Basaltic ring structures of the Columbia Plateau

Abstract

Research Article| September 01, 1978 Basaltic ring structures of the Columbia Plateau CARROLL ANN HODGES CARROLL ANN HODGES 1U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information CARROLL ANN HODGES 1U.S. Geological Survey, Menlo Park, California 94025 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1978) 89 (9): 1281–1289. https://doi.org/10.1130/0016-7606(1978)89<1281:BRSOTC>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation CARROLL ANN HODGES; Basaltic ring structures of the Columbia Plateau. GSA Bulletin 1978;; 89 (9): 1281–1289. doi: https://doi.org/10.1130/0016-7606(1978)89<1281:BRSOTC>2.0.CO;2 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 SocietyGSA Bulletin Search Advanced Search Abstract Circular structures, defined by arcuate, concentric ridges and scarps that surround hills, mesas, or crater-like depressions, are localized in an exceptionally thick section of the Roza Member of the Yakima Basalt on the Columbia Plateau. Autointrusive dikes are conspicuous in most ridge segments. Palagonite discovered in a few central hills appears genetically related to the ring structures and suggests an origin involving interaction of water and lava. The dikes intruded a crust about 30 m thick, however, so that substantial cooling must have occurred prior to formation of the rings.A plausible explanation for these unusual features may hinge on the disruption of drainage that occurred as a result of the voluminous basalt extrusion. If, after partial cooling, the molten interior of this thick ponded Roza flow were intersected by a rising ground-water table, rapidly accumulating volatiles could have caused explosive venting as well as doming and cracking of the crust, with concurrent emplacement of granulated sideromelane (later palagonitized) and tephra in craters and fractures. Subsidence of the crust after initial venting could have permitted intrusion of melt into fractures predominantly concentric to the focus of pressure release. Subsequent catastrophic erosion by the Missoula floods effectively removed most of the surficial clues to original structure and morphology, leaving the roots of these enigmatic features partly exposed. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.