Their related because of how they are formed both have a relationship with volcanoes hope it helps :)
The metaphor in this statement is "the great millstone" it kind of qualification word it express how big the time was.
But in reality, millstone doesn't even have a relationship with the time.
So "the great millstone" is a metaphor.
Answer:
can you please like translate it to English?
Force majeure I believe so.
