Which of the following statements best explains why the inner core of the Earth remains solid, despite temperatures being similar to or even higher than the outer core?
Show answer & explanation
Correct answer: B
Explanation
Solution: The correct answer is The gravitational pull at Earth's center compresses the inner core, raising its melting point beyond ambient temperature.
Explanation:
☛ The Earth's inner core experiences extremely high temperatures, ranging approximately from 5,000°C to 6,000°C, which is comparable to the surface of the Sun.
☛ Despite these extreme temperatures, the inner core remains solid due to the immense confining pressure exerted by the weight of all overlying layers (around 3.3 to 3.6 million atmospheres).
☛ Under such tremendous pressure, the melting point of the iron-nickel alloy increases significantly above the actual ambient temperature, preventing the atoms from flowing as a liquid.
☛ In the outer core, the pressure is not high enough to raise the melting point above the prevailing temperature, allowing it to remain in a liquid state.
Extra Exam-Relevant Facts:
☛ Core Composition: The Earth's core is primarily composed of Nickel (Ni) and Iron (Fe), often referred to as the NIFE layer.
☛ Earth's Magnetic Field: The convection of liquid iron in the outer core generates electric currents, producing Earth's magnetic field via the geodynamo effect.
☛ Lehmann Discontinuity: The boundary separating the liquid outer core from the solid inner core is known as the Lehmann Discontinuity.
☛ Gutenberg Discontinuity: The boundary located at a depth of about 2,900 km between the lower mantle and the outer core is called the Gutenberg Discontinuity.
Important One-Liners for Upcoming Exams:
☛ What is the boundary separating the outer core and inner core called? → Lehmann Discontinuity
☛ Which layer of Earth's interior is in a completely molten (liquid) state? → Outer Core
☛ Which type of seismic waves cannot pass through the Earth's outer core? → S-waves (Secondary waves)
☛ What is the boundary between the Earth's mantle and the outer core called? → Gutenberg Discontinuity
☛ Which Danish seismologist discovered the existence of Earth's solid inner core in 1936? → Inge Lehmann