According to the present interpretation, the trees from high mountains, those from intermediate hills, and those from tropical lowlands all were washed together into low swamps and lakes by streams and rivers. Thus trees of great variety were mixed together in the basalt beds of Ginkgo Petrified Forest State Park. The region now varies in elevation from about 1000 feet to 3000 feet above sea level. A number of miles to the west, the Cascade Mountains rise several thousand feet higher. Presently the area experiences cold winters and hot summers.
Rainfall is light.
The number of indigenous tree species is somewhat limited. If all these many kinds of fossil trees lived together originally in this area, the range in elevation must previously have been much greater than it is now, and the lower areas must have experienced tropical growing conditions. This interpretation is not entirely satisfactory. There is no place in the world today where so great a variety of tree species grows in such close proximity. The length and diameter of the petrified logs would require more than small streams to move such trees down to the lowlands.