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Glacier National Park Glaciers: Past, Present and Future
Glacier National Park is located in the northwest corner of Montana, and is well known for its numerous alpine glaciers that are found throughout the park. Much of the focus lately has been the rate of melting that is occurring with these Glacier National Park glaciers, so I just wanted to write an article that discusses Glacier National Park glaciers in general, and the history of these iconic masses of ice and snow. I have always been extremely interested in the geology and glaciation of Glacier National Park. In fact, in college I studied geophysics and geology for over three years prior to switching directions and instead becoming a Doctor of Optometry.
Glacier National Park’s Name-Sake
The incredible landscape that you presently see at Glacier National Park for the most part has nothing to do with the present alpine glaciers that rest on the northern and eastern slopes of the park’s mountains. Rather, the mountains and valleys of Glacier National Park were sculpted by massive glaciers known as “valley glaciers” over ten thousand years ago during the last major Ice Age. These gigantic valley glaciers acted as giant bull-dozers that excavated the land, creating deep U-shaped valleys and incredible mountainous landscapes. These massive glaciers were nearly 6,000 feet thick, and as they moved downward due to gravity, they cut and formed the rock like a knife on butter. This created deep valleys with incredibly tall vertical walls on each side. Once these valley glaciers melted away nearly 10,000 years ago, today’s world-renowned landscape of Glacier National Park was the result.
Glacier National Park was named after this unbelievable excavation by these monstrous valley glaciers of the last Ice Age. Absolutely every square inch of Glacier National Park shows obvious remnants of this amazing glacial event, which serves as a textbook example of the effects of glaciation for all to see.
Besides the deep U-shaped valleys, these valley glaciers created classic examples of ice age glaciation, such as matterhorns (a.k.a. horns). There are many classic examples of horns in Glacier National Park, such as Reynolds Mountain and Flinsch Peak. These peaks rise thousands of feet into the sky with nearly straight up and down walls on all sides, leaving a very small summit. Horns are a result of three (and sometimes four) valley glaciers cutting away the rock on each side of the mountain, leaving only a very tall, narrow mountain that looks almost like a tower once the glaciers melt away.
Another common formation found after the valley glaciers of Glacier National Park did their work are what is known as aretes. Aretes are long and extremely narrow ridges, that seem to be almost paper-thin. A classic example of an arete in Glacier National Park is the famous Garden Wall which is found near Logan Pass along the Going To The Sun Road. Aretes are created by two valley glaciers that are located side-by-side. All that is left after these massive rivers of ice melt away are these extremely narrow ridges that are thousands of feet high.
Yet another formation that is a classic sign of glaciation, are what is known as cirques. Cirques are basically huge “amphitheaters” created by incredibly large glaciers that scoured out the rock like a giant ice cream scoop. There are hundreds of these cirques found throughout the park, and many of them ended up being the home to the smaller alpine glaciers that came into the seen after the colossal Glacier National Park glaciers of the most recent ice age retreated.
Valley glaciers are known as “rivers of ice” because they actually flow like a river down the valley due to gravity. The endless cycle of melting and re-freezing occurs over and over again at the bottom of the glacier (known as the foot), and this action acts like a conveyer belt that piles this rock debris into what’s called a glacial moraine. These moraines resemble large gravel piles, and if you look closely you’ll see all sizes of rocks within these moraines… some rocks being the size of a house, others the size of a small pebble.
Today’s Alpine Glaciers of Glacier National Park
Glacier National Park glaciers of today are distant cousins of the great valley glaciers of the past ice ages. Known as “Alpine Glaciers”, these smaller glaciers formed approximately 7,000 years ago, where many of them appeared in the large cirques that were previous excavated during the last ice age. These small alpine glaciers developed in and around the 8,000 foot elevation mark, and are most commonly found hugging the north or east slopes of the cirques. The 8,000 foot elevation is where most of the snow accumulates in these cirques, and the north and/or east slopes receives the least amount of direct sunlight. Huge amounts of drifting snow due to the high winds of winter also seem to accumulate the most at the 8,000 foot level. Any higher in elevation, the snow is blown off the slopes due to these high winds, and also the rock walls are often too steep to hold snow once you get beyond about 8,300 feet.
