Hundreds of years for succession may seem long in human terms, but in Earth's history it is the mere blink of an eye. The changes in communities that occur as the geology and climate of the earth alter are called floristic changes. They can take thousands, or even millions, of years. The eastern side of Washington, which today largely lacks forests, was once covered by forest. Between 15 and 20 million years ago, eastern Washington had a climate that was much wetter and warmer, and the landscape was forested. Fossil remnants of this forest can be seen at Ginkgo State Park, where the trunks of ancient ginkgo (Ginkgo biloba), hickory (Carya species), and Douglas fir (Pseudotsuga menziesii) have been petrified in lava. As the global climate changed, warming the interior of North America, and the Cascade Mountains began to uplift about 7 million years ago, eastern Washington became much drier. The vast moist forests that once covered central Washington began to disappear, and they were replaced by the scrubby grasslands that we find today east of the Cascade Mountains. Eastern Washington had undergone floristic change.