The document discusses the structure of the Earth by comparing it to an apple. It explains that both have a thin outer crust/skin, a thick inner core, and layers in between. The Earth has an inner solid core and outer liquid core of iron and nickel. Between the core and crust is the mantle, made of solid but hot rock. The crust floats on the mantle and is divided into thinner oceanic crust and thicker continental crust made of different materials.

1. The Earth’s Structure

3. The Earth’s Interior Ever wondered what our earth is made of? Think of it as an apple. An apple constitutes the skin, the pulp and the core in the middle. Similarly, the earth is made up of the thin outermost layer called the crust, the innermost part called the core, and the part in between them called the mantle. (Fig 1.1) The apple and the structure of the Earth

4. At the beginning, the early earth seemed to have heated up, the centre became molten, and convection currents developed as the lighter compounds tended to rise towards the surface forming the brittle crust. Together with the top part of the mantle, it formed the hard slabs known as lithosphere. The continents are embedded in these slabs. The lithosphere is divided into oceanic and continental crusts. Oceanic crust (sima), the floor of the deep oceans, is thin, about 7km thick, and made of relatively dense rocks like basalt. Continental crust (sial) is much thicker, averaging 33km, and is composed of relatively light material such as granite. (Fig 1.2) The Crust (Oceanic and Continental).

5. The denser materials such as iron sank to form the core. It is partly solid. Temperatures are extremely high, at about 3000oC. (Fig 1.3) The Core. Between the core and the crust, the intermediate zones form the mantle, which is mainly solid rocks but there is also a layer of molten rock called magma nearer the core. Temperatures are high, at about 2000oC. Fig 1.4) The Mantle.

6. The Earth’s Structure THE CORE The inner part of the earth is the core. This part of the earth is about 2,900 km below the earth's surface. The core is a dense ball of the elements iron and nickel. It is divided into two layers, the inner core and the outer core. The inner core - the centre of earth - is solid and about 1,250 km thick. The outer core is so hot that the metal is always molten, but the inner core pressures are so great that it cannot melt, even though temperatures there reach 3700ºC. The outer core is about 2,200 km thick.

7. The Earth’s Structure THE MANTLE The layer above the core is the mantle. It begins about 10 km below the oceanic crust and about 30 km below the continental crust (see The Crust). The mantle is to divide into the inner mantle and the outer mantle. It is about 2,900 km thick and makes up nearly 80 percent of the Earth's total volume.

8. The Earth’s Structure THE CRUST The crust covers the mantle and is the earth's hard outer shell, the surface on which we are living. Compared to the other layers the crust is much thinner. It floats upon the softer, denser mantle. The crust is made up of solid material but this material is not the same everywhere. There is an Oceanic crust and a Continental crust. The first one is about 6-11 km thick and mainly consists of heavy rocks, like basalt. The Continental crust is thicker than the Oceanic crust, about 30 km thick. It is mainly made up of light material like granite.

9. Earth’s Structure Notes Liquid solid About 2300km About 1200km Outer Core Inner Core Rigid Plastic – will flow very slowly Upper 100km Total about 3000km Mantle Solid, rigid 6km under the oceans; Average 30-40km; Up to 70km under continents Crust State Thickness Part of the Earth

13. Complete the table below to record some of the characteristics of the layers of the earth