The grandma Lake Toya and its generations, Hokkaido

The earth at its younger age was very active with crust movement.  The volcanic eruptions could be much bigger than what we can see in the past centuries.  Lake Toya was one of the examples.  A big volcanic eruption with the crater left as a lake.  Later on, smaller scale of volcanic eruption took place around the ring of Lake Toya.  Usu volcanic mountain (有珠火山) was one and followed by a smaller neighbour Showashinzan (昭和新山).  Perhaps we can name Lake Toya as the grand mother, Usu as the daughter and Showashinzan as the grand daughter.  There may be more grand kids coming along.