GeoFeature | AA Lava in La Palma island

Reposted from the A-Team PandaCubs by Ralph Tenido



La Palma volcanic island which is part of the Canary Islands have been all around the news since it became volcanically active since the 19th of September 2021.

Videos and photos of the Cumbre Vieja volcano erupting basaltic lava flows have been circulating showing as how it engulfed houses, buildings and anything on it's path.

In this #GeoFeature, we will be highlighting one of the basaltic lava flows observed during the La Palma eruption, which is the basaltic AA lava flow. In the photo at the center, a geologist is taking a sample from the aa lava flow in La Palma, taken on October 31, 2021.

Aa lava is more viscous relative to it's counterpart, the pahoehoe lava. Due to this, it tends to produce a thicker and slower flow with blocky, rough, and angular exterior.

Autobrecciation is the process where the aa lava continuously breaks itself apart as it flows producing blocks called clinkers or scoria.

Clinkers were derived from the distinct clinking noise as blocks are banging with each other as aa lava moves.

Basaltic aa lava and basaltic pahoehoe can be generated from the same volcanic source. However, pahoehoe is only restricted to basaltic lava flows, while aa lava due to its viscosity can range from basaltic to andesitic in compostion. Viscosity, amount of dissolved gases, temperatures, and topography dictates the transitional phase between these two lava flows.


References


[1] Hefferan, K. & O'Brien, J. (2010). Earth Materials. Wiley-Blackwell.

[2] Best, M. G. (2003). Igneous and Metamorphic Petrology. Blackwell

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