The Geoshpere: core, mantle and crust

Watch some videos on Earth's layers,

 and take a look at some voluntary 3rd primary projects.

The Crust, The Mantle and The Core

How Scientists Know About These Layers

Then check out this video and a song on 

Latitude (parallels) and Longitude (meridians)

Lines of Latitude and Longitude (use Captions)
"Do You Know What Longitude/Latitude Means?" song