Magma build-up may put Salvadoran capital at risk

The build-up of magma six kilometres below El Salvador's Ilopango caldera means the capital city of San Salvador may be at risk from future eruptions, University of Bristol researchers have found. A caldera is a large cauldron-like volcanic depression or crater, formed by the collapse of an emptied magma chamber. The depression often originates from very big explosive eruptions. In Guatemala and El Salvador, caldera volcanoes straddle tectonic fault zones along the Central American Volcanic Arc (CAVA). The CAVA is 1,500 kilometres long, stretching from Guatemala to Panama. The team, from the Volcanology research group at Bristol's School of Earth Sciences and the Ministry of the Environment and Natural Resources in El Salvador, studied the density distribution beneath the Ilopango caldera and the role tectonic stresses - caused by the movement of tectonic plates along fault lines - have on the build-up of magma at depth. The Ilopango caldera is an eight km by 11 kilometre volcanic collapse structure of the El Salvador Fault Zone.