Satellites operated by the American space agency NASA last month spotted a massive rift in the Larsen C ice shelf in Antarctica.  Scientists are concerned the crack will eventually cause a huge part of the ice shelf to break off.

"The crack completely cuts through the ice shelf but it does not go all the way across it - once it does, it will produce an iceberg roughly the size of the state of Delaware," NASA said in a news release.  That's about 5,000 square kilometers.

The crack in Larsen C is described as 112 kilometers long, more than 90 meters wide, and more than half a kilometer in depth.  If it does break off, the resulting icebergs wouldn't immediately change world sea levels - but it would be enough to add new waters to the ocean before an alarming sea level increase is noted.

Meanwhile, another key glacier in the West Antarctic has been breaking from the inside out, suggesting that the warming ocean is weakening the coastal ice shelf from underneath.  "This kind of rifting behavior provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see a significant collapse in our lifetime," said Ian Howat, associate professor of earth science at Ohio State University. 

Scientists believe that sea levels will rise anywhere from 0.8 to seven meters over the next hundred years - but the sea will rise.