premise: the grand canyon is a kind of canyon sent2: a river is a kind of flowing body of water sent3: the colorado river is a kind of river next to the grand canyon sent4: if something requires something else then that something else is important to that something sent5: the colorado river is a kind of river sent6: if something is formed by something else, then that something else is required by that something sent7: most canyons are formed by flowing rivers through erosion over long periods of time.
hypothesis: roots take in iron from the soil