A tsunami's icy reach

The March 2011 earthquake and subsequent tsunami off the coast of Japan did unimaginable damage. The tsunami was several meters high, marching a long way inland, and wiped out entire towns. It also swept out to sea, expanding across the planet. By the time it hit the Antarctic ice shelf -- 13,000 km away, taking less than a day -- it was well under a meter high. But water is dense (a cubic meter weighs a ton!) and that much of it hitting the ice can cause it to flex and break. And that's precisely what happened: