deepening

nouns

a process of becoming deeper and more profound
deepening
is derived from
deepen
is a type of (narrower)
a process in which something passes by degrees to a different stage (especially a more advanced or mature stage)
"the development of his ideas took many years"; "the evolution of Greek civilization"; "the slow development of her skill as a writer"
development, evolution

adjectives

accumulating and becoming more intense
"the deepening gloom"; "felt a deepening love"; "the thickening dusk"
deepening, thickening