Question: Triple-A Plowed Under focused on a period of severe dust storms that was known as what?
Sentence (from "Dust Bowl"): With insufficient understanding of the ecology of the plains, farmers had conducted extensive deep plowing of the virgin topsoil of the Great Plains during the previous decade; this had displaced the native, deep-rooted grasses that normally trapped soil and moisture even during periods of drought and high winds.
Relevant evidence: No