Lapilli

Under lapilli ( Italian for " stones " ) are a pea to a walnut sized ( 2-64 mm ) pyroclastic referred to in volcanology, which are promoted in an explosive volcanic eruption. The lapilli, together with the volcanic ash (<2 mm), the bombs ( > 64 mm, rounded, originally melted) and the volcanic blocks ( > 64 mm, angular, already at the time of ejection ) the pyroclastic sediments ( also tephra called when unconsolidated ) or pyroclastic rocks (if solidified ).

Characteristics

The term lapilli so designated only one grain size and is no genetic designation. Lapilli can therefore consist of lava, slag, remnants of old chimney fillings or xenoliths. Lapilli can pyroclastic fall or flow deposits form. A pyroclastic rock composed predominantly ( > 75 %) of lapilli, Lapillistein is called. A lapilli - tuff is a pyroclastic rock on the other hand, which contains less than 25% of bombs and blocks and more than 75 % lapilli and ash. Overall, however, these deposits must consist of more than 75 % of pyroclastics.

Accretionary lapilli are lapilligroße lumps of ash fragments that are encouraged in phreatomagmatic explosions. They arise when the ash particles accumulate around a "core" around. This nucleus may be, for example, a solid particle, as well as a drop of water. On the latter, they are created when raindrops fall through the eruption column and thereby ash accumulates around the drops around. Accretionary lapilli occur in both pyroclastic fall as well as pyroclastic flow deposits.