|
agglomerate. Welded or non-welded coarse-grained deposit formed mainly of juvenile pyroclasts (typically spatter, scoria, pumice, or obsidian ‘bombs’ or lapilli) whose shapes and/or external surface textures indicate that they were partly fluidal during transport. Agglomerates can be deposited by pyroclastic density currents (p.61), by pyroclastic fall or ballistically. Those within ignimbrite sheets commonly contain subordinate lithic blocks, pumice lapilli and pumiceous ash, and grade into pumiceous ignimbrite and/or massive lithic breccia (p. 57). In powder technology, loosley bonded clusters or clumps of fine cohesive particles are referred to as ‘agglomerates’
agglomeration. Adherence and clustering together of ash particles to form agglomerations: i.e. loose or firm clumps, pellets and/or accretionary lapilli. Fine ash may agglomerate within an eruption plume or in a pyroclastic density current initially due to electrostatic effects or (when moist) surface tension effects, and the agglomerations may be rapidly cemented by precipitation of slats as water evaporates (p. 83).
agglutination. Very rapid, syn-depositional welding of hot, fluidal pyroclasts prior to burial by aggrading ignimbrite (p. 84). Agglutination resultsin a welded tuff in which former clast outlines are still visible (cf. coalescene in which they are not).
amalgamation. Inferred seamless joining of deposits from successive discrete depositional events to produce a single bed with ni trace of a hiatus (p. 95).
...
This 250-word extract was created in the absence of an abstract.
