ABSTRACT Rampart craters are omnipresent features on volatile-rich solid planetary surfaces. This raises the question whether, and how many, rampart craters are present on Earth. We reviewed the terrestrial impact crater record with regard to possible rampart morphologies and present detailed morphological analyses of these terrestrial craters here. Our results show that the Ries crater in Germany, Bosumtwi crater in Ghana, Tenoumer crater in Mauritania, Lonar crater in India, and Meteor crater in the United States are terrestrial rampart craters. The Ries and Bosumtwi craters can be classified as double-layer ejecta (DLE) craters, whereas Tenoumer, Lonar, and Meteor craters can be classified as single-layer ejecta (SLE) craters. Tenoumer and Meteor craters show rampart as well as common lunar-like ejecta characteristics within their ejecta blankets and, thus, appear to be hybrid craters. In addition, we discuss seven crater structures that show at least some morphological or lithological peculiarities that could provide evidence for possible ejecta ramparts. Considering the low number of terrestrial impact craters with well-preserved ejecta blankets, the relatively high proportion of rampart craters is astonishing. Obviously, the formation of layered or rampart craters is a common and not a rare process on Earth.

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 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 Arizona has a wide variety of geological features relevant to planetary geology. The “Holey Tour” is a 2 d field trip (Phoenix-Flagstaff-Phoenix) that introduces participants to crater forms (hence the “holes” of the tour), including a maar, karst sinkhole, pit crater, cinder-cone craters, a volcano-tectonic depression, and the classic impact structure Meteor Crater. The Apollo astronaut field training site near Flagstaff is examined, which includes a terrain that was artificially generated to simulate a cratered lunar surface. In addition, planetary volcanism is discussed with stops that include a shield volcano, composite cone, silicic dome, and cinder cones; considerations include key variables in volcanic morphology, such as lava composition and rates of effusion. The general geology of Arizona is discussed throughout the trip and includes parts of the Colorado Plateau, the Basin and Range Province, and the Central Highlands (also called the “transition” zone). The trip can be adapted to meet the needs of any group, from secondary school students to established planetary scientists. This field trip generally follows the GSA guide published in GSA Special Paper 483 (available at https://pubs.geoscienceworld.org/gsa ): Greeley, R., 2011, The “Holey Tour” planetary geology field trip, Arizona, in Garry, W.B., and Bleacher, J.E., eds., Analogs for Planetary Exploration: Geological Society of America Special Paper 483, p. 377–391, https://doi.org/10.1130/2011.2483(23) .