They followed the lines of ancient glaciers. They were defined by large farms and grasslands. They followed the system of rivers, canals, and dams. They were naturally defined by deserts, mountains, and seas.
<span>t was the rise of large "factories" that caused an increase in pollution during the industrial revolution, since many of these factories relied on coal for power, which produced lots of exhaust. I don't know if this is one of you're answers.
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