I want to know the New Zealand and Australian dialects in English. Please tell me what you know.
I am not a linguist but, I believe it has to do with one of two things. Either changes over time in England and where (in time) the group branched off the main trunk. (this applies to the much-parodied Pirate Accent) Or another common cause of specific dialect in a colony is the regional dialect within the population of England which spawned the group that populated the offshoot colony, thus starting a local dialect in the colony. (Puritans in america) Of course once a colony has begun with a certain accent, it may continue to digress from the original sounds over the years, as people like to do.