The skin of the apple will represent the crust of the Earth. The teacher will point out how thin the skin is in comparison to the "meat" and the core. Explain to the students that the crust compared to the rest of the Earth is much thinner than the skin is to the rest of the apple.

The "meat" of the apple will represent the mantle of the Earth. Explain to the students that the mantle is the largest layer of the Earth. The mantle is composed of molten rock that is in a semi-plastic state. The mantle's composition is similar to very hot asphalt.

The core of the apple will represent the outer and inner cores of the Earth. Make sure that the students understand the Earth's core is composed of two layers. Point out that the core is like a little round ball in the middle of the Earth. The outer core is actually composed of very hot liquid metals, nickel and iron. The inner core is composed of the same nickel and iron but in a solid state because of intense pressure.

The fourth layer, the Inner Core, is composed of very, very hot metals (iron and nickel) with pressures so great that the metals do not flow as a liquid, but are forced to vibrate in place like a solid. Earthquake waves that reach this layer move at the greatest speeds because waves move through solids faster than through gases and liquids.

Today scientists believe that the crust and the rigid, outer zone of the mantle makes up a layer that is called the Lithosphere . The lithosphere is broken into 12 large pieces that are called plates. The zone directly under the lithosphere is made of a flowing, denser layer called the Asthenosphere.

Watch the videos and pay particular attention to:

1. various states of lava.
2. the link between earthquakes and vlcanoes.
3. the behaviour of undersea volcanoes.