An iceberg that has broken off from an ice shelf. Newly formed tabular icebergs have nearly vertical sides and flat tops. In the Antarctic, they may be tens of kilometers wide, up to 160 km (100 miles) long, and as much as 300 m (1000 ft) thick, with about 30 m (100 ft) exposed above the sea surface. In the Arctic, large icebergs of this type are called ice islands, but they are considerably smaller than the largest of the antarctic variety.