GEOLOGY

Detailed explanation-1: -Scientists discovered that Earth’s outer core is liquid by observing seismic waves . P waves travel through solid and liquid, but S waves do not travel through liquid.

Detailed explanation-2: -Scientist learned that the outer core is liquid by analyzing earthquake waves. The inner core is a dense ball of solid iron crystals.

Detailed explanation-3: -When P-waves strike the outer core, however, they bend downward when traveling through the outer core and bend again when they leave. This indicates that P-waves slow down in the outer core, suggesting that this layer has a significantly different composition from the mantle and may actually be liquid.

Detailed explanation-4: -P waves are detected on the opposite side of the Earth. Refractions between layers cause two shadow zones, where no P waves are detected – the size and positions of these shadow zones indicate there is a solid inner core.

Detailed explanation-5: -By tracking seismic waves, scientists have learned what makes up the planet’s interior (figure 2). P-waves slow down at the mantle core boundary, so we know the outer core is less rigid than the mantle. S-waves disappear at the mantle core boundary, so the outer core is liquid.