Can humans stop or prevent lava flows?  Occasionally lava flows threaten human settlements and infrastructure.  In 1973, lava flows from Eldfell volcano, Heimeay,  moved into the town and threatened the port of Vestmannaeyjar, Iceland.  In 1984 the city of Hilo, Hawaii was faced with an approaching lava flow.  Lava flows from Etna have destroyed or threatened towns and structures on numerous occasions: 1928—Mascali; 1971—Etna Observatory; 1981—Randazzo; 1992—Zafferana.  Being slow  moving and low energy, there have been successes and failures in multiple attempts to slow or divert the flow of lava. 

12.2.1  Diversion techniques  Bombing lava flows has been a discussion topic for many years and has been attempted during eruptions at both Mauna Loa and Etna.  The idea is to breach and block a lava tube or alter the spatter-cone allowing the lava to flow in an alternate direction.  This was first attempted at Mauna Loa in 1935 and again in 1945 both times without significant success (Lockwood & Torgerson, 1980).  More attempts were made in 1975 and 1976.  During these attempts on four different occasions, 36 bombs were dropped on and an erupting spatter cone and tube-fed pahoehoe flows (Lockwood & Torgerson, 1980). 

Barriers and levees have also been used to divert lava flows and can be successful in low volume effusive eruptions as seen at Etna in 1992 and at Heimaey in 1973 (photos below).

12.3.3 Slowing the lava flow by cooling it has been proposed attempted as another method for controlling lava.   that strong endothermic dissociation reactions of carbonate rocks (such as dolomite or limestone) will rapidly cool lava flows, making them more viscous and able to solidify more rapidly (Schuiling, R.D. 2008).

Lava cooling was successful during the 1973 eruption at Heimaey when used in conjunction with diversion barriers.  Sea water was pumped and spread on an advancing lava flow.  The water cooled and increased the viscosity of the lava.

Photo by Jack Lockwood, U.S. Geological Survey May 28, 1983

Successful Lava Diversion, Etna, 1983.  From Oregon State University

 

Concrete blocks dropped near and through a skylight.  Etna, 1992

Image courtesy of Claude Grandpey.  Obtained from Big Think

GE5185 Volcanology - Fall 2011

Big Ideas in Volcanology

12.2 Controlling Lava Flows