1.   At even greater depths, the rock may give way to a metallic core.

2.   Earthquakes occur when the rocks finally give way, releasing accumulated stress.

3.   North of the Arizona border, the volcanic rock gives way to soft sand.

4.   The tumbled rocks give scant clue into the glory that once was Rome.

5.   Yet in many other ways, all four rocks give the appearance of being volcanic.

6.   Yet, all four rocks give the appearance of being volcanic.

7.   Archaeologists examining the core will look for places where the rock gives way to ancient earth containing fossils, and then excavate the sites where the samples were taken.