When the tree fell into the lake, large rocks were still trapped in the roots, causing that end of the log to sink down into the water.
(the tree; fell; into the lake) (large rocks; were trapped; in the roots; causing that end of the log; T:When the tree fell into the lake; T:still) (large rocks; causing; that end of the log)
the tree large rocks large rocks
fell were trapped causing
into the lake
in the roots causing that end of the log T:When the tree fell into the lake T:still
that end of the log