It traps energy from escaping into space!
The inner core is solid because it is made of very dense, or heavy, materials - like iron and nickel. Even though it is very hot, these materials don't "melt" very easily, so they stay solid. Also, pressure due to the weight of the mantle and crust, atoms are forced together as solid.
This are some of the things behind imperialism in Africa.
1) Need for resources,
2) Political competition
3) Technological advances
Economic factors were more of a driving force behind imperialism because the imperialists were in need for natural resources for them to improve their technology and their national pride.
C. on reserves
hope this helps
