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Rocks and Minerals
Lesson 10 Rocks
1. The age of the Earth-
The Earth is about 4.6 billion years old.
2. How the layers cooled-
As the Earth cooled the heaviest and densest materials sank to the center, and the lightest materials rose to the top. The heaviest materials are the metals iron and nickel, which makes up the inner and outer cores. The lightest materials are rock and make up the crust and upper most region of the mantle.
Rocks are composed of two or more minerals. These minerals have been 1) cemented together 2) squeezed and heated together, or 3) melted and cooled together Rocks make up the vast majority of the Earth's crust. The two most common rocks on the crust are granite and basalts.
A mineral is a solid that is composed of one substance that occurs naturally on Earth.
Soil is composed of very small, weathered fragments of rock along with organic (decomposed or decomposing plant and animal material) material.
6. Rock Cycle-
The rock cycle is the process in which igneous, sedimentary, and metamorphic rocks are changed over time. Igneous rocks are formed by volcanic activity. Metamorphic rocks are igneous, sedimentary, or other metamorphic rocks that have been changed by heat, pressure, chemical means, or a combination of all or some of the above. Sedimentary rocks are formed from the weathering of all of the rock types and the cementing, compressing, or recrystallization of the sediments.