Published on August 7, 2014
silicon calcium, sodium potassium, iron. There are 8 elements that make up 99% of the Earth’s crust. The continents are about 35 km thick and the ocean floors are about 7 lm thick. The Mantle is the solid casing of the Earth and is about 2900 km thick. It makes up about 70% of the Earth’s mass (68.1%). It is made up of silicon, oxygen, aluminum and iron. The Core is mainly made of iron and nickel and makes up about 30% of the Earth’s mass (31.5%). The Outer Core is 2200 km thick and is liquid and the Inner core is 1270 km thick and is solid. ROCKS The rocks you see around you - the mountains, canyons & riverbeds, are all made of minerals. A rock is made up of 2 or more minerals. Think of a chocolate chip cookie as a rock. The cookie is made of flour, butter, sugar & chocolate. The cookie is like a rock and the flour, butter, sugar & chocolate are like minerals. You need minerals to make rocks, but you don't need rocks to make minerals. All rocks are made of minerals. For a LIST of ROCKS , check out Wikipedia's List of Rocks http://en.wikipedia.org/wiki/List_of_rocks For some PHOTOGRAPHS of ROCKS , look here . MINERALS A mineral is composed of the same substance throughout. If you were to cut a mineral sample, it would look the same throughout. There are about 3000 different minerals in the world. Minerals are made of chemicals - either a single chemical or a combination of chemicals.