The recent Google Earth imagery update includes an image of a new island formed from Hunga Tonga and Hunga Ha’apai, part of the Tonga archipelago in the South Pacific Ocean. Hunga Tonga and Hunga Ha’apai used to be two islands with a submarine volcano between them. Then, in December 2014, the volcano started erupting and by mid-January 2015 a new island had formed with the volcano’s crater in the centre. See Wikipedia for more details.
Hunga Tonga and Hunga Ha’apai in 2014, before the 2014/2015 eruption
The new island, May 2016
See ground level photos here.
Another example of islands that have joined together through volcanic eruption that can be seen in Google Earth imagery is Nishinoshima, Japan.
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Find the locations above in Google Earth with this KML file.