Figure 2. Around 1,100 million years ago southwestern North America was apparently in the middle of the supercontinent, Rodinia, and may have been adjacent to Gondwanaland, which eventually became Australia and Antarctica. (Source: R. Blakey, Northern Arizona University, Paleogeography of the Southwestern U.S.: http://jan.ucc.nau.edu/~rcb7/paleogeogwus.html