Both lie in a region that has been stretched, or extended, almost 100 percent from its original width in the last 10 million years. Evidences of this extension are massive fault block mountains such as Steens and Hart Mountains, with intervening basins containing features such as the Alvord Desert and Lake Abert.
Intense volcanic and hot-spring activity has produced fine-grained gold deposits and jasperoids that are prized by rock hounds.
