What does Professor Worster identify as the primary cause of the Dust Bowl?

Explanation:

ating and exploiting the land for all it was worthcame about because the expansionary energy of the U.S. had Finally encountered a voluble, marginal land, destroying the delicate ecological balance that had evolved thereHurt ExcerptDust storms in the southern Great Plains, and indeed, in the Plains as a whole, were not unique to the 1930sMany factors contributed to the creation of the Dust Bowl – soils subject to wind erosion, drought which killed the soil-holding vegetation, the incessant wind, and technological improvements which facilitated the rapid breaking of the native sod

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