The activity at Hengil is man made, they pump water down geothermal bore holes to generate steam to drive turbines, and other uses. The activity at Katla is ongoing and is a case of watch this space. The North American and Eurasian tectonic plates have been unusually active at Reykjanes ridege and Tjornes fracture zone - that is both to the North and South of Iceland - putting immense stresses on the land mass, plus the magma plume that lies below Iceland. It could go anywhere on the fault at any time - my attention is firmly on katla, however I am particularly worried that we may see multiple fracture zones open up at the same time due to the unusually high stresses cause by eruptions being 'overdue'.