I live out in the sticks. The closest recognizable town is about twenty minutes drive, not really far enough away, but it will do. Should I take it into my mind to walk out my front door, something that happens on a regular basis, and to turn my feet south, I can walk for several miles through woods and fields, down country roads and across railroad tracks, and I will see no indication whatsoever that I have passed from The Great State Of Tennessee into the equally Great State Of Mississippi. The land remains essentially unchanged, the population mix is the same as I walk, the fields and houses continue to be the fields and houses of rural mid-southeast North America. Should I take it into my head to get into my automobile and drive a considerable distance south, say about seven hundred miles or so, I will notice the land is marginally different.
Palm trees dot the countryside and the average temperature is somewhat warmer.
At no point, however, do I come to a spot at which the countryside abruptly changes from mid-south warm and muggy to farther south warmer with clusters of palm trees. In the event I should decide to travel west some fifteen hundred miles, I could find myself driving through land that varies considerably from the forest and farm land I call home. This land to the west is hot and dry and rocky. However different my home is from this hot and dry land, at no place do I come to a dividing marker at which there is a sudden change from humid forest and farm to dry and rocky. The changes become evident very gradually as I drive.