Glacier National Park

Geography and geology

Chief Mountain is an isolated peak on the easternmost boundary of the park.

The park is bordered on the north by Waterton Lakes National Park in Alberta, and the Flathead Provincial Forest and Akamina-Kishinena Provincial Park in British Columbia. To the west, the north fork of the Flathead River forms the western boundary, while its middle fork is part of the southern boundary. The Blackfeet Indian Reservation provides most of the eastern boundary, and the Lewis and Clark and the Flathead National Forests form the southern and western boundary. The remote Bob Marshall Wilderness Complex is located in the two forests immediately to the south.

The park contains a dozen large lakes and 700 smaller ones, but only 131 lakes have been named. Lake McDonald, St. Mary Lake, Bowman Lake and Kintla Lake are the four largest lakes. Numerous smaller lakes, known as tarns, are located in cirques formed by glacial erosion. Some of these lakes, like Avalanche Lake and Cracker Lake, are colored an opaque turquoise by suspended glacial silt, which also causes a number of streams to run milky white. The lakes of Glacier National Park remain cold year round, with temperatures rarely above 50 °F (10 °C) at their surface. Cold water lakes such as these support little plankton growth, ensuring that the lake waters are remarkably clear. The lack of plankton, however, lowers the rate of pollution filtration, and pollutants have a tendency to linger longer. Consequently, the lakes are considered environmental "bellweathers" as they can be quickly affected by even minor increases in pollutants.[13]

Two hundred waterfalls are scattered throughout the park, however, during dryer times of the year, many of these are reduced to a trickle. The largest falls include those in the Two Medicine region, McDonald Falls in the McDonald Valley and Swiftcurrent Falls in the Many Glacier area, which is easily observable and close to the Many Glacier Hotel. One of the tallest waterfalls is Bird Woman Falls, which drops 492 feet (150 m) from a hanging valley beneath the north slope of Mount Oberlin.[14] Bird Woman Falls can be easily seen from the Going-to-the-Sun Road.

The rocks found in the park are primarily sedimentary in origin, having been laid down in shallow seas over 1.6 billion to 800 million years ago. During the formation of the Rocky Mountains the Lewis Overthrust, commencing 170 million years ago, moved an enormous region of rocks three miles (4.8 km) thick and 160 miles (257 km) long, eastward more than 50 miles (80 km).[15] This resulted in older rocks being displaced over newer ones, and today the overlying Proterozoic rocks are over 1.4 billion years older than the underlying Cretaceous age rocks.

Landsat 7 image of Waterton-Glacier International Peace Park. The Rocky Mountain Front formed by the Lewis Overthrust fault rises dramatically above the Great Plains on the right.

One of the most dramatic evidences of this overthrust is visible in the form of Chief Mountain, an isolated peak on the edge of the eastern boundary of the park rising 4,500 feet (1,372 m) above the Great Plains. There are seven mountains in the park over 10,000 feet (3,048 m) in elevation, with Mount Cleveland at 10,466 feet (3,190 m) being the tallest. Appropriately named Triple Divide Peak sends waters towards the Pacific Ocean, Hudson Bay, and Gulf of Mexico watersheds, and can effectively be considered to the be the apex of the North American continent, although the mountain is only 8,020 feet (2,444 m) above sea level.

The rocks in Glacier National Park are the best preserved Proterozoic sedimentary rocks in the world, and have proved to be some of the world's most fruitful sources for records of early life. Sedimentary rocks of similar age located in other regions have been greatly altered by mountain building and other metamorphic changes, and consequently fossils are less common and more difficult to observe. The rocks in the park preserve such features as millimeter-scale lamination, ripple marks, mud cracks, salt-crystal casts, raindrop impressions, oolites and other sedimentary bedding characteristics. Six fossilized species of Stromatolites, which were early organisms consisting primarily blue-green algae, have been documented and dated at about 1 billion years.[16] The discovery of the Appekunny Formation, a well preserved rock stratum in the park, pushed back the established date for the origination of animal life a full billion years. This rock formation has bedding structures which are believed to be the remains of the earliest identified metazoan (animal) life on Earth.[17]

Glaciers

Glacier National Park is dominated by mountains which were carved into their present shapes by the huge glaciers of the last ice age; these glaciers have largely disappeared over the 15,000 years. Evidence of widespread glacial action is found throughout the park in the form of U-shaped valleys, glacial cirques, arêtes and large outflow lakes radiating like fingers from the base of the highest peaks. Since the end of the ice ages, various warming and cooling trends have occurred. The last recent cooling trend was during the Little Ice Age which took place approximately between 1550 and 1850.[18] During the Little Ice Age, the glaciers in the park expanded and advanced, although to nowhere near as great an extent as they had during the Ice Age. Coincidentally, the park region was first explored in detail near the end of the Little Ice Age and a systematized survey began in which the number and size of glaciers was documented on maps and by photographic evidence. Much of this late 19th century work, however, was undertaken to lure tourism into the region or to search for mineral wealth, not out of a particular desire to document glaciers.

During the middle of the 20th century, examination of the maps and photographs from the previous century provided clear evidence that the 150 glaciers known to have existed in the park a hundred years earlier had greatly retreated, and in many cases disappeared altogether.[19] Repeat photography of the glaciers, such as the pictures taken of Grinnell Glacier between 1938 and 2005 as shown, help to provide visual confirmation of the extent of glacier retreat.

1938 1981 1998 2005

In the 1980s, the U.S. Geological Survey began a more systematic study of the remaining glaciers, which continues to the present day. By 2005, only 27 glaciers remained, and scientists generally agree that if the current greenhouse warming continues, all the glaciers in the park will be gone by 2030.[19] This glacier retreat follows a worldwide pattern that has accelerated even more since 1980. The extensive glacier retreat that has been observed in Glacier National Park, as well as in other regions worldwide, is a key indicator of climatic changes on a worldwide scale. Without a major climatic change in which cooler and moister weather returns and persists, the mass balance (accumulation rate versus melting rate) of glaciers will continue to be negative and the glaciers will eventually disappear, leaving behind only barren rock.[19]

After the end of the Little Ice Age in 1850, the glaciers in the park retreated moderately until the 1910s. Between 1917 and 1926, the retreat rate rose rapidly and continued to accelerate through the 1930s. A slight cooling trend from the 1940s until 1979, helped to slow the rate of retreat and in a few examples some glaciers even advanced a few tens of meters. However, during the 1980s, the glaciers in the park began a steady period of loss of glacial ice, which continues into the 2000s. In 1850, the glaciers in the region near Blackfoot and Jackson Glaciers covered 5,337 acres (21.6 km²), but by 1979, the same region of the park had glacier ice covering only 1,828 acres (7.4 km²). Between 1850 and 1979, 73 percent of the glacial ice had melted away.[20] At the time the park was created, Jackson Glacier was part of Blackfoot Glacier, but the two separated into different glaciers by 1939.

The impact of glacier retreat on the park's ecosystems is not fully known, but cold water dependent plant and animal species could suffer due to a loss of habitat. Reduced seasonal melting of glacial ice may also affect stream flow during the dry summer and fall seasons, reducing water table levels and increasing the risk of forest fires. The loss of glaciers will also reduce the aesthetic visual appeal that glaciers provide to visitors.[21]

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