ocr: Earth For about 500 million years after its initial formation, the planet remained at a rather stable 2000 degrees Fahrenheit (874.68 degrees Celsius). Comprised predominantly of iron and silicates, the planet also contained small amounts of radioactive elements, mostly uranium, thorium, and potassium. Geology Between the ironcore and the solidrock crust lies a mantle ofheavy silicate rock that is 1800 miles thick (2880 kilometers). The mantle 1S neither solid nor liquid, but has a viscous, yielding consistency upon which the crust actually floats. The crust 1S not a single, solid mass, but ra ...
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