It is widely accepted that the Earth’s interior is composed of several layers: the crust, the mantle and the core. Since the crust is readily accessible, scientists have been able to perform hands-on experiments to determine its composition; studies on the more distant mantle and core have more limited opportunities samples, so scientists also rely on analyses of seismic waves and gravity, as well as magnetic studies.
Measuring Seismic Waves
It is impossible to drill to the center of the earth, so scientists rely on indirect observations of matter lying below the surface through use of seismic waves and their knowledge of how these waves travel during and after an earthquake.
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he outer core of the Earth is a liquid layer about 2,260 kilometers thick. It is made of iron and nickel. This is above the Earth's solid inner core and below the mantle. Its outer boundary is 2,890 km (1,800 mi) beneath the Earth's surface.
