If the glacier is confined to a valley, it will often carry rocks that have tumbled down from the mountain's slopes to rest on the glacier's surface.
(the glacier; is confined; to a valley) (it; will carry; rocks that have tumbled down from the mountain's slopes; T:often) (rocks; have tumbled; down; from the mountain's slopes) (rocks that have tumbled down from the mountain's slopes; to rest; L:on the glacier's surface)
the glacier it rocks rocks that have tumbled down from the mountain's slopes
is confined will carry have tumbled to rest
to a valley
rocks that have tumbled down from the mountain's slopes T:often
down from the mountain's slopes
L:on the glacier's surface