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

its a map of something

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain