August, 2016

Before going to Glacier Bay, we took a train ride on the White Pass & Yukon Railway, from Skagway to the Canadian border. The route took us between mountains where we saw several glaciers.

When explored by Captain George Vancouver in 1794, Glacier Bay was filled with a single great glacier that was more than 4,000 feet thick, up to 20 miles wide, and that extended more than 100 miles. When John Muir explored eighty-five years later, the ice had retreated almost 50 miles up the bay.

Glacier Bay National Park is comprised of over 3 million acres of stunning beauty, in which glaciers play a major role. The park is part of a binational UNESCO World Heritage Site and a Biosphere Reserve. There are eleven glaciers that reach the sea in Glacier Bay. These are tidewater glaciers, defined as valley glaciers that flow far enough to reach the sea. There are only three places in the world where you can see tidewater glaciers: Alaska, Chile and Scandinavia.

Tidewater glaciers calve many small icebergs. Though not as large as Antarctica’s icebergs, they can still cause trouble. We learned from park rangers who came onboard our ship, about different types of icebergs. White bergs hold trapped air bubbles; blue bergs are very dense and hold little air (they absorb white light while reflecting blue); and greenish-black bergs have calved off from the bottom of the glacier, carrying moraine, the rocky rubble picked up along their journey to the sea.

Icebergs come in many shapes as well. There are two basic shapes: tabular and non-tabular. Tabular icebergs have steep sides and a flat top, with a length that is at least five times the height (like a large sheet). Non-tabular icebergs have several different shapes: wedge (steep edge on one side and a slope on the other side), dome (rounded top), drydock (with a channel caused by erosion),  pinnacled (with one or more spires), and blocky (similar to a tabular, but the length is less than five times the height).  We didn’t see any large icebergs today.

We passed by Margerie Glacier, which is about 21 miles long, and growing at a rate of about 30 feet per year. This tidewater glacier was named for a French geologist and geographer, Emmanuel de Margerie.

 

 

Grand Pacific Glacier is a 25 mile long glacier that is located partly in British Columbia, Canada. This glacier is full of moraine and rocks from landslides that extend across almost two-thirds of the ice face. In some areas, this debris is more than 3 feet deep. The moraine helps insulate the ice, slowing the melting.

The approach to Johns Hopkins Glacier is quite dramatic. We caught glimpses of it behind a mountain before we reached the inlet where it’s located. This twelve mile long glacier is one of the few in the park that is advancing.