How volcanoes work, explained by a volcanologist

How volcanoes work, explained by a volcanologist
How volcanoes work, explained by a volcanologist
Volcanologist Janine Krippner dives into the details of how volcanoes work and the different types of lava flows.
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SPEAKER: Lava flows erupted in fiery fountains. Materials thrown up from the earth's interior have transformed this land.

JANINE KRIPPNER: What a volcano is is any point on the earth where magmatic products are coming out at the surface. What I mean by magmatic products is below the surface, magma is molten rock, very, very hot. It comes from hundreds of kilometers below the surface and then makes its way up depending on what areas of the earth we're looking at.

So lava is once we have it at the surface. Below that, we call that magma. There's a lot of gas in magma. Some of that is coming out as it's moving. Some of it is trapped within it. So that'll dictate what kind of eruption you have. So you might have it exploding. Like if you shake up a bottle of Coke and open the cap off, the gases are coming out really, really quickly, blowing the liquid apart.

We have ash going up into the air. Ash is the tiny particles of rocks that are produced when that happens, or is it more like a runny lava flow or a thick viscous or sticky lava flow? So any of those processes happening at the surface is what we call a volcano. And normally, all of these products, which are variations of rock built up around the vent, and that's when we get sometimes really big mountains or much smaller hills.

And sometimes, if you have a really, really big eruption, it can actually produce a collapse. So the ground collapses inwards afterwards, and then you just have a big hole. So there's a big variation in different volcano types and what they look like there as well. You might have seen videos of lava flows.


So a lot of amazing footage of this really bright orange or red stuff moving along the surface after it comes out at a volcano, and what that is is it's actually melted rock. So if you think of any rock around you, think of how hot it would have to get to actually melt that rock. This isn't something you can just chuck in the oven and melt.

Lava tends to be around 800 degrees Celsius all the way up to around 1,200 degrees Celsius. So this is really, really hot. You could be meters, meters, meters away from this lava flow and still feel the heat intensely on your skin. It's that hot. So the range of that is partly depending on what type of magma or lava you have, and that's depending on the chemistry.

A large part of it is silica. The silica content. So the higher the silica content, the stickier or more viscous the lava is or the magma. And so you can have the low viscosity, very high temperature lavas which flow quite fast. You might see a lot of videos like that coming out of Kilauea in Hawaii, or some of them are much, much cooler or still hot for us at around 800 degrees Celsius, and those move much slower.

They can be much, much thicker, and in fact, they can be meters to tens of meters thick. So the velocity or the speed of those will drastically depend on the temperature, how fast that's coming out of the vent, and of course, that tells us what the impacts might be to the surrounding landscape as well.

VINCE (OVER RADIO): This is Vince calling observatory. It looks like a new episode is starting. We've got a good-sized fountain and a strong lava flow.

JANINE KRIPPNER: A pyroclastic flow is a really dangerous, really chaotic mix of hot volcanic gases and hot volcanic rock. So the volcanic rock can be really tiny so less than two millimeters in size. That's what we call volcanic ash, or it can be the size of a large car or even bigger. So this huge jumble of hot rock-- the hot rock I'm talking about is usually hundreds of degrees hot.

So they can get up to around 800 or 900 degrees Celsius so extremely hot and extremely dangerous. They can also move very, very, very quickly so you cannot outrun these. Usually, we're talking about tens of meters per second or even a couple of hundreds of meters per second. So if you think of how far 100 meters is, and if you can try to imagine racing that in a second, like that's just so fast it's even hard to comprehend.

When looking at how many active volcanoes there are around the world, for a volcano, we call it young if it's erupted within the last 10,000 years. So if it's reproduced any kind of eruption in the last 10,000 years, we'd call that potentially active or dormant. We have around 1,300 of those in many, many different countries.

On any given day, there's usually between 40 or 50 ongoing eruptions around the world, and most of these we never hear of because they're quite small. They might just be producing some little ash plumes into the atmosphere every now and again. A dormant volcano is one that might not have erupted in a long time.

So for us, 10,000 years seems like a long time, but in the lifetime of a volcano, that's actually not that long considering some volcanoes might be over a million years old. So extinct is where we think of volcano is probably never going to erupt again. A lot of people live near active or dormant volcanoes.

We're talking about well over 100 million people living within very short distance of potentially active or even erupting volcanoes, which is why it's so important to understand what volcanoes do and how we can help prepare communities to be safe.