Basalt

 https://youtu.be/IfzSLNEVa9o?si=jwCaaubHsAkdYPtg

Watched the Shawn Willsey video on basal, last night. This morning, went through

the etymology route to help myself remember...

Google AI mode:

                                                                            

                                                                                   

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source: Wikipedia

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The region is home to a chain of volcanoes known collectively as the "chaîne des Puys". The volcanoes began forming about 70,000 years ago, and most have eroded, leaving plugs of hardened magma that form rounded hilltops known as puys. The last confirmed eruption occurred around 4040 BCE.

source:Wikipedia