When does a volcano explode? And when does it erupt more gently, without an explosion? It's a question volcanologists are seeking to answer. No one can look inside a volcanic vent. But laboratory experiments can show how magma erupts and explodes.
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00:00 No two volcanoes are alike. Some erupt by spewing lava, gas and rocks into the air.
00:07 Others are relatively gentle. We can't look inside a volcano, of course,
00:12 but in the lab we can show how magma explodes.
00:16 Magma has very different properties. It can be more like a tar you make the street with.
00:24 So if you very slowly deform it, it can flow, but if you fastly deform it, it accumulates stress and it breaks.
00:32 That's exactly what happens in explosive volcanisms.
00:35 This cylinder was carved out of a large chunk of volcanic rock.
00:40 To simulate a volcanic explosion, Bettina Scheu places a cylinder inside a model volcanic vent.
00:47 Gas is then fed into it, raising the pressure inside.
00:51 Until it splits into fragments of volcanic material like cinder, ash and broken rock called pyroclasts and explodes.
01:01 The experiment shows what happens in the conduit when the volcanic matter is ejected upward at an ever-increasing velocity.
01:08 And how a cloud forms above a volcano.
01:20 This gives us the possibility to observe it with a high-speed camera and really see where it fractures, why it fractures.
01:28 How coarse are the grains, how large are they, how are they evolving and how is the ejection of that
01:35 then creating the plume and creating the ballistics being ejected from the volcano which pose the hazards.
01:42 The research team could even observe lightning forming in the cloud when particles of volcanic ash fragment and collide.
01:49 They found that the smaller the particles, the more lightning there is in the plume.
01:54 In 2022, the volcanic eruption in the South Pacific country of Tonga sparked the most intense lightning storm ever observed.
02:01 Each volcano is just like personalities, they have different personalities.
02:05 So you have to study for each volcano how they behave and with this we can improve the forecast.
02:11 But we can't do a forecast on that.
02:14 The volcanic rock here in the Munich Laboratory comes from around the world.
02:19 Because every volcano is different in their shape, vents, porosity, magma composition and more.
02:26 Every volcano has its own personality and every eruption does too.
02:33 (engine revving)