The Colorado River may be taken for granted by millions of people, but many researchers are intrigued by its evolution and other natural attributes, and they are trying to get more details about its origins and evolutionary changes.

The river is credited with carving out the Grand Canyon, and creating important habitats all the way to the Sea of Cortez. But in terms of geologic time, scientists say the Colorado is a relatively young river.

John Spencer is a senior geologist with the Arizona Geological Survey, and Phil Pearthree is research geologist with the group.

Both joined AZ Illustrated Nature to talk a bit about their studies, which include information about the development of the Colorado and other rivers whose headwaters are in high mountainous areas.

"We have good evidence, in the case of the Colorado, that it's developed geologically really recently," Pearthree said. "Five million years ago or six million years ago, it didn't exist like its modern form so part of the fun research that Jon and I have been involved in is to find evidence, figure out how the river developed."

And they believe there have been important changes in Arizona's topography that have impacted the Colorado River. For instance, at one time the southern part of the state was generally much higher than the northern part but that has been reversed.

"The arrival of the Colorado River in a way reflects the adjustment of river systems to a changing landscape," Spencer said.

Spencer said there is much more to be learned about Arizona's environmental evolution, including the existence of marine fossils in our sediment.

He said he theorizes that these fossils ended up in Arizona due to the movement of birds from other regions.