pumice Betydning & definition

Eksempler på pumice

• Concentrations of pumice clasts towards the base form trains of clasts that are traceable along the length of outcrops.

• Concentrations of accretionary lapilli and diffuse trains of small pumices define bedding in this thick ash bed.

• For selected ignimbrites, sanidine crystals were taken from fresh, unaltered pumice lapilli.

• Due to incomplete exposures, the dispersal characteristics of most pumice fallout deposits are poorly constrained.

• Widely dispersed plinian-type pumice fall deposits and ignimbrite are characteristic products of both explosive cycles.

• Lithic- and pumice-rich horizons may mark separate eruptive events.

• The presence of banded pumice near the top defines a compositional zonation of the ignimbrite.

• These tuffs are all considered to be ash flow deposits because they are unbedded and contain well-developed eutaxitic foliation and pumice pseudomorphs locally.