You can do the introduction in one of two ways:
1. Read this article with your students - "City Under Ash" which talks about Pompeii and how it was discovered and preserved. There is a question sheet and a powerpoint to go over afterwards.
2. Watching the video below from Nova - you'll need to make up your own question sheet, I've provided a question sheet from a National Geographic Video called "The Fire Within" if you're able to find it - it's a great video resource
2.Natl Geo The Fire Within.doc - This question sheet DOES NOT match the video below - you'll need to make your own