“It takes a few years but once it’s cemented, it’s fairly resistant to ocean currents and to rain and other types of weather-related erosion phenomena,” he added.The first island, Sholan Island, emerged at the end of 2011. “According to news reports,” NASA noted, “fishermen witnessed lava fountains reaching up to 90 feet tall.” That was December 18; by December 23, satellite images show the new land form. For a total of 25 days, the eruption continued and the island grew, according to the Nature Communications paper.Jadid Island, the second new one, came in 2013 after an eruption that began on September 28. It lasted 54 days, but the island showed up on satellite images after less than a month. Though larger than the first island, Jadid still expanded to a little more than half a mile in diameter.Jonsson said he and colleagues haven’t been able to visit the new islands because Yemen owns them, making for a tricky political situation. But Yemeni scientists have been to at least Sholan Island, and Yemeni fishermen go to the remote archipelago from time to time. He does know that islands formed in shallow water less than 330 feet deep, circumstance he suspects would foster much marine activity (though as a geophysicist who studies earthquakes, he made clear that’s not his expertise). For now, it seems, these scientists simply feel lucky to have experienced such a unique phenomenon. “They are quite rare,” Jonsson said. “If they only happen every hundred or 200 years, odds are you haven’t seen one.” To read the Nature Communications paper, click here.MORE FROM WEATHER.COM: A Unique Perspective on Common Places

Ice breaks off into the sea at the Thwaites Glacier, one of the most vulnerable and fastest moving glaciers of the West Antarctic Ice Sheet. (Daily Overview/Digital Globe)