Karthala volcano has a permanent lava lake and experienced a sequence of eruptions in April 2005, Nov 2005, May 2006 and Jan 2007. The first 3 took place at the Choungou Chahale crater, which typically contains either a water or lava lake; the last formed a new pit crater to the north (Biggs et al., 2014).
Biggs et al. (2014) present InSAR observations from 2004-2010. The authors find “no significant deformation associated with the first three eruptions, but the January 2007 eruption was associated with ~25 cm of deformation near the volcano’s summit, characteristic of a dyke intrusion aligned with the northern rift zone”.The authors also identify “deformation along the coast which may be attributed to rapid settling of soft sediment or recent volcanic deposits triggered by seismic activity”.
Biggs et al. (2014) propose thatt Karthala volcano, “no deformation is associated with lava lake activity, but when the conduit is blocked, magma intrudes along the rift zone causing deformation”.