* P-waves travel faster through denser materials: When P-waves travel through the Earth's mantle, they slow down slightly. This is because the mantle is primarily made of solid rock. However, when they reach the Earth's core, they speed up dramatically. This indicates that the core is much denser than the mantle.
* P-waves change direction at the core-mantle boundary: P-waves also change direction slightly as they pass from the mantle into the core. This bending of the waves, known as refraction, is another indication of a change in density and composition.
What these observations tell us:
* The core is much denser than the mantle: The speed increase of the P-waves tells us that the core must be made of something denser than the rocky mantle.
* The core is likely made of iron and nickel: The density and speed changes are consistent with a core composed primarily of iron and nickel, which are both very dense metals.
In summary: The speed and direction changes of P-waves as they travel through the Earth provide crucial clues about the composition of the core. They tell us that it is very dense and likely made of iron and nickel.
