Walker Percy in Lanterns of the Levee wrote about these bubbles. The book is now sort of discounted as racist but it is an excellent book. He lived I do believe on one of those Delta plantations upriver and his descriptions of the levee and how they watched it was fascinating.
Lanterns on the Levee.
Thanks for the tip re: Percy. I'll try to check that one out. (I have a two-foot high stack of books beside my bed now I'm trying to get around to reading - I can handle a few more inches!) /grin
Stay safe and well - things will get better!