ABSTRACT The Grand Canyon is perhaps our planet’s most widely recognized and single most important geologic landform. The goals for this trip are to give participants an understanding of the canyon’s formation and its dynamic hydrologic system. While our destination is clear, the journey will also provide opportunities to discuss Arizona’s larger geologic setting within the Basin and Range, Transition Zone, and Colorado Plateau physiographic provinces. Stops and discussions will include: (1) geologic setting and groundwater environment of the Phoenix basin; (2) Cenozoic landscape development of the Transition Zone; (3) Montezuma Well, a unique arid-land spring contained within a travertine mound; (4) ascent of the Mogollon Rim, the state’s second largest landform and entryway to the Colorado Plateau; (5) the San Francisco Volcanic Field and surrounding volcanic features, including Sunset Crater, a late Holocene scoria cone; and (6) multiple stops in Grand Canyon National Park to discuss its varied geology. The principal focus here will be on evolving concepts of the canyon’s formation since the time of John Wesley Powell, including the flurry of research results proffered in the past 20 years. Participants will walk the Trail of Time, Earth’s largest man-made geologic exhibit at over 2 km. Another equally important discussion will cover the modern hydrologic system of the canyon, which yields a tenuous supply of potable water from a single inner-canyon spring for over six million annual visitors and 2,500 full-time residents. The National Park Service has prioritized the replacement of the Trans-Canyon Waterline due to climate change concerns.

Abstract This walking tour will consider local geology, touch on local history, and focus on the building stones used in downtown Dayton. Building stones and construction materials used along Main Street are the main interest. Special attention will be paid to “Dayton’s own,” the Dayton limestone—a stone considered by State Geologist Edward Orton in the second half of the nineteenth century ( Orton, 1870 , 1893 ) as one of Ohio’s finest building stones. The Dayton Formation (Dayton limestone) was used extensively as a building stone in the Dayton area (and farther afield) during the nineteenth and early years of the twentieth centuries during the growth of Dayton. Perhaps the zenith of the Dayton limestone building-stone industry is characterized by the Old Courthouse (1850), an important building in the Greek-Revival architectural-style that saw the use of Dayton limestone not only for the exterior of the building but also, unusually, and perhaps with a little too much enthusiasm, for slabs of limestone for the roof. This building has much local historical significance— both Presidents Abraham Lincoln and John F. Kennedy addressed the public from its steps. Dayton limestone was used for the commemorative stone from the State of Ohio, installed in 1850, inside the Washington Memorial, Washington, D.C., and for part of the “Ohio House” built for the International Exhibition at Fairmount Park, Philadelphia, Pennsylvania, commemorating the centennial of the signing of the Declaration of Independence in 1876. Use of the stone is also documented in Cincinnati, Columbus, and Chicago. Recent developments along East Monument Avenue and Patterson Boulevard— RiverScape and the Patterson Boulevard canal walk—as well as some of the buildings, will be discussed. The “Great Dayton Flood” of 1913 probably resulted in excess of four hundred deaths along the Great Miami River valley and its watershed. The Miami Conservancy District oversees the flood-prevention scheme that developed after the 1913 flood; their headquarters are housed in a building that overlooks the Great Miami River in downtown Dayton. Flood-prevention modifications to the Great Miami River can be seen adjacent to downtown.