Two giant slabs of ice are about to hit each other in Antarctica, possibly with spectacular results, say Nasa experts.
The B-15A iceberg (right) heads for the Drygalski Ice Tongue (top left)
A 160km-long iceberg is heading on a collision course with a huge floating glacier in the sea near the US McMurdo Research Station.
The B-15A iceberg should collide with the Drygalski Ice Tongue no later than 15 January 2005, though it is slowing.
US space agency scientists are studying the iceberg's progress by monitoring satellite images of the region.
The Modis instrument on Nasa's Aqua and Terra satellites captured 13 images of the shifting B-15A iceberg between 9 November and 2 January 2005.
"It's a clash of the titans; a radical and uncommon event," says Robert Binshadler, a researcher at Nasa's Goddard Flight Center in Maryland, US.
"Even a tap from a giant can be powerful. It will certainly be a blow far larger than anything else the ice tongue has ever experienced."
When the two ice giants hit each other, the impact will probably "dent their bumpers", according to Dr Binshadler.
The edges could crumple and ice could pile off or drift into the Ross Sea.
The Drygalski Ice Tongue is a rivet of thick ice that grows out over the Ross Sea from a land-based glacier on Antarctica's Scott Coast.
"Ice tongues do break off on occasion," says Binshadler. "It would only take one thin area on the ice tongue to make it break off."
The Nasa researcher added that there was no guarantee Drygalski would break off, but that "this is the toughest blow it has ever had to deal with".
B-15A has already been causing trouble for penguins
The B-15A iceberg is a 3,000 sq km behemoth that has a history of causing trouble. It is the largest fragment of a much larger iceberg that broke off from the Ross Ice Shelf in 2000.
This year, it trapped sea ice in McMurdo Sound. The currents that normally break the ice into pieces and sweep it out into the Ross Sea have not been able to clean out the Sound.
So winter's thick ice remains intact - causing problems for Antarctic residents.
That means penguins have to swim greater distances to reach open waters and food.
As a result, there is a danger many chicks could starve, according to Antarctica New Zealand, the government organisation that oversees the country's research.