The earth is made up of three layers, the crust, the mantle and the core. The top most layer is the crust. It is made of solid rock, and under the continents it is about 30 to 50 kilometres thick.
Next layer, the mantle, goes down to a depth of 2900 kilometres. It is also made of solid rock. The inner most part of the earth is the core, which is about 33800 kilometres in radius. Because of the great heat the material of the core is liquid. So scientists have suggested that there is an inner core of solid metal about 2575 kilometres in diameter.
One theory about the origin of the earth is that it was originally swirling eddy of gas and dust. Some of the gas flowed away into space. The dust collected together because of gravity and became the solid earth. Trapped in the solid earth there were radioactive elements. Radioactive elements continuously break down, producing heat. The radio active heat gradually raised the temperature of the earth. Eventually the dust inside the earth began to melt.
Next layer, the mantle, goes down to a depth of 2900 kilometres. It is also made of solid rock. The inner most part of the earth is the core, which is about 33800 kilometres in radius. Because of the great heat the material of the core is liquid. So scientists have suggested that there is an inner core of solid metal about 2575 kilometres in diameter.
One theory about the origin of the earth is that it was originally swirling eddy of gas and dust. Some of the gas flowed away into space. The dust collected together because of gravity and became the solid earth. Trapped in the solid earth there were radioactive elements. Radioactive elements continuously break down, producing heat. The radio active heat gradually raised the temperature of the earth. Eventually the dust inside the earth began to melt.
