Walker first George P L coauthors Edgardo Ca n Tapia Emilio Herrero Bervera title Origin of vesicle layering and double imbrication by endogenous growth in the Birkett basalt flow Columbia river plateau journal Journal of Volcanology and Geothermal Research volume 88 issue pages 15 28 publisher date 1999 url jstor issn doi i d accessdate 28 August 2011 Cite journal last