<p>An unusual type of encrusted bubble froth accumulated within hyperthermophile biofilms along the waterline and splash zones of the Dewar Creek geothermal spring in southeastern British Columbia area of the Canadian Cordillera. Two tiers of adjoined bubbles resulted as the froth was progressively encrusted on the unconsolidated bottom sediment and an overlying crust. The calcium carbonate phase of the encrusted bubbles remains uncertain, but the depositional environment of the sediments accumulated along the geothermal spring includes innumerable amorphous calcium carbonate (ACC) spheroids, many with partial to complete transformation into larger calcite spherules. This depositional environment would be consistent with ACC nanoparticles precipitated on the bubble surfaces. Rapidly nucleated ACC or other calcium carbonate nanoparticles were responsive to electrostatic forces and resulted in their monodispersal on the 0.5 to 1.5&#xa0;µm diameter bubble surfaces. The nanoparticles were mobilized downward toward the basal attachment area of each bubble, resulting in a circular rim of nanoparticles at the top surface of the bubble. This process formed a circular zone without nanoparticles as the join site for the attachment of an overlying bubble and a nonoccluded conduit for connectivity between the gaseous interiors of the adjacent bubbles. Upon the removal of the protective biofilm cover, gas migrated upward between the interiors of the adjoined bubbles and outward into the water, bursting the upper tier bubbles. Infilling of the bubble interiors with water prevented collapse and complete obliteration. The fragmentary basal portions of the burst upper bubbles were preserved as bell-shaped fluid escape structures attached to the intact portions of the underlying encrusted bubbles. These fragile bell-shaped burst-nanobubble structures have not been previously documented in other hot spring deposits.</p>