#lapilli

Lapilli, meaning ‘little stones’ in Latin, can have diverse origins, but the example shown on a photograph is more precisely called accretionary lapilli.

Accretionary lapilli form during a volcanic eruption in the ash cloud. When big volcanic eruption occurs, a volcano will blow a huge cloud into the atmosphere. Such cloud will contain massive boulders, smaller rocks, volcanic ash and gases etc. Rocks are heavy, so they fall back down fast, however, ash and gases do not. The most abundant and important in this process gas is a water vapour.

Mix fine ash and water vapour/steam together and what you get is an airborne mud. Water vapour sticks ash particles together, so as the huge turbulent ash cloud grows and mixes, more and more ash particles come together to form little balls (lapilli) which then rain down like hail once they get too heavy.

Desiderio, Passione, Pulsioni: C’è del fuoco dentro di noi

No, ancora non ce ne rendiamo conto. Siamo ancora troppo presi dalle “vibrazioni basse” che emanano le parole “lockdown” “distanziamento” “assembramento”. Invece noi siamo come una Fenice, che dentro arde, arde di passione da contatto carnale verso se stessa e verso il proprio partener (magari fuori regione, o addirittura all’estero), o magari semplicemente fuori comune. Quelle che ad un occhio…

new gemsona, first one I’ve made in almost a year wow

her name is lapilli and she is a fusion of three lapilli, which are very tiny gems. her third gemstone is on her navel. she’s about peridot’s waist height and her components are about as tall as peridot’s shoes. she’s kinda similar to entrapta. her weapon is a hand grenade and she enjoys destruction. in her notebook, she records results of her experiments, which usually involve explosions. she has escaped homeworld, but doesn’t align with any official rebel group.

Yr Arddu, North Wales.

Accretionary Lapilli

This photo is from an outcrop of the Erill Castell formation in the Spanish Pyrenees showing examples of accretionary lapilli. The rocks date back to 272 - 303ma to the Carboniferous - Permian boundary and are associated with the formation of the supercontinent Pangea.

The force of the colliding continents led to thickening of the continental crust and the growth of mountain ranges. This also caused the crust to thicken downwards by penetrating deep into the mantle, where increased temperatures caused the rocks to melt. This process produced large volumes of magma which began to rise towards the surface using faults and fractures as conduits. The magma pooled within chambers in the upper crust, later erupting to form volcanoes. Accretionary lapilli form during phreatomagmatic eruptions –where the magma comes into contact with either meteoric (water produced by precipitation) or seawater leading to a very explosive reaction! (the magma boils the water causing it to expand and turn into steam). This can occur due to the presence of crater lakes or from a volcano that has become shallowly submerged by seawater, and if you’re very unlucky it can be a combination of the two. This was the case in Santorini when Thera erupted, leading to the extinction of the Minoan civilisation.

The lapilli form either from the magma itself or as fragments of the original crater broken off during the eruption. As they pass through the eruption cloud the fragments become rounded by abrasion with other volcanic debris. Due to the moisture in the air the grains become encased in ash and dust to form darker outer rims as can be seen below.

I came across this outcrop on my Independent Mapping Project and thought it was pretty cool, hopefully you do too!

Watson

Photo: Watson Further Reading: The formation of super continents - http://science.nasa.gov/science-news/science-at-nasa/2000/ast06oct_1/ http://www.sciencedirect.com/science/article/pii/S0040195113001479 Accretionary Lapilli: http://www.glgarcs.net/topics/aclapilli.html

Delicious Lapilli

When volcanoes erupt, they throw out debris of all sizes. The finest particles are referred to as ash, the largest particles are called bombs or blocks. In-between these are lapilli - pieces of volcanic rock somewhere between 2-64 mm in diameter.

Lapilli can form in several ways. Beads of molten lava can be tossed into the air and cool into solid particles before they hit the ground. Fragments of larger, solidified rock can be shattered during an explosion, producing chunks that are lapilli sized. Molten rock can actually be shattered during an explosion, leading to lapilli sized pieces of tephra. Finally, tinier grains of ash can stick together, either due to their own heat or due to water in eruption clouds. This final type of lapilli, accretionary lapilli, grows into progressively larger particles as the grains run into each other, creating close to spherical shapes.

These lapilli were found on the beach of Fuerteventura in the Canary Islands. The number of distinct spheres seemingly sticking together suggests to me that they are accretionary lapilli. The particle to the left is how they originally look; to the right you see how they appear after being slowly weathered by the ocean. I do not believe they would be edible despite this appearance.

-JBB

Image credit: Roger Haworth https://commons.wikimedia.org/wiki/File:Lapilli_850.jpg