As can be seen in the above video, the collapse first brought a cloud of dust and then caused a large ejection of molten lava high into the air, which was thrown in the direction of the new earth banks that have been erected to try and stop lava flowing in the direction of the Suðurstrandarvegur road.
Work continues on the earthworks designed to divert lava away from Nátthagi, from where it could flow towards the coast road, and instead keep in in the natural basin of Meradalir. The earthworks are likely to be eight metres tall in the end, rather than the originally-planned four metres.
It is not yet clear how effective the human efforts will be against the forces of nature, but the engineer in charge believes trying is worth the effort and the fairly modest cost.
Alternative routes are available in the event that part of the road does eventually succumb to lava. No communities would be cut off and access for volcano visitors would also continue.