1. The Earth is divided into (1)crust (2)mantle (3)core. The 3 layers have different thickness and characteristics.

2. Temperature and pressure increases with depth. Therefore, The crust is the coldest. The core is the hottest.

4. Points to be noted : The crust is mainly composed of granite. It forms the distinct landforms and the continents.

5. Points to be noted : The mantle is divided into 2 layers : Upper and Lower mantle. The upper mantle is further divided into 2 layers. The top layer is the lithosphere. The bottom layer is the asthenosphere. The lithosphere consists of hard rocks. The asthenosphere consists of partially melted rock. The crust and the lithosphere overlies this layer and slide on this layer. Very little things is known about the lower mantle.

6. Points to be noted : The core is divided into 2 layers : the Outer and Inner core. The outer core is liquid and is composed of molten metal. The inner core is solid because the pressure is very great. Since the pressure is very great, all the materials inside this layer is highly compressed and this prevents them from melting despite of the high temperature. The inner core is mainly composed of iron and nickel.

7. What is geothermal power ? “Geothermal” is Greek word. geo  earth thermal  heat Geothermal energy is heat from within the earth.

8. Application : Steam and hot water produced inside the earth can be used for 1.heating buildings or 2.generate electricity.

9. Group discussion : How can we make use of geothermal power to generate electricity ?

10. Water pipes can be constructed deep underground. The water is heated up to form steam which moves the turbine. The turbine then drives the generator to produce electricity.

11. Group discussion : Discuss the advantages and disadvantages of using geothermal power.

12. Advantages : Geothermal energy is a renewable energy. (i.e. never exhaused) It causes no pollution. No fuels is required so it is insusceptible to fluctuations in fuel cost.

13. Disadvantages : It needs high technology. (Example : Deep underground water pipes have to be built.) Construction cost is expensive.

14. Hot water from geothermal sources may contain trace amounts of dangerous elements such as mercury, arsenic, and antimony which, if disposed of into rivers, can render their water unsafe to drink.