological Survey.
More barrier were constructed to protect the main tourist complex on
Etna. The Sapienza barrier is named for the main building in the
complex. Photograph by Jack Lockwood, U.S. Geological Survey.
Thirty feet (10 m) thick aa flow approaching the Sapienza barrier. The
flow add a layer about 6 feet (2 m) thick to the top of the barrier but
did not go beyond. Photograph by Jack Lockwood, U.S. Geological Survey,
May 28, 1983.
The Sapienza barrier on May 31. The barrier remained intact until the
eruption ended on August 6. Photograph by Jack Lockwood, U.S. Geological
Survey.
Aerial view of aa flow against the Sapienza barrier. Photograph by Jack
Lockwood, U.S. Geological Survey, June 1, 1983.
The barriers prevented lateral spreading of the flow field into developed areas. It has been estimated that damage caused by the flows if the barriers had not been built would be $5-25 million. Total cost of the diversion was $3 million. It was the first time that earthen barriers successfully diverted lava. It also demonstrated that volcanologists could actively direct intervention in Volcanic processes.