I observed this radial structure in weathered basic volcanic rocks located in an arid region. The scale of the image spans approximately 20 meters. I am curious about the origin of this radial structure. Could it be solely a result of weathering processes, or might it also be associated with the original volcanic eruption?
The geologic structure visible in the image appears to be a radial columnar jointing feature, which is commonly associated with cooling fractures in volcanic rocks. Given the weathered nature of the rock and its basic volcanic composition, this structure likely formed due to contractive cooling of lava.
Possible Origins of the Structure:
Conclusions:
- The radial pattern is likely a result of primary volcanic cooling rather than being purely a weathering feature.
- Given the location in an arid region, erosion has played a role in exposing this cross-section.
- Further field observations (rock texture, mineralogy, and stratigraphic context) would be needed to confirm whether this is a volcanic dome remnant, a sill, or a plug.
It could be a mega-pillow. There are several cases like this (but not so weathered).
Michele
Thank you so much, very interesting
It would be great, if you could kindly lead me to some examples (pictures or publications).
Yes Nima,
you can check here:
https://iugs-geoheritage.org/geoheritage_sites/muriwai-megapillow-lava-flows/
https://idese.cultura.gov.it/place/megapillow-di-gutturu-forru/
Cheers,
michele
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