Prince William Sound has the greatest concentration of tidewater glaciers in Alaska, including Columbia Glacier, the stunning grandfather of glaciers in the Sound. Covering about 440 square miles, Columbia Glacier is 40 miles long and more than three miles wide at its face, which rises up to 250 feet above the water and plunges an incredible 2,000 feet below.

Although it’s the second largest of its kind in Alaska and still extends 15 miles out into its ancestral fjord, Columbia Glacier is but a minor remnant of the vast glacier that only a few thousand years ago filled Prince William Sound; its face reached a height of 4,000 feet.

Since 1982 the glacier has been in rapid retreat, at a rate averaging a half-mile per year. This retreat has filled Columbia Bay with icebergs, and tour boats can no longer get within six miles of the face. Ice in the bay has also caused navigational hazards in Prince William Sound, and it was to avoid ice that the Exxon Valdez took its fateful shortcut near, and onto, Bligh Reef.

Scientists speculate that by the time the glacier stops its current rate of backward movement, a new fjord 25 miles long will be exposed, into which several calving glaciers will flow.