Select the correct answer. Which layer of Earth is the densest and why is that so? A. The outer core is densest due to gravitational compression. B. The outer core is densest due to generation of radiogenic heat. C. The outer core is densest due to accretion. D. The inner core is densest due to gravitational compression. E. The inner core is densest due to generation of radiogenic heat.

The correct answer is D. The inner core is densest due to gravitational compression. The inner core of Earth, primarily composed of iron and nickel, reaches extremely high densities because of the immense pressure exerted by the layers above it. As you go deeper into the Earth, gravitational forces compress materials, increasing their density and resulting in the inner core being the heaviest layer. If you’re curious about Earth’s structure, the inner core is actually solid despite the intense heat, and it rotates faster than the rest of the planet! This contributes to our planet’s magnetic field through the dynamo effect, where the movement of molten iron in the outer core generates electric currents and, subsequently, the magnetic field we live in.