Name: 火山音乐如何帮助我们预测它们（How Volcanoes’ Music Could Help Us Predict Them）
Uploaded: 2021-05-19T08:52:14.000Z
Duration: 4 min 24 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

From ancient times to today, volcanoes have destroyed and threatened

And even though we have some ways of monitoring and predicting

their activity, we still don't have a surefire way to tell

And yet, nearly one in ten people lives within 100 kilometers

So, in search of more reliable ways to monitor volcanic activity,

some scientists have started looking at volcanoes' music.

You might not think of volcanoes as especially musical,

It's just infrasound, whose frequency is below the threshold of human hearing.

These sound waves can come from different phenomena, like gas

getting pushed out of vents or out through the surface of a lava lake.

And that moving air acts kind of like air moving through

a wind instrument: It makes different sounds based on

Just like a horn's sound changes based on the shape and flare

of the bell, a volcano's sound can change depending on the shape

For instance, a volcano with a deep crater might produce a deep sound,

while a volcano with a shallow crater would produce a higher-pitched sound.

Meanwhile, narrow craters also resonate for longer periods of time,

while wide, dish-like craters might not even resonate at all.

And finally, the flare of the crater's rim changes the sound's timbre,

which you can think of as the color of the sound.

It's like how a flute and oboe sound different even when they're

Since these sounds are so tied to the volcano's shape,

they can change anytime the volcano changes shape.

Which is not uncommon—especially when a volcano is getting ready to erupt.

It all begins when the pressure of magma starts mounting beneath the surface.

This causes lots of little earthquakes around the volcano

that can shift around rocks and other geological features.

The pressure can also make crater walls change their shape,

kind of like how a balloon's shape changes as it inflates.

Eventually, those crater walls can even fracture.

On top of that, if there's a lava lake within the crater,

the mounting pressure can cause it to rise.

So, before a volcano erupts, the entire internal structure

And all of this changes the volcano's sound.

One recent example of this happened in Chile in 2015.

On March 3 of that year, Chile's Villarrica volcano erupted.

It spewed lava and ash up to a kilometer up in the air for

about 20 minutes—and then it all went quiet.

As far as eruptions go, it wasn't so remarkable.

Some property was damaged, but no one died, and the volcano

But the Villarrica eruption is important because it's one of

the few cases where a volcano's sound was being monitored

And scientists actually observed a shift in Villarrica's sound

on March 1, 2015, two days before the eruption.

For one, the frequency of the sounds increased,

The sound waves also got broader, marking a change

And finally, the volcano lost its resonance.

Before March 1, Villarrica's sound was reverberating in the crater,

which is shaped like an upside-down funnel.

But after March 1, those reverberations stopped.

That told researchers that something had changed—something inside

And by the next day, new infrasound readings suggested that

the lava lake, which was normally deep inside the funnel,

had actually risen to nearly the rim of the crater.

At the time, scientists didn't realize that they had been listening

to evidence of an eruption about to happen.

They only put all the pieces together after the fact.

But now, scientists are looking at how they might be able to use

data like this to predict eruptions in other,

It's tricky because there's no “normal” volcano sound.

Every volcano has its own sound, so the only way to tell

if something is off is to detect a change.

And even the type of change is different from one volcano to the next.

But by researching volcanoes for a long time, scientists

can learn what different volcanoes sound like so they know

No matter what, it's unlikely that this technique will

completely replace traditional methods of monitoring volcanoes,

This is one more tool that we can use to protect ourselves

And there's something kind of beautiful about the fact that

Thanks for watching this episode of SciShow!

And if you want to learn more about volcanoes,

you might enjoy our episode about the biggest eruptions