This is a project I usually give as extra-credit, but depeding on the socio-economic status of your stuents, you could very well require everyone to create a model showing the major features of the ocean floor. The students really love doing projects like this. So, I always like to have something extra credit or hands-on for the higher order thinking students. I just know that times are tough for a lot of people and don't feel comfortable requiring them to go out and by all of these materials, b/c no matter how many times you say it can be shoe- box, you are probably not going to get one. It is a wonderful project idea, and the students realy get into it!