Figure 4. Antler arc ploughs into western North America interrupting 100s of millions of years of passive sediment accumulation along the west coast and initiating the Antler Orogeny mountain-building episode in central Nevada. (Source: R. Blakey, Northern Arizona University, Paleogeography of the Southwestern U.S.: http://jan.ucc.nau.edu/~rcb7/paleogeogwus.html)