think about molten rock moving from deep underground to the surface, it often cracks and breaks the rocks that a breach of the crust of the earth. that is one way we look for volcanic levity. we are getting more sophisticated in techniques so we use a lot of satellite observations. it is not as hazardous to get on the ground. we use imaging techniques and this could also be detecting gas from data, it could be looking at changes in the movement by very small amounts and so there is a lot of different ways we can look at how volcanoes are changing their behaviour. monitoring gas on the ground and whether that changes, what is coming out or its temperature. we can lots of ways to try and see any changes in activity. ways to try and see any changes in activity-— in activity. specifically, in the case _ in activity. specifically, in the case in _ in activity. specifically, in the case in the _ in activity. specifically, in the case in the eruption l in activity. specifically, in| the case in the eruption in