A cartographic mystery is at the heart of our Geo Quiz. We're looking for the name of the sea that lies between Australia and New Caledonia. This sea has been in the news recently because when you call up the area on Google Maps, there's a curious black blob in the middle of the water. And that blob is identified as Sandy Island on some other maps. An Australian scientist recently sailed to the spot to see if she could solve the mystery, "We were wondering what this big, black blob was doing there so that's why we asked the captain to change the course just a little bit so we could travel through the island, this supposed island." Can you name the sea off the coast of Queensland that's home to a phantom island? Historically speaking, maps are works-in-progress. They have to be constantly updated and revised to reflect changing borders or new place names. But in this era of satellite photos, and Google Earth, it's very rare to find actual cartographic errors. Australian scientist Maria Seton found one, though, while on a research vessel in the Coral Sea, the answer to our Geo Quiz. Seton and other researchers were studying plate tectonics underneath that body of water. When they looked at a Google Map of the Coral Sea, they noticed a big black blob. That blob appears on some maps as Sandy Island. Seton says they decided to move in closer to investigate. "We were actually out in the eastern Coral Sea conducting a scientific research expedition and when we were approaching the area of this supposed island we saw that our scientific maps showed there was an island there and yet the navigation charts on board the vessel showed that we had a water depth of 1400 meters. So that's when we started getting suspicious." That's approximately 4600 feet, or less than a mile. But that's still deep seawater. Seton double-checked her GPS location and sure enough, right where her maps showed an island there was no island – just the deep Coral Sea. So what happenned to Sandy Island? One theory is there used to be a volcanic island there that somehow became submerged. But Seton isn't buying that. "It definitely hasn't disappeared. We believe that there was just never an island there. All the navigation charts on board and all the ships that have gone through the area in the past and taken depth readings haven't found that there's an island there. It must have just been an error that has been propagated through these world maps. I mean we've got water depths of 1400 meters so it's not really something that is within the human time scale that things would have shifted or changed… It's still a bit of a mystery how this error was propagated. " For now, if you see a black blob on your world map at 19 ° 13"² 12"³ S, 159 ° 55"² 48"³ E, you might just color it in bluish green, like the rest of the Coral Sea.