ABOUT MATANUSKA GLACIER
The Matanuska Glacier is located in a zone of the continent that has a perfect blend of circumstances for the creation and support of glaciers, many glaciers in fact.
Alaska contains more than 100,000 glaciers of various sizes and importance in the ecosystem. Only 616 are officially named. Matanuska Glacier in our backyard, the foundation for your glacier tour, is one such glacier.
It is a prominent, bold, contrasting and magnificent feature of the landscape that has been appreciated for thousands of years by the region’s original inhabitants and the locals and tourists of present-day Alaska.
The influential conditions here that created and continue to support Matanuska Glacier are the following:
- Proximity to a Large Moisture Source: Matanuska Glacier is located near the Pacific Ocean (Gulf of Alaska), and moist ocean air makes its way inland where, under the right circumstances, it will freeze and fall as snow.
- Elevation: Due to rising bedrock of the Talkeetna and Chugach mountain ranges (both can be seen while taking your glacier tour), moist air from the ocean is forced into higher, colder air. The moisture subsequently freezes and falls as snow, accumulating layer upon layer where, beyond 7000 feet of elevation, there are few risks of the snow ever fully melting.
- Latitude: Matanuska Glacier is located at 61.6° North Latitude, much farther away from the equator than most any location you might visit within North America. Thus, the winters here are longer and average temperatures cooler throughout the year. This further allows snow at high elevations to accumulate and compress into beautiful, blue glacier ice.
Source: National Park Service: Common Questions and Myths About Glaciers
The Matanuska Glacier is a large ice flow, 27 miles long and 4 miles wide at the terminus, averaging approximately 2 miles in width.
This glacier is a valley glacier; it exists on a valley floor. The majority of glaciers in Alaska today are smaller alpine glaciers which hang off mountain slopes.
The Matanuska is an active glacier which flows at one foot per day in the summer time. It takes approximately 600 years for the ice to form up-glacier and advance to the terminus.
The ice of an active glacier always moves forward due to gravity; like water in a river, the ice will flow down the valley. When ice melts at a higher rate than snow accumulates, the glacier terminus 'recedes'. (The term 'receding' does not refer to the ice actually traveling back up the valley.)
A frequently asked question concerns the cause of the blue ice. The density of glacier ice allows the entire spectrum of light to be absorbed with the exception of the blue light which is reflected and can, therefore, be seen by your eye.
Moraine: Debris (including large boulders, gravel, and sand) that has been deposited by the glacier in various ways.
Lateral: Lining both sides of the glacier, lateral moraines run parallel to ice flow. Lateral moraines are generally created by two processes:
1) a build-up of debris between the sides of the glacier and the bases of surrounding mountains from rock slides off the mountain
2) the dumping of rocks and other debris off the sides of the ice.
Medial: Created as two ice flows merge. As the glaciers meet, a pile of debris is pushed up in between them. The medial moraine may be recognized as a 'ribbon' of black material running down the center of the glacier.
End or Recessional: The terminus (or end) of the glacier is marked by this moraine. Generally lying perpendicular to ice flow, the
end moraine is created as the ice melts and deposits rock and debris.
Vent: An opening in the ice through which water exits the glacier, draining the sub-glacier and en-glacial conduits. The sub-glacial water discharged from this vents is occasionally supercooled (in a liquid state although the temperature is below the freezing point), leading to 'Vrazil' ice growth, and formation of terraces and rims surrounding vents.
Basal Ice: The debris-rich ice layer at the bottom of the glacier. This ice is easily visible in several places at the terminus. Most sediment comprising the moraines is first transported in the basal ice.
Debris Flow: A small-scale avalanche of rock, debris, and water.
Moulin: A wide vertical shaft connecting the ice surface to the glacial conduit system. Moulins are created by meltwater and can be hundreds of feet deep.
Crevasse: A large crack in the ice that may be up to several hundred feet deep and several feet wide, caused by differential speeds in the ice movement.
Serac: Large, towering blocks of ice. Also created by differential speed in ice movement.