The inner core has not always existed, but formed over time. ...

[sdfghj]

The inner core has not always existed, but formed over time. Explain how conditions in the Earth changed over time to create an inner core.
 
  What will be an ideal response?

Question 2

Scientists have subdivided the upper mantle into three sections based on environmental and compositional differences. What are these three subdivisions and how do they compare to each other?
 
  What will be an ideal response?

[LP]

Answer to Question 1

Props to you, cheers.

Answer to Question 2

Answer: The uppermost mantle is the lithospheric mantle, which is slightly lower in density and solid. Next down is the asthenosphere, which is similar in peridotite composition to the lithospheric mantle, but is hotter and less rigid, thus allowing lithospheric plates to move over it. The lowest subdivision is the transition zone. This is also where mineral phase changes occur to transform olivine to spinel.

[sdfghj]

Thank you

[LP]

Happy to help you