A furriner writes:
'Dusk' or 'twilight' sound like an event - which they are, to people who live in lower lattitudes (eg, the US lower 49).
'Gloaming' is more like a condition that goes on for a long time - as indeed dusk does in Scotland where this word is most popular. For much of the year, there is a two hour period where the daylight gradually fades into night and gloaming describes that transitional time.
Andrew