Carefully poke a hole in the center of one large marshmallow. Next, wedge a single spice drop into the center of the marshmallow.
Put one tablespoon of butter and 12 marshmallows into the microwaveable bowl and then microwave on high for one minute. Remove the bowl from the microwave and stir with the wooden spoon and then place in the microwave for another minute.
Put two cups of crispy rice cereal into the bowl of marshmallows. Stir the mixture while it is warm, coating the cereal with the marshmallow mixture. Allow to cool for one minute.
Flatten the mixture of cereal with a spoon and then place the marshmallow covered spice drop in the center. Wet your hands with water and then fold the cereal mixture around the spice drop. Roll it in the bowl or on a paper plate with the palm of your hand until it is a densely packed ball.
Cool the rice cereal ball in a freezer for 15 minutes. Next, place the ball on a paper plate and cover with the candy sauce, just enough to cover the entire cereal ball. Let the candy harden on the ball.
Hold the ball steady and cut it directly down the center, creating two equal halves. The model of the Earth's layers are now distinctly visible: The candy sauce is the Earth's crust, the cereal is the mantle, the center marshmallow and the spice drop are the outer and inner core. Allow kids to devour the Earth.