Question

why is it difficult to study the structure of earth

Answer 1

It is difficult to study the structure of the earth because the surface of the earth is round n that is why we fell difficult to study
In easy language it is difficult to fix the surface of the earth on a single sheet of paper

hope it helps u

Answer 2

study of structure of earth is difficult since we are not having accurate  knowledge about earth's interior. It was said that interior of earth is in molten state with high temperature and pressure. But now we came to see the latest finding that interior is filled with water in solid state