Publications
Filter Total Items: 2687
Hawaiian volcanic ash, an airborne fomite for nontuberculous mycobacteria
Nontuberculous mycobacteria (NTM) are environmentally acquired opportunistic pathogens that can cause chronic lung disease. Within the U.S., Hawai'i shows the highest prevalence rates of NTM lung infections. Here, we investigated a potential role for active volcanism at the Kīlauea Volcano located on Hawai'i Island in promoting NTM growth and diversity. We recovered NTM that are known to cause lun
Authors
Stephanie Dawrs, Ravleen Virdi, Grant Norton, Tamar Elias, Nabeeh Hasan, Schuyler Robinson, Jobel Matriz, L. Elaine Epperson, Cody Glickman, Sean Beagle, James L Crooks, Stephen T. Nelson, Edward Chan, David Damby, Michael Strong, Jennifer Honda
Overview of the Cenozoic geology of the northern Harrat Rahat volcanic field, Kingdom of Saudi Arabia
The Harrat Rahat volcanic field, located in the west-central part of the Kingdom of Saudi Arabia, is one of the larger Cenozoic harrats among the more than 17 harrats situated upon the Arabia Plate. The map plate contained herein shows, at a scale of 1:100,000, the mapped volcanic geology of northern Harrat Rahat, which consists of the northernmost one-fifth of Harrat Rahat. Northern Harrat Rahat
Authors
Joel E. Robinson, Drew T. Downs
Magnetotelluric investigation of northern Harrat Rahat, Kingdom of Saudi Arabia
Volcanism within the harrats (Arabic for “volcanic field”) of the Kingdom of Saudi Arabia includes at least one historical eruption occurring close to the holy city of Al Madīnah in 1256 C.E. As part of a volcanic- and seismic-hazard assessment of northern Harrat Rahat, magnetotelluric (MT) data were collected to investigate the structural setting of the area, the presence or absence of melt withi
Authors
Jared R. Peacock, Paul A. Bedrosian, Maher K. Al-Dhahry, Adel Shareef, Daniel W. Feucht, Cliff D. Taylor, Benjamin Bloss, Hani M. Zahran
Isotopic and geochemical evidence for the source of volcanism at Harrat Rahat, Kingdom of Saudi Arabia
Pleistocene and Holocene basalts, hawaiites, mugearites, benmoreites, and trachytes from the northern part of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia, were analyzed for Sr, Nd, Hf, and Pb isotopic compositions. Evolved trachytes with Mg number <0.1 (Mg# = Mg/[Mg+Fe2+], molar) have relatively radiogenic Sr isotopic compositions indicating that they were influenced by contamination
Authors
Vincent J.M. Salters, Afi Sachi-Kocher, Drew T. Downs, Mark E. Stelten, Thomas W. Sisson
Mantle origin and crustal differentiation of basalts and hawaiites of northern Harrat Rahat, Kingdom of Saudi Arabia
Quaternary volcanic rocks of northern Harrat Rahat, Kingdom of Saudi Arabia, are chiefly alkali basalts with subordinate transitional basalts, hawaiites, mugearites, benmoreites, and trachytes. Geochemical and isotopic results indicate that crystallization-differentiation, mixing, and cumulate reassimilation within the magmatic system produced most of its compositional diversity, with only minor i
Authors
Thomas W. Sisson, Drew T. Downs, Andrew T. Calvert, Hannah R. Dietterich, Gail A. Mahood, Vincent J.M. Salters, Mark E. Stelten, Jamal Shawali
Paleomagnetism of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia—Geologic unit correlations and geomagnetic cryptochron identifications
Paleomagnetic rock samples were collected from 173 drill sites in the Quaternary alkali basaltic volcanic field of northern Harrat Rahat, Kingdom of Saudi Arabia. Laboratory measurements on these samples established that lava flows and vent complexes—identified and mapped from field characteristics, rock types, and compositions as products of single or temporally close eruptions—typically record s
Authors
Duane E. Champion, Drew T. Downs, Mark E. Stelten, Joel E. Robinson, Thomas W. Sisson, Jamal Shawali, Khalid Hassan, Hani M. Zahran
