A model of the Earth's layers can double as a tasty snack when you use food to make each layer. This project can take the form of a ball, or you can place the layers one on top of the other in a clear plastic cup to be viewed as a cross-section of the Earth's layers. You model should include the inner core, outer core, mantle and crust.
The planet's inner core is a solid ball composed mainly of iron and nickel. A number of small edible items will work for an inner core: chocolate chips, a gumdrop or hard candy like a cinnamon drop or peppermint. The inner core will either be the center of your ball-shaped Earth layers model, or will sit at the bottom of a clear plastic cup containing the layers.
The outer core is an extremely hot molten layer, also composed mostly of iron and nickel. Something a bit softer, like jelly or a marshmallow, can stand in for this layer. To use jelly, form your mantle food into a ball, cut it in half, scoop out a small pocket in the center of each side, spoon in the jelly and embed the solid inner core inside the jelly. Then press the two halves of the mantle back together. Of course, this only works when your mantle food is solid enough to allow it. Otherwise, squish a marshmallow around your inner core. Another option is to simply use one piece of candy to represent both the inner and outer core, but this is a less accurate solution.
The Earth's mantle is a hard layer that moves very slowly around the outer core. It is the thickest layer. Ice cream, peanut butter or melted marshmallows with puffed-rice cereal can all work for the mantle layer of your project. Push a hard candy representing both the inner core and outer core into a ball of ice cream, or spoon a layer of ice cream into a clear plastic cup over the top of the inner and outer core. Chocolate pudding is also a tasty mantle if you are putting your layers in a cup, but remember that the mantle is solid, not molten. Another idea for the mantle is to mix peanut butter with powdered sugar to form a firm dough and roll it into a ball around the core. If peanut allergies are a problem, opt for puffed-rice cereal stirred into melted marshmallows and formed into a ball.
The Earth's crust is the rocky surface layer of the planet. It ranges from about 3 to 50 miles thick in places. To make an edible crust, crush graham crackers or dry chocolate cookies and roll your model's sticky mantle in it to form a crust, or pour a thin layer of the crumbs over the top of your plastic cup model. Another tasty option is to use chocolate shell sauce, which hardens when poured over frozen ice cream (or your Earth model's mantle). Put your Earth in the freezer for 15 minutes, then take it out and pour chocolate shell sauce over it and let it harden.