This is what a volcano eruption looks like. Note the red lines. That's where the poor little seismometer thingy loses its lunch. Poor thing. They lost a couple of these gadgets, I read. Probably a million each. Money well spent, actually. As a neighbor of volcanoes, I like to know when they are having a party.
The course might be surprising, may not even go in one direction, and we hope to get lost, though we do hope to know where we are at all times. That little characteristic often is the difference between a good voyage and a disaster.