Abstract Sunset Crater, about 15 mi (25 km) north of Flagstaff, Arizona (Fig. 1), is in the eastern part of the San Francisco volcanic field, on the southern margin of the Colorado Plateau. Access to the Sunset Crater National Monument is by Forest Road 545, an all-weather road off of U.S. 89. Included within the boundaries of the monument are the scoria cone of Sunset Crater and most of one of its associated lava flows, the Bonito flow. Another lava flow associated with Sunset Crater, the Kana-a flow, occurs in the Coconino National Forest east of the monument. Hiking is prohibited on Sunset Crater scoria cone, and collection of specimens is not permitted within the boundaries of the national monument. Topographic maps published by the U.S. Geological Survey that cover the monument and surrounding area are the Sunset Crater East, Sunset Crater West, O’Leary Peak, and Strawberry Crater quadrangles of the 7%-minute series. The geology of the area is shown by Moore and Wolfe (1976).

ABSTRACT Every astronaut who walked on the Moon trained in Flagstaff, Arizona. In the early 1960s, scientists at the newly formed United States Geological Survey (USGS) Branch of Astrogeology led this training, teaching geologic principles and field techniques to the astronaut crews. USGS scientists and engineers also developed and tested scientific instrument prototypes, and communication and transportation technologies that would aid in lunar exploration. Astronomers and cartographers based at the USGS and Lowell Observatory, using telescopes at Lowell Observatory and the U.S. Naval Observatory, also played a key role, preparing lunar navigation charts and landing site maps. This historical and educational field trip will take participants along a historical path to some of the key sites where the Apollo astronauts trained. Field trip participants will see: (1) Grover , the geologic rover simulator on which the Apollo astronauts trained, which is on display at the USGS Astrogeology Science Center; (2) telescopes at Lowell Observatory used to map the lunar surface, as well as some of the original airbrushed maps; (3) the Bonito Lava Flow training area at Sunset Crater Volcano National Monument; (4) the Cinder Lake crater field, which was created in 1967 to simulate the lunar landscape for training astronauts and testing equipment; and (5) Meteor Crater, the best-preserved exposed impact crater on Earth. During this field trip we celebrate the 50th anniversary of one of the most remarkable events and most significant achievements in the history of humankind. We hope that the sites we visit will connect participants with the experiences of the astronauts and the excitement and inspiration of the origins of human space exploration. We also hope to communicate the historical significance of these sites, facilitate continued visitation of the sites (e.g., through class field trips), and educate the broader scientific and science education communities about the role that Flagstaff scientists and engineers played in the Apollo expeditions to the Moon.

ABSTRACT The San Francisco volcanic field stretches from Williams, Arizona, in the west, to northeast of Flagstaff, Arizona, on the east. Within the ~5000 km 2 area, more than 600 volcanoes are primarily monogenetic and basaltic, but silicic stratovolcanoes and domes are present as well. This field guide focuses on five broadly basaltic cones (Government Prairie vent, Red Mountain, SP Crater, Colton Crater, and Sunset Crater) and two silicic volcanoes (Kendrick Peak and San Francisco Mountain) in the field, with an emphasis on the different kinds of volcanic activity represented and the petrological variations. Hazards assessment indicates that is it possible for future eruptions to affect Flagstaff, but the probability is low. As information in this guide indicates, hazard assessments need to be improved to encompass a wide range of eruption types, and additional data are needed to improve models of the rate of volcanic activity and how the locus of activity has shifted over time.

Abstract The San Francisco Volcanic Field, located in northeastern Arizona, is host to over 600 volcanoes. These volcanoes began erupting approximately 6 million years ago in the western portion of the field and through time, the locus of activity has migrated eastward. Eruptive products range from basalt to rhyolite, with basalt dominant. Pleistocene vents include Merriam Crater and two associated cinder cones as well as The Sproul, a spatter rampart. One, or several, of these vents produced the Grand Falls flow which spilled over into the Little Colorado River gorge and flowed both up and downstream. Lava filled the canyon producing a dam and continued to flow ~ 1 km beyond the eastern rim. This changed the course of the river creating the waterfall at Grand Falls. Quaternary volcanism began as a fissure eruption that culminated with the building of Sunset Crater cinder cone. The eruption, which produced a blanket of tephra and two lava flows, was most certainly witnessed by the ancestors of the Pueblo Indians and had a dramatic impact on their lives. The eruption may have caused a shift in population to places such as Wupatki, 30 km to the north, where farming in the arid climate may have been temporarily enhanced by a thin layer of ash that acted as a water-retaining mulch. Melts that produced these dominantly basaltic cinder cones were derived by variable amounts of partial melting of an oceanic island basalt–like mantle source that underwent differing degrees of contamination from the lower crust. Subsequent fractional crystallization of olivine ° clinopyroxene further modified these melts. Discrete packets of these melts ascended rapidly to produce short-lived volcanic events in the eastern San Francisco Volcanic Field. The purpose of this field trip is to examine these young cinder cones and their eruptive products in an effort to understand the origin of the eruptions as well as the effects they had on the physiography and native inhabitants of the area.

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.