Effects of topography on pyroclastic density current runout and formation of coignimbrites

Research Article| December 01, 2011 Effects of topography on pyroclastic density current runout and formation of coignimbrites Benjamin J. Andrews; Benjamin J. Andrews 1Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, 1000 Constitution Avenue Northwest, Washington, D.C. 20004, USA Search for other works by this author on: GSW Google Scholar Michael Manga Michael Manga 2Department of Earth and Planetary Science, University of California−Berkeley, 307 McCone Hall, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Benjamin J. Andrews 1Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, 1000 Constitution Avenue Northwest, Washington, D.C. 20004, USA Michael Manga 2Department of Earth and Planetary Science, University of California−Berkeley, 307 McCone Hall, Berkeley, California 94720, USA Publisher: Geological Society of America Received: 03 Mar 2011 Revision Received: 21 Jun 2011 Accepted: 27 Jun 2011 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2011 Geological Society of America Geology (2011) 39 (12): 1099–1102. https://doi.org/10.1130/G32226.1 Article history Received: 03 Mar 2011 Revision Received: 21 Jun 2011 Accepted: 27 Jun 2011 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Benjamin J. Andrews, Michael Manga; Effects of topography on pyroclastic density current runout and formation of coignimbrites. Geology 2011;; 39 (12): 1099–1102. doi: https://doi.org/10.1130/G32226.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Laboratory experiments of dilute mixtures of warm talc powder in air simulate dilute pyroclastic density currents (PDCs) and show the effects of topography on current runout, buoyancy reversal, and liftoff into buoyant plumes. The densimetric and thermal Richardson, Froude, Stokes, and settling numbers for our experiments match those of natural PDCs. The laboratory currents are fully turbulent, although the experiments have lower Reynolds numbers than PDCs. In sum, our experiments are dynamically similar to natural currents. Comparisons of currents traversing flat topography or encountering barriers show that runout distance is not significantly reduced for currents that traverse barriers with height <1.5 times the current thickness, but currents do not pass taller barriers. Buoyancy reversals occur in most currents, resulting in liftoff and generation of a buoyant plume. Liftoff occurs near the maximum runout distance for currents traveling over flat topography, but is focused near or above barriers for currents that encounter barriers. Notably, plume formation above barriers can result in reversal of flow direction downstream of the obstruction as portions of the current flow back and feed the rising plume. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.