Kay Ryan is often praised for her "big little poems." The poems are little because, like "Turtle," they typically don't have many lines. Plus, the lines themselves are often short. Even many of the words are short and familiar, reinforcing the impression of something small and simple and accessible. But Ryan's poems are also "big" in the sense that they are packed with ideas, including deep and wide-ranging thoughts about the meaning of life, as well as densely interwoven sounds and images that further enrich our experience of the poems.
Actually, Kay Ryan said it best. (She usually does, as a matter of fact; reading her commentary about poetry is almost as fun as reading the poems themselves!) For her, a poem is "an empty suitcase that you can never quit emptying." In fact, "It's a clown suitcase: the clown flips open the suitcase and pulls out a ton of stuff." For those of us who are scared of clowns, it might be better to picture Mary Poppins pulling full-sized furniture out of her small but bottomless carpet bag, but you get the idea.