I was recently looking at some aerial imagery of a Midwest farm and wondering how to interpret a couple things. First, in the 1938 imagery, there are several fields that appear to have weird geometrical lines in them... Could these be related to the installation of crude tile drainage systems? Just tillage? They seem too frequent to be haybails, as the field is on the order of hundreds of feet wide.
Also, in a ravine draining into the river, there appears to be a relatively abrupt elevation change as if there is a structure or human-made mound of some kind within it, but I am not sure how to interpret this? Any idea what these features could be?
Pictures of the 1938 photograph as well as modern Google Earth snapshots also attached.