When two valley glaciers meet to form a larger glacier, the rock debris along the sides of both glaciers merge to form a medial moraine (see figures 12.11 and 12.17 in your text).
(the rock debris along the sides of both glaciers; merge; to form a medial moraine (see figures 12.11 and 12.17 in your text; T:When two valley glaciers meet to form a larger glacier) (two valley glaciers; meet; to form a larger glacier) Context(two valley glaciers meet,List([5, 29))):(two valley glaciers; meet to form; a larger glacier)
two valley glaciers meet,List([5, 29))
the rock debris along the sides of both glaciers two valley glaciers two valley glaciers
merge meet meet to form
to form a medial moraine (see figures 12.11 and 12.17 in your text T:When two valley glaciers meet to form a larger glacier
to form a larger glacier
a larger glacier