Ridges of sea ice packing car-sized chunks of the cold stuff slammed onto a road in this northern Alaskan town in quantities not seen in nearly three decades.

Two ice surges, known to Alaska Natives as ivus, stunned residents who had never seen such large blocks of ice rammed ashore.

"It just looked like a big old mountain of ice," said L.A. Leavitt, 19, who left his nightshift job at the city to check out the ridges.

Ivus are like frozen tsunamis and crash ashore violently. They have killed hunters and are among the Arctic's most feared natural phenomena.

The ivus crashed ashore Tuesday after strong winds from Russia and eastward currents began pushing pack ice toward Barrow last weekend, said North Slope Borough disaster coordinator Rob Elkins.

By late Monday, thick, old sea ice known as multiyear ice had shoved younger, thinner ice onto shore.

Witnesses here said the northernmost ridge was about 20 feet high and 100 feet long and contained car-size blocks. Ice left a coastal road with only one lane, they said.

"It was just an amazing sight," said Elkins. "It looks like huge stacks of huge ice cubes."