If I did this correctly, I have attached a screen shot showing a white band across the taxiway in front of the aircraft. As far as I know, the only scenery is the default scenery included with FSX-SE. The white appears to be a canyon because when the airplane crosses it, the airplane falls in.
I have the weather program Active Sky 2016 installed.
When I have MegaScenery Texas South East installed, the only difference is the white band is in a different location and much wider. One other thing, when I restart FSX in a location on the taxiway right in front of a "canyon", the displayed scenery momentarily looks proper, but then the "canyon" appears.
Thanks for your continued assistance.