Thanks for your research and posting it here!

I found it particularly interesting because of the description of "where the heat comes from". Texas also has hot springs. The town of Marlin, north of Austin on I35 and half way between Austin and Dallas, was a spa town in the 40's with a Hilton Hotel and the baths. It was touted as the "deepest" source of a hot spring on earth. The old hotel is still in use and has a multiuse large room (high school seniors were decorating it for the Senior Prom when I visited a couple of years ago) and small offices. The City Hall maintains a pump with a concrete trough, from which I brought home a jug of very strong sulphur water.

Going east from Dallas toward Arkansas, you can see several hot spring eruptions in cornfields along the highway. South of Austin, along I35 you can see the mound of an inactive volcano, also in a cornfield. These are related to the Balcones Fault.