Geography and geology
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. Immediately to the south is the remote Bob Marshall Wilderness Complex.Only 131 of the parks dozen large lakes and 700 smaller ones 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. With temperatures rarely above 50 °F (10 °C) at their surface, the lakes of Glacier National Park remain cold year round. 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. Minor increases in pollutants quickly affect the lakes, hence they are considered environmental bellwethers.
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. Bird Woman Falls can be easily seen from the Going-to-the-Sun Road.
Having been laid down in shallow seas over 1.6 billion to 800 million years ago the rocks in the park are mostly sedimentary in origin. 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). 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.
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 best 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 have preserved such features as millimeter-scale lamination, ripple marks, mud cracks, salt-crystal casts, raindrop impressions and other sedimentary bedding characteristics. Six fossilized species of Stromatolites, early organisms consisting of primarily blue-green algae, have been documented and dated at about 1 billion years. A well preserved rock stratum in the park, the discovery of the Appekunny Formation, pushed back the established date for the origination of animal life a full billion years. This rock formation has bedding structures that are believed to be the remains of the earliest identified metazoan (animal) life on Earth.