These alpine glaciers act as “ice cream scoops” as they cut away the rock as they slowly slide downhill due to gravity. And through the endless cycle of melting and freezing at the foot of these glaciers, glacial moraines are found at the base of all of these glaciers. Some of the rock is ground so small that glacier silt is formed, which is known as “glacial flour”. This glacial silt ends up suspended in streams and lakes, which results in the amazing turquoise color of many of the lakes in Glacier National Park, such as Grinnell Lake and Cracker Lake.
As these glaciers melt during the warmer months each year, the water from this melting is extremely cold as it flows into the streams, rivers and lakes of Glacier National Park, making it very conducive to many forms of cold water aquatic life, such as the native bull trout.
The rock excavation from these small alpine glaciers are a small fraction of the tremendous excavation of the ice age glaciers. It’s like comparing a tiny Tonka toy truck to a giant bulldozer. There really is no comparison. But even though these alpine glaciers do little to shape the landscape, they are still part of an important process in the ecosystem of Glacier National Park.
The Future of Alpine Glaciers in Glacier National Park
The present day Glacier National Park Glaciers have been shrinking at least since the Civil War, and will more than likely keep shrinking until they are no longer considered to be true glaciers. According to the most recent research, Glacier National Park had 150 alpine glaciers in 1850, and now there are only 25 active glaciers. And what is meant by “active” is that the glacier is moving and cutting rock.
One thing that somewhat muddies the water is that the “definition of a glacier” has changed through the years. Presently, the USGS Climate Change in Mountain Ecosystems Program has established the definition of a glacier as a moving mass of snow, rock, ice and water that is at least 25 acres in size and 100 feet thick. This wasn’t the definition of glaciers in 1850, so there is a bit of a discrepancy occurring here. But the overall picture hasn’t changed and one that has been quite consistent, and that is the fact that these alpine glaciers have been shrinking since the Civil War in the mid 1800s, and are continuing to shrink in size as we speak.
An example of a glacier that has been demoted, even though its size had not changed, is Gem Glacier. Gem Glacier is located above the Grinnell Glacier in the Many Glacier Area of Glacier National Park, and it rests on a huge vertical wall on a small shelf. Gem Glacier looks the same now as it does in the photos of the late 1800’s, but since it is not 25 acres in size (and never has been), Gem Glacier does not fit the modern definition of a glacier and was therefore demoted.
A great example of an “expired” glacier is the snow mass directly below Clements Mountain on Logan Pass. As you hike up the trail to Hidden Lake Overlook, you will see a giant glacial moraine directly to your right, which is located just below the east base of Clements Mountain. If you hike to the top of the moraine, you will see a giant snow field between the moraine and the base of the mountain. This was an active glacier until the 1930’s, when it stopped moving due to its shrinking size. It is now simply a large, permanent snow field.
Once a glacier is no longer heavy enough to be moved by gravity, it is no longer considered a glacier. It is then called a permanent snow field or permanent ice field. My wife Shannon and I climbed over 130 summits in Glacier National Park through the years, and we have explored nearly all of the backcountry regions of Glacier National Park. We’ve observed every location where the retired glaciers are found, and what is now mainly in their place are permanent snow and ice fields. Actually there are a few locations where the snow fields disappear completely by late September of each year, but re-appear during the late fall and winter as the snow begins to fall. These snow fields once again slowly melt into the streams, rivers and lakes until they disappear again in late September of the following year.
Glacier National Park receives a TON of seasonal snowfall each autumn, winter and spring, and a fair amount of this snow really piles up in certain areas throughout the higher elevations…especially where there were once alpine glaciers. This creates massive snow fields that quite often survive until late September, if not all year long. That’s actually how all of the mountains of the Rockies operate. The Rockies receive a lot of snow during the fall, winter and spring, and this snow slowly melts through the 3 months of summer, feeding the streams, rivers and lakes with this water. This cycle of seasonal snow fall repeats itself year after year, and is mainly what feeds the streams, rivers and lakes of the Rocky Mountains.
Glacier National Park is a great place to observe the effects of colossal glaciation that occurred over ten thousand years ago during a series of ice ages, and is also a fantastic place to observe the ever-changing alpine glaciers that are found throughout the park. Glacier National Park glaciers are fascinating to see and to discover, and I highly recommend that you come to Glacier National Park to witness them first-hand… The landscape and the grandeur of this amazing place will help you’ll quickly understand why Glacier National Park is known as “The Crown of the Continent”.
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