Working for the U.S. Geological Survey I get to measure time for a living. The technical term for a geologic timekeeper is a geochronologist. Have you ever wondered, as you drove down a mountain road, what the age of the rocks are as they passed by your windshield? Strange as it seems, I always wonder about this, and as a geochronologist, I get to actually answer this question because — I date rocks.

My boyhood home was in Niagara Falls, NY. There's a pretty famous waterfall there, and I've seen it thousands of times. As you stand next to Niagara Falls, you hear the thunderous roar of cascading water hurtling over the brink and you are covered in fine, cool mist. Looking to the north, you can see the deep gorge that the river has gouged over time. It was in these moments of awe, next to the mighty Niagara, that I started to wonder about geologic time. On visit after visit I thought to myself, "How old are the rocks here? How long did the river take to carve this gorge? Why are there marine fossils in the limestone and sandstone of the Niagara gorge, when there isn't an ocean nearby?"

I am not alone in needing answers to scientific questions. Many years before I was born, a far more inquisitive and adventurous soul was born in Mt. Morris, NY, just 60 miles as a crow flies from Niagara Falls. This person was John Wesley Powell. Powell's early years were filled with various river trips throughout the Midwest, attending multiple colleges, and feeding a restless nature and a deep interest in the natural sciences. After serving in the Union Army through the Civil War, he turned his attention to the scientific discovery of the American west.

On May 24, 1869, 150 years ago, Powell and his team started their expedition down the Green and Colorado Rivers. As each mile floated by, Powell was filled with questions, and undoubtedly, many of them revolved around a sense of time. How long would the trip take? How old are these rocks? How long did the river take to carve the labyrinth of these magnificent sandstone canyons? To be sure, he had far more questions than he had answers. Powell may not have been able to answer his many questions, but he had the vision to know that over time, those following in the wake of his boats down those same khaki colored rivers, would solve his queries, and at the same time, develop many more questions of their own.

That's what science is. Asking far more questions than can be answered. John Wesley Powell was a pivotal cornerstone (pun intended) in the early direction of the USGS as its second Director. For two weeks on the Colorado River, I will get the humbling opportunity to experience the same camaraderie, emotions, excitement, and wonderment that Powell and his men did 150 years ago. I will think about time, about Powell's time, my place in time, the vastness of geologic time, and just as Powell probably did, when is dinner time?