Explosive trachyte eruptions from the Al Efairia volcanic center in northern Harrat Rahat, Kingdom of Saudi Arabia
Harrat Rahat is an alkali basalt, continental, intraplate volcanic field located within the central-western part of the Kingdom of Saudi Arabia. The northern quarter of Harrat Rahat contains evolved volcanic products that achieve trachyte compositions (>60 weight percent SiO2). Within the Al Efairia volcanic center, pyroclastic-flow and -surge deposits that reflect explosive trachyte volcanism (an
Authors
Drew T. Downs, Mark E. Stelten, Hannah R. Dietterich, Duane E. Champion, Gail A. Mahood, Thomas W. Sisson, Andrew T. Calvert, Jamal Shawali
The duration and characteristics of magmatic differentiation from basalt to trachyte within the Matan volcanic center, northern Harrat Rahat, Kingdom of Saudi Arabia
A fundamental goal of igneous petrology is to quantify the durations required to produce evolved magmas following influx of basalt into the crust. However, in many cases, complex field relations and (or) the presence of a long-lived magmatic system make it difficult to assess how basaltic inputs relate to more evolved magmas, therefore precluding calculation of meaningful timescales. Here we prese
Authors
Mark E. Stelten, Drew T. Downs, Hannah R. Dietterich, Gail A. Mahood, Andrew T. Calvert, Thomas W. Sisson, Molly R. Witter, Hani M. Zahran, Jamal Shawali
Lava flow emplacement in Harrat Rahat with implications for eruptions in mafic volcanic fields
Mafic volcanic fields are widespread, but few have erupted in historical times, providing limited observations of the magnitudes, dynamics, and timescales of lava flow emplacement in these settings. The Harrat Rahat volcanic field in western Saudi Arabia offers a good opportunity to study eruptions in such a setting, with a historical eruption in 1256 C.E. (654 in the year of the Hijra) and numero
Authors
Hannah R. Dietterich, Drew T. Downs, Mark E. Stelten
Eruptive history of northern Harrat Rahat—Volume, timing, and composition of volcanism over the past 1.2 million years
Harrat Rahat, one of several large, basalt-dominated volcanic fields in the western part of the Kingdom of Saudi Arabia, is a prime example of continental, intraplate volcanism. Excellent exposure makes this an outstanding site to investigate changing volcanic flux and composition through time. We present 93 40Ar/39Ar ages and 6 36Cl surface-exposure ages for volcanic deposits throughout northern
Authors
Mark E. Stelten, Drew T. Downs, Duane E. Champion, Hannah R. Dietterich, Andrew T. Calvert, Thomas W. Sisson, Gail A. Mahood, Hani M. Zahran
Eruptive history within the vicinity of Al Madīnah in northern Harrat Rahat, Kingdom of Saudi Arabia
The northernmost part of the Harrat Rahat volcanic field contains early Pleistocene to Holocene mafic eruptive products within the vicinity of the city of Al Madīnah, Kingdom of Saudi Arabia. A detailed geologic investigation into the eruptive history of a 570 square kilometer (km2) area covering Al Madīnah and the surrounding area has yielded 33 mapped Quaternary volcanic units consisting of lava
Authors
Drew T. Downs, Mark E. Stelten, Duane E. Champion, Hannah R. Dietterich, Khalid Hassan, Jamal Shawali
Cenozoic tectonics of the western Arabia Plate related to harrat magmatism near Al Madīnah, Kingdom of Saudi Arabia
Sprawling volcanic fields, or harrats, in western Saudi Arabia have been emplaced during the past 30 million years following effusions of flood basalts in Ethiopia and Yemen. Although broadly associated with volcanism in three rift valleys (Red Sea, Gulf of Aden, and East African Rift Zone) radiating from the Afar depression, harrat abundance on the Arabian Peninsula indicates that volcanism is di
Authors
Andrew T. Calvert, Thomas W. Sisson