Pompeii was two natural disasters. 17 years (which may seem along time but isn't really) before the eruption there was an earthquake measuring around 5-6 on the richtor scale. Pompeii was used to having small tremors but it was quite rare to have one that big. After the earthquake many people didn't rebuild and moved to nearby cities. If that earth quake hadn't of happened quite a few more people would of lost their lives. 17 years later Mt Vesuvius erupted. to start with it looked just like a big black cloud of smoke. Then after that it looked like a huge fire burning up the top of Mt Vesuvius. A volcano hadn't happened in the roman empires time so no-one knew exactly what it was.When the actual eruption happened mud, ash and rock flowed down the volcano and through the city, Killing lots of the residents and preserving everything in a very thick layer of debris, ash and pumice. Archeologists think from the bodies they found that the deaths happened very fast, in around a second. This is because the bodies show no sign of reaction to the boiling hot tempretures of the mud. Quite a few cities around Mt Vesuvius had the same problems as Pompeii but Pompeii was the most famous. This natural disaster caught people of gaurd and was very unexpected like the Christchuch earthquake.