There are a number of stories on the net regarding the new continent of Zealandia. The Wikipedia article includes a video giving one person’s idea of how he sees history going where Zealandia is concerned. I have to disagree with him
At the north of Zealandia are what we now call the islands of New Caledonia, a French possession now in a state of quasi independence. The first inhabitants of New Caledonia were the Lapita who apparently colonized the islands back around 1600 BC, having migrated east from New Guinea. Given a continent of 1.9 million square miles instead of a few islands of some 7,172 square miles I would expect the Lapita to have explored and settled the lands south of their initial coastal settlements. But I’m not really ready to tell that tale. Instead, I’d like to point out one big thing.
Eastern Australia is a warm land thanks to a current coming down from the Equator. With the tropical waters you get the Great Barrier Reef. With Zealandia located where it is were it above water the current in question would be diverted so it flows east of Zealandia. With the current blocked you would get a cold water current coming up from Antarctica, meaning a cold sea off the east Australian coast. This Zealandia Barrier Reef would most likely extend south until the current supporting it reached a peninsula extending east. This land — which I’ll call the Chatham Peninsula after the Chatham rise of the real world — would separate the Zealandia current north of Chatham Land from the Antarctic current south of it. The mixing of the warm and cold waters east of the peninsula would most likely mean a lot of tumultuous weather at what I’ll call Chatham Cape.
But that’s another matter. Where the east coast of Australia is concerned in the Zealandia Earth things would be a lot different than they are here.
You see, the Great Barrier Reef acts as a shield of sorts from the waves coming from the south and east. In effect their effect is to smooth out the waves and eat up their energy. Without the reefs the waves would just keep on keeping on with no moderation to crash against the coast at basically full force. To give you an example of what I’ll be talking about here I’d like you to consider the California beach town of Encinitas.
Encinitas is a coastal city in the northern part of San Diego County, and being situated on the coast as it is it has seen a fair share of coastal erosion. Erosion to such extent that as with other Northern San Diego County cities a fair amount of land has been lost to the sea; a few city blocks at least.
Now consider the Zealandia Australia’s eastern coast. A coast unprotected from the waves coming from the south and east. A coast subjected to millions of years of constant erosion. In this world Australia’s Eastern Highlands constitute a coastal range overlooking the Eastern Sea. a range which is constantly being worn away by the great waves of the sea. In this sense you could say that the eastern Australian coast is like the rockbound shores of Maine in North America. There’s more that could be added, but at the moment I’ve run out of steam.
You’re welcome to continue speculating on how this part of the world would be different . I may write more, but first I need to get a good night’s sleep.