The crack is around 30km (20 miles) wide and 60m (200ft) deep. The crack keeps growing every day.
NASA expect the iceberg to break off early next year and that it will be around 880 sq km. Its about the size of German city Berlin.
The area, called Pine Island Glacier, has been thinning for the last few years so the breakup is not a huge surprise.
The enormous iceberg could be dangerous to shipping but it will be monitored closely, when it finally breaks off.