I have to deliver a 30-40 minute earth science lesson to above average high school students for an interview.?

I am looking for some suggestions. Timing must be no less than 30 minutes, no more than 40 minutes. I was told not to simply lecture the whole time (wasn't planning to). They are looking more at how I engage students, and my organization/ clarity. I'm not asking for help on the mechanics, but some general activities/lab to do. I am assuming I have no materials to work with other than a black board, and very little prep time before the lesson begins. It will be the first time I see the students, so I will not have any rapport with them... Thank you for your help!