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?

Answer 1

The differences in the state of the core (liquid outer core and solid inner core) are primarily due to temperature and pressure conditions at different depths within the Earth.

1. Temperature: The temperature in the outer core is extremely high, ranging from about 4,000 to 6,000 degrees Celsius (7,200 to 10,800 degrees Fahrenheit). At these temperatures, the iron and nickel are in a liquid state due to the thermal energy that overcomes the metallic bonding forces.

2. Pressure: As you move deeper into the Earth, the pressure increases significantly. In the inner core, the pressure is immense (estimated at over 3 million atmospheres), which affects the state of the material. Even though the temperature in the inner core is similar to that in the outer core, the high pressure forces the iron and nickel into a solid state. The immense pressure raises the melting point of these metals, preventing them from melting despite the high temperatures.

In summary, the combination of high temperatures that create a liquid state in the outer core and the extremely high pressures in the inner core that solidify the metal results in the observed differences between the two layers of Earth's core.