On which continent did the aztecs live?

The covers all of earth like a thin shell,but it is not a solid sheet of material.it is broken up into several large sections and many smaller ones. fill in the blank.

Ascientist makes a map using gis. one layer is an aerial photograph of farmland. other layers show water level changes and how crop cover has changed over time. what might the scientist be studying?

Which of the following is the unit of measurement used to describe the severity of an earth quake? velocity, magnitude, volume, density.