Mechanism of energy transfer in the lava lake of Niragongo (Zaire), 1959–1977

Heat and mass transfer rates were studied at the Niragongo lava lake during two expeditions directed by H. Tazieff in 1959 and 1972. The results of this study are as follows:Heat is transferred to the surface of the lake by the movement of lava; gas discharge is a result and not the cause of convection. The chemical composition of the gases and magma has changed very little between 1959 and 1972, whereas the mass and energy outputs differ by an order of magnitude. In 1977 a catastrophic explosion seems to have been caused by tectonic factors, stopping the slow convection of magma under the volcano and hence reducing surface manifestations in the form of the lava lake and escaping fumarolic and magmatic gases. The gas discharge was, in tons day⁻¹, 5000 for H₂O, 11,000 for CO₂, 1000 for SO₂ in 1959, and in 1972 7700 for H₂O, 180,000 for CO₂ and 23,000 for SO₂. These values correspond to an energy transfer of 0.9 × 10⁹ W in 1959 and 16 × 10⁹ W in 1972.