Simplify the following text for a Grade 8 native English-speaking person.
Original: The structure of the Earth , close to the other terrestrial planets , is chemically divided into layers . The Earth has an outer silicate solid crust , a highly viscous mantle , a liquid outer core that is much less viscous than the mantle , and a solid inner core .
Simplified: Chemically , Earth can be divided into the crust , upper mantle , lower mantle , outer core , and inner core .