Unless a series of sedimentary rock layers has been overturned, which layer is usually the oldest?

the layer on the top
the layer with the most minerals
the layer with the most fossils
the layer on the bottom
the igneous intrusion (dike)

The layer on the bottom generally. 

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