The core of Earth is made out of iron and nickel. The outer core’s temperature is so hot that it melts the metal. The inner core is solid metal. What causes these differences? 1. The outer core is 2,300 km thick.
2. the inner core is solid by intense pressure of all its layers above it
3. the inner core has a cooler temperature allowing the metal to return solid
4. the inner core is made of different metal