How do we know that the earth is not the same composition all the way through?

Question

a.seismic waves do not arrive uniformly all over the earth.

b.there are two types of seismic waves,s- and p-waves.

c.where the mantle is exposed ,it looks very different.

d.seismic waves attenuate with distance.

Answer 1

c

Where bedrock is exposed in different geographical areas the rock is a different type.

Also, many years of drilling for oil and water, core samples have been extracted which show that rock differs at different depths.

Many areas that have thrust faults dating back millions of years, showing rock from deep within the earth have differing composition.

We haven't drilled more than a few miles into the earth, but what we do know from the scratches, the composition differs as you get deeper.

Answer 2

a