The extent of the ice on the Polar Ocean is dependent on the low salinity of the Arctic waters - a saltier sea would not freeze over to such a degree. The Polar Ocean is separated from the Atlantic Ocean by a barrier of islands that inhibits their inter-circulation. This island chain is formed from what was once a single island known as Iceland. It consisted of lavas that erupted from the Mid-Atlantic Ridge as the crustal plates of Europe and North America (the Eurasian Plate and the North American Plate) moved away from one another. As this movement continued, enlarging the Atlantic Ocean, Iceland, straddling the mid-oceanic ridge, split into two parts, each moving in opposite directions. The continuing volcanic activity spawned a string of new islands in the growing gap between the two p