The question is, what is likely to trigger the correction
Put a frypan with some cooking oil on an electric (so no open flame) stove and turn the heat up to maximum.
In due course the oil will catch alight. Once it gets hot enough you could make it catch fire sooner by holding a lit match or some other flame near it but ultimately a point comes where it's so hot that it ignites of its own accord.
Now to bubbles, the same principle applies. If it reaches a high enough point then it'll fall over eventually simply due to running out of greater fools to buy the asset in question. A trigger, like the flame near the hot cooking oil, will make it happen sooner but it still happens eventually even without an obvious trigger as such.
If there's an trigger then that's really just coincidence. The crash happens anyway, all the trigger does is change the timing a bit.
Given the dominance of automated trading and index ETF's which have no discretion as to what stocks they buy or sell my personal expectation is that whenever the next crash does come, it'll happen real quick once the tipping point is reached.
what will be the effect of the correction on the Australian market?
Hard to know with any certainty but if the US tanks then we're not going up that's for sure.
Bubbles which I think exist at the moment:
US stocks.
Australian residential property.
Bitcoin. It's hard to put a fair value on it but when something's going up more than 10% in a day and it's being reported as mainstream news that's a pretty big warning sign.
Bonds although that one could take a very long time (decades) to play out in full.
In a less specific context I'll add US shale oil to the list. It's a valid industry certainly but one that's dependent on surplus capital looking for somewhere to go. Cut that off, and that will happen someday, and it's a very different picture. The US shale industry isn't going to disappear but it's not going to put the Saudi's or Russians out of business either no matter what the hype says.