Harmonic tremor

Harmonic tremor is when the Earth shakes in a special way that sounds like a low hum. This can happen when a big volcano is getting ready to erupt.

When a volcano is about to erupt, it can make lots of different sounds as things move around inside it. One of these sounds is harmonic tremor. It happens because hot rocks and gas are moving around inside the volcano, which makes the Earth shake.

The shaking happens in a special way that scientists can measure with special machines called seismometers. They look kind of like robots with arms and they can tell us how much the Earth is shaking and in what way. Scientists use this information to figure out how big the earthquake is and how far away it is from us.

This is important because if a big volcanic eruption is about to happen, we want to know about it as soon as possible. So when we hear the low hum of harmonic tremor, it helps us prepare for the volcano to erupt and keep people safe.