Okay, kiddo, let's imagine a big mountain called Paektu. This mountain is really important to some people who live in a place called North Korea. One day, a long time ago, the mountain started to act a little strange. It was like it was getting sick.
This sickness made the mountain really angry and it decided to throw a big tantrum. The mountain started to shake and make very loud noises. And then, all of a sudden, hot molten rock and ash came spewing out of the top of the mountain.
This is what we call a volcanic eruption. It's like a big burp that a mountain gives when it has too much gas inside. This burp was really violent and it lasted for many days. The hot molten rock and ash covered everything around the mountain and made it really hard for people and animals to live there.
But here's the thing, kiddo. This eruption was so big that it left a mark on the world. It was so powerful that people on the other side of the world saw the sky turn red and the sun disappear. Scientists have studied this eruption and learned a lot about how volcanoes work.
So, even though the eruption of Paektu Mountain was really scary and dangerous, it also helped us learn more about our planet.