(10) Vast coal beds accumulate one on top of another, each as original swamp deposits on order of 100 feet thick, all in one year.
(10) Vast coal beds; accumulate; one on top of another, each as original swamp deposits on order of 100 feet thick, all in one year)
10) Vast coal beds
accumulate
one on top of another, each as original swamp deposits on order of 100 feet thick, all in one year