How can an older rock layer appear on top of a younger rock layer?

Select the statements below that correctly describe where earth's three most abundant elements (iron, oxygen, and silica) are located. choose one or more: the majority of iron is located in the core. silica is abundant in the mantle and crust. the majority of oxygen is located in the crust and mantle. oxygen is only located in earth's atmosphere and is not found anywhere inside earth. silica is abundant in the crust, mantle, and core. no iron is located in the crust.