describe the internal structure of it?
It is divided into layers by their chemical or physical (rheological) properties. For eg. the outer layer is a chemically distinct silicate solid crust.
Earth
Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties. The outer layer is a chemically distinct silicate solid crust, which is underlain by a highly viscous solid mantle. The crust is separated from the mantle by the Mohorovičić discontinuity. 
what is the diameter of earth in km UNANSWERABLE what is the axial tilt of the planet? Approximately 23.439281°
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Earth [SEP] Internal structure
Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties. The outer layer is a chemically distinct silicate solid crust, which is underlain by a highly viscous solid mantle. The crust is separated from the mantle by the Mohorovičić discontinuity. The thickness of the crust varies from about under the oceans to for the continents. The crust and the cold, rigid, top of the upper mantle are collectively known as the lithosphere, which is the region where tectonic plates are found. Beneath the lithosphere is the asthenosphere, a relatively low-viscosity layer on which the lithosphere rides.