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13 January 2015 Last updated at 17:36 GMT
Tonga is a small island in the Pacific Ocean, east of Australia.
Experts from New Zealand's GNS Science agency said volcanic activity had been recorded for a few weeks.
It's thought the volcano may have started under the ocean but erupted out of the water, creating a tiny new island.
Airlines hope they can carry on sending planes to Tonga on Wednesday, as long as the ash has cleared.
Flights to the island of Tonga have been cancelled after a volcano erupted, spewing ash into the sky.