It was a normal summer day in ancient Rome. People were shopping, cooking, chatting—just going about life like usual. But in the shadow of a nearby mountain, something terrifying was building up.

That mountain was Mount Vesuvius. And on one terrible day in 79 CE, it erupted with such power that it completely buried the Roman city of Pompeii. Thousands of people were caught in the ash and smoke. Buildings vanished under hot volcanic rock. Today, we remember the Pompeii eruption as one of the most famous volcanic disasters in history. But how did it all happen—and what did we learn from it?