THE GLACIERS OF ALASKA
It was on June 11 and 14, 2008 that Nena and I finally saw during our cruise on board the Island Princess the
Alaskan Glaciers at Glacier Bay and the Mendenhall Glacier in Juneau. Glacier Bay is quite popular with cruise
ship passengers because of the huge glaciers descending hundreds of feet to the water. Seeing these magnificent
glaciers was one of the main highlights of our trip to Alaska and I must say that it was all worth it and proved
to be very educational on my part as well.
Prior to our trip, I didn't know anything much about glaciers and how they really looked like. Almost all the
mountains in Alaska are covered with snow and at first I did not know how to recognize the presence of glaciers.
I finally learned that a glacier is a large, slow-moving "river of ice," formed from compacted layers of snow,
that slowly deforms and flows in response to gravity. Over many years, the fallen snow compresses into large,
thickened ice masses and when snow remains in one location long enough to transform into ice, a glacier is formed.
Glaciers are unique due to their ability to move and because of their sheer mass, glaciers flow like very slow
rivers. Ice flow down mountain valleys, fan across plains, or in some locations, spread out to the sea. Movement
along the underside of a glacier is slower than movement at the top due to the friction created as it slides along
the ground's surface. The upper layers of glaciers are more brittle, and often form deep cracks known as crevasses
as they move. The
distance between the two separated parts while touching and rubbing deep down, frequently widens
significantly towards the surface layers, many times creating a wide chasm.
These crevasses make travel over glaciers hazardous. Subsequent heavy snow may form a fragile snow bridge,
increasing the danger by hiding their presence at the surface.
I also found out that glaciers have a distinctive "blue tint" that makes it appear quite different from ordinary
white snow. The blue color is actually created for the same reason that water is blue, that is, its slight
absorption of red light due to an overtone of the infrared OH stretching mode of the water molecule.
Glacial ice often appears blue when it has become very dense. Years of
compression gradually make the ice denser over time, forcing out the
tiny air pockets between crystals. When glacier ice becomes extremely
dense, the ice absorbs all other colors in the spectrum and reflects
primarily blue, which is what we see. You will surely notice the blue tint of glaciers when viewing the attached
photographs I took of the glaciers in Alaska.
And there are, after all, two main types of glaciers: Alpine Glaciers and Continental Glaciers ... alpine glaciers
are those that are found in mountain terrains, and continental glaciers are those which cover very larger areas.
The largest glaciers are actually continental ice sheets. These are enormous masses of ice that are not visibly
affected by the landscape and that cover the entire surface beneath them, except possibly on the margins where
they are thinnest. Antarctica and Greenland are the only places where continental ice sheets currently exist.
These regions contain vast quantities of fresh water.
The volume of ice is so large that if the Greenland ice sheet melted, scientists predict that it would cause sea
levels to rise some six meters (20 ft) all around the world. And if the Antarctic ice sheet melted, sea levels
would rise up to 65 meters (210 ft). Should this happen, there is no doubt that most of the Hawaiian islands
and numerous other places will all disappear from the face of the earth.
The glaciers that are found in Alaska are refered to as "Tidewater Glaciers", or glaciers that flow into the sea.
As the ice reaches the sea pieces break off, or "calve", forming icebergs. Most tidewater glaciers calve above
sea level, which often results in a tremendous splash as the iceberg strikes the water. If the water is deep,
glaciers can calve underwater, causing the iceberg to suddenly explode up out of the water. As we were viewing
the different glaciers at Glacier Bay, from our ship we saw for ourselves the actual "calving" of some glaciers
and we also saw the large splashes it made on the water.
The Mendenhall Glacier is a glacier about 12 miles (19 km) long and has a 1.5-mile face which is located in
Mendenhall Valley, about 12 miles (19 km) from downtown Juneau (The capital city of Alaska) in the southeast
area of the U.S. state of Alaska. It is one of many "rivers of ice" in southeast Alaska formed during the Little
Ice Age which began about 3,000 years ago.
