At Earth's surface, iron melts at 1250 K, and the temperature at Earth's core is approximately 5000 K. Which of these statements correctly characterizes iron in Earth's core?
A) Clearly, Earth's iron core is completely molten.
B) Because the melting temperature of iron depends also on the pressure to which it is subjected, it turns out that Earth's iron core is completely solid.
C) Because the pressure and temperature both vary with depth, it turns out that only the inner part of Earth's iron core is solid. This is surrounded by a liquid iron outer core.
D) Because the pressure and temperature both vary with depth, it turns out that only the inner part of Earth's iron core is molten. This is surrounded by a solid iron outer core.

Question

Quizplus · Accepted Answer

The pressure and temperature inside the Earth vary with depth, leading to a solid inner core surrounded by a liquid outer core. This is because the high pressure increases the melting point of iron, allowing the inner core to remain solid despite the high temperatures.

At Earth's Surface, Iron Melts at 1250 K, and the Temperature