A massive 1,200 square mile iceberg threatens to block thebreakup of ice in the Ross Sea and prevent resupply of theUS’s sprawling McMurdo base in Antarctica.

The iceberg broke off the Ross ice shelf in 2000 and hasbeen drifting since then. It is the largest iceberg everrecorded. On Wednesday, it ran aground against Ross Islandand is in danger of becoming wedged against a smallerisland, which would result in the isolation of the McMurdobase from resupply by sea during the brief Antarctic summer(late November–early February).

The berg contains enough fresh water to supply theMississippi River for a century, or to cover New Zealand toa depth of eighteen feet. It will take decades for it tomelt, though, and it will not raise sea levels because it ismade up of sea ice, not ice that started out on land andslid into the sea.

There are over a thousand personnel at McMurdo, and it hasan ambitious scientific program.

The berg is also affecting Mt. Erebus, Ross Island’s activevolcano. As it presses against the island, it has cut offthe path of eruptive material in the volcano, preventing itfrom reaching the surface. Strange sounds and tremors arebeing felt hundreds of miles into the Pacific as a result.The long term effect on the volcano is unknown.

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