Mount Manaro, on the island of Ambae, reportedly began spewing out ash and steam on 27 November and is said to be continually shaking.
There are fears that if Manaro did erupt it may also unleash a mud stream from a lake inside its crater.
Vanuatu - a chain of 83 islands - lies just over 2,000km north east of Sydney.
A huge ash blanket from a major eruption might raise the altitude of the islands. Huge volcanic eruptions, though hell on human populations nearby, fine volcanic dust creating a sort of concrete in human lungs, have a long history of lowering global temperatures. The best example is the eruption of Mt. Tambora which I blogged months ago. Mt. Tambora, the largest eruption in modern human history, caused "The Year Without a Summer" and the "Year of Famine" in Europe, but it was much cooler for quite a while. Though large volcanic eruptions spew huge volumes of CO2 into the atmosphere, far beyond what man can accomplish, the ash cloud often leads to global cooling.