Coal deposits formed in a swampy coastal environment. Many impacts of older mountain building events were overprinted and re-mineralized by the Laramide orogeny, 89 to 43 million years ago, which built the Rocky Mountains. Volcanic activity, magmatism and mineralization shifted eastward into Arizona.
Why did Arizona become a desert?
Cool ocean temperatures, a mountain range and a prevailing west-to-east wind make Arizona the desert it is!
How long has Arizona been a desert?
Although brittlebush and saguaro returned to Arizona soon after the beginning of the present interglacial (the Holocene) about 11,000 years ago, the Sonoran Desert did not re-form until about 9000 years ago, as the last displaced woodland plants retreated upslope.