What is Calving? In Glacier Bay

Crash! Tidewater glaciers offer a tremendous display of power.

NPS Photo

If a glacier is fed by enough snow to flow out of the mountains and down to the sea, it is called a "tidewater" glacier - the type many people come to Glacier Bay to see. The interface of glaciers and ocean water is dynamic and complex. Compared to glacial ice, seawater is warm and highly erosive. As waves and tides undermines some ice fronts, great blocks of ice up to 200 feet may break off or "calve" and crash into the sea. The explosive sound, towering splash, and subsequent waves can be spectacular.

Icebergs may last a week or more. They provide perches for bald eagles, cormorants, and gulls, as well as haul-outs for harbor seals and sea otters. When passing close by, passengers can hear splashes and crackles as melting water drips and the ice deteriorates. The ice pops and sizzles as it releases ancient air first trapped between the delicate snowflakes and then frozen in under pressure – a phenomenon called “bergie seltzer.” Colors betray a berg's nature or origin. White bergs hold many trapped air bubbles. Blue bergs are dense and are likely recently calved. Greenish-blackish bergs may have calved off glacier bottoms. Dark-striped brown bergs carry morainal rubble – rocks that the glacier acquired on its journey down the mountain.

Want to HEAR a glacier in action? Click here to visit our glacier soundscapes webpage.