Scientists collected evidence from to determine when rocks were laid down in layers, and they compared rocks and index fossils worldwide to organize the scale.

The answer is a because - is an direction

Generally travels west to east but often shifts to north and south

Because the earth is not round ,but it may seem round when viewed from ,our planet but true some points earth is not round was an oblate spheroid -a square that it squashed as globe however is not even a perfect oblate spheroid.in fact isaac newton's first proposed that earth was not perfectly round but it was an oblate spheroid instead.that mean a square that is squashed as its poles and swollen at the