How and why earthquakes strike in the heartland; the role of sleep in strengthening memories; profile of marine geologist Sang-Mook Lee; and evolutionary evidence of the creatures that evolved into primates.

Using new data from cave stalagmites and the Mississippi riverbed to understand how and why earthquakes strike in the heartland; the crucial role sleep plays in strengthening memories and facilitating learning; a profile of marine geologist Sang-Mook Lee; paleontologist Jonathan Bloch, who thinks that tiny bones embedded in limestone may be the evolutionary evidence of the creatures that evolved into primates.