The sand on the dune next to the hole began to tumble and within seconds Mark was buried under the pile of sand and a mound formed over the boy.
(The sand on the dune next to the hole; began; ) (The sand on the dune next to the hole; to tumble; ) (seconds; was buried; L:under the pile of sand and a mound) (a mound; formed; T:over the boy)
The sand on the dune next to the hole The sand on the dune next to the hole seconds a mound
began to tumble was buried formed
L:under the pile of sand and a mound
T:over the boy