What is the best evidence that the igneous rock layer called the Purcell Sill intruded underground between layers of sediment, rather than flowing out on the surface as a lava
flow that was then buried beneath later sediments?

tropical storm katrina, and it made landfall between miami and fort lauder-dale, florida, as a category 1 hurricane (a storm that, on the saffir-simpson scale, exhibits winds in the range of 74–95 miles per hour [119–154 km per hour]). sustained winds of 70 miles per hour (115 km per hour) lashed the florida peninsula, and rainfall totals of 5 inches (13 cm) were reported in some areas. the storm spent less than eight hours over land. it quickly intensified when it reached the warm waters of the gulf of mexico.

this should answer you're question