On a sunny day the Mendenhall glacier is beautiful with blue skies and snow-capped mountains in the background.
On a cloudy day it can be as impressive as the ice turns shades of deep blue. You can visit on your own or take
an organized tour. There is an interesting visitor center near the glacier and several hiking trails in the area.
Fed from an icefield high above Juneau, the Mendenhall glacier is a dynamic flowing force, grinding and scouring
everything in its path as it carves its way down to the sea. The ice flows forward at an average rate of 2 feet
per day, but at the very same time, it wastes away at a slightly faster rate. Wastage occurs through melting or
by large pieces of ice breaking off the face of the glacier which is known as "calving" and produces the icebergs
floating in Mendenhall Lake.
We were told by an Alaskan Park Ranger that most of the world's glaciers are found near the north and south poles,
but glaciers also exist on all of the world's continents, even Africa. Extensive glaciers are found in Antarctica,
Patagonia, Canada, Greenland and Iceland. Mountain glaciers are widespread e.g. in the Andes, the Himalaya, the
Rocky Mountains, the Caucasus, the Alps, in Norway, Japan, Turkey and the Iran. The large islands of Papua New
Guinea and New Zealand also have glaciers.
On mainland Australia no glaciers exist today, although a small glacier on Mount Kosciuszko was present in the
last glacial period, and Tasmania was widely glaciated. On New Zealand's South Island the West Coast bears the
Fox and Franz Josef Glaciers. In New Guinea small glaciers are located on its highest summit massif of Puncak
Jaya. Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya and in the Ruwenzori Range.
The following are some facts about glaciers:
- Presently, 10% of land area is covered with glaciers.
- Glaciers store about 75% of the world's freshwater.
- Glacierized areas cover over 15,000,000 square kilometers.
- Antarctic ice is over 4,200 meters thick in some areas.
- In the United States, glaciers cover over 75,000 square kilometers,
with most of the glaciers located in Alaska.
- If all land ice melted, sea level would rise approximately 70 meters
- Glacier ice crystals can grow to be as large as baseballs.
- The land underneath parts of the West Antarctic Ice Sheet may be up to
2.5 kilometers below sea level, due to the weight of the ice.
- North America's longest glacier is the Bering Glacier in Alaska,
measuring 204 kilometers long.
- The Kutiah Glacier in Pakistan holds the record for the fastest glacial
surge. In 1953, it raced more than 12 kilometers in three months,
averaging about 112 meters per day.
- In Washington state alone, glaciers provide 470 billion gallons of
water each summer.
- Antarctic ice shelves may calve icebergs that are over 80 kilometers
long. Almost 90% of an iceberg is below water and only about 10% shows
- The Antarctic ice sheet has been in existence for at least 40 million
Today, glaciers often are tourist attractions in mountainous areas. But glaciers are also a natural resource,
and people all over the world are trying to harness the power of these frozen streams. People living in the
city of La Paz, Bolivia, rely on glacial melting from a nearby ice cap to provide water during the significant
dry spells they experience. Although parts of Japan receive tremendous amounts of snow, there are no glaciers.
Because the Japanese must endure frequent droughts, scientists are examining ways to create artificial glaciers
that could provide more water for people when the weather is dry.
In Switzerland' s Rhone Valley, farmers have irrigated their crops for hundreds of years, by channeling meltwater
from glaciers to their fields.
Scientists and engineers in Norway, Canada, New Zealand and the Alps have worked together to tap into glacial
resources, using electricity that has been generated in part by damming glacial meltwater.
The attached photographs were those that I took of the different glaciers we saw in Glacier Bay as well as the
Mendenhall Glacier in Juneau. Just click on the link shown below for the slideshow:
The Glaciers of Alaska
It is hoped that you have learned something about glaciers and that you will also enjoy
viewing the photographs.