It used to be a joke in the Geological Surveys of the Soviet Union that they employed so many thousands of geologists that the entire USSR could be mapped in a few years if they all linked hands and walked from east to west. Geophysicists are trying for something similar to map the mantle underlying the USA in 3-D. The USArray involves 400 portable seismometers, currently spread out at 10 km intervals in the western States, is intended to act like a fly’s eye in monitoring arrival times of seismic waves from worldwide earthquakes. The plan is to steadily move the array eastwards until by 2013 it has reached the Atlantic coast. From that data the geophysicist hope vastly to improve the resolution of seismic tomographic images of the deep Earth (see Kerr, R.A. 2009. Scoping out unseen forces shaping North America. Science, v. 325, p. 1620-1621). Yep, they are definitely going for a high ‘Wow factor’ rating. Yet is seems that there are other expletives floating around as the strangely knobbly and discontinuous architecture that is emerging from early data processing refuses to fit many simple hypotheses being tested.