Use a sharp knife to cut a straight line cleanly through the center of the foam ball. Cut so both halves are equal when taken apart.
Remove the top of the foam ball and place both pieces of the ball on the rounded side so the inside of the ball faces upward.
Measure the width of the inside of the foam ball so you can accurately measure the size of each portion of the interior of the Earth before you begin creating the layers. The inner core, outer core, mantle and crust are the four portions of the Earth you need to create. Divide the width of the foam ball into four sections sized as follows:
Inner Core-- .7 percent of the total width of the foam ball; located at the center
Outer Core--15.7 percent of total width; surrounding inner core
Mantle– 82 percent of total width; surrounding outer core
Crust– 1.6 percent of total width; surrounding mantle
Color the inner core of the Earth red to represent the solid iron that makes up the inner core. Color the outer core yellow to represent the liquid iron that makes up the layer. Color the mantle gray or orange to represent iron and magnesium and the crust gray or white to represent rocks rich with silica. Use markers for the best result.
Put the foam ball back together and create the outside of the Earth by coloring it to look like the Earth does from space. Use a globe or a photo of the Earth to color shapes in green that resemble the continents Earth is made up of and blue to color in the Earth’s water supply.