When the workers pour cold water on the hot rock, it usually cracks, and is easier for the workers to manually break apart.
(the workers; pour; cold water; on the hot rock) (it; cracks; T:When the workers pour cold water on the hot rock; T:usually) (the workers; to manually break; apart)
the workers it the workers
pour cracks to manually break
cold water on the hot rock
T:When the workers pour cold water on the hot rock T:usually
apart