Diferència entre revisions de la pàgina «Lapil·li»

101 bytes afegits ,  fa 3 anys
== Formació==
[[File:Accretionary Lapilli - geograph.org.uk - 831917850.jpg|thumb|dretaesquerra|<center>Lapil·li de creixement del [[MesoproterozoicFuerteventura]], [[Stac Fada MemberEspanya]] del [[Torridonià]].</center>]]
Lapilli are spheroid-, teardrop-, dumbbell- or button-shaped droplets of molten or semi-molten [[lava]] ejected from a volcanic eruption that fall to earth while still at least partially molten. These granules are not accretionary, but instead the direct result of liquid rock cooling as it travels through the air.
=== Lapil·li de creixement ===
[[File:Accretionary Lapilli - geograph.org.uk - 831917.jpg|thumb|dreta|<center>Lapil·li de creixement del [[Mesoproterozoic]] [[Stac Fada Member]] del [[Torridonià]].</center>]]
Rounded [[tephra]] balls are called ''accretionary lapilli'' if they consist of [[volcanic ash]] particles. Accretionary lapilli are formed in an eruption column or cloud by moisture or electrostatic forces, with the volcanic ash nucleating on some object and then accreting to it in layers before the accretionary lapillus falls from the cloud. Accretionary lapilli are like volcanic hailstones that form by the addition of concentric layers of moist ash around a central nucleus.