Flathead Lake

Infobox_lake
lake_name = Flathead Lake
image_lake = Flathead Lake.jpeg
caption_lake =
image_bathymetry = FLBathymetricMap.jpg
caption_bathymetry = Bathymetric Map
coords = coord|47|54|6|N|114|6|15|W|region:US-MT_type:waterbody|display=inline,title
location= Montana
type = Moraine-dammed lake
inflow = Flathead River
Swan River
outflow = Flathead River
catchment = convert|8587|sqmi|abbr=on
basin_countries = United States
length = convert|27.3|mi|abbr=on
width = convert|15.5|mi|abbr=on
area = convert|191.5|sqmi|abbr=on
depth = convert|164.7|ft|abbr=on
max-depth = convert|370.7|ft|abbr=on
volume = convert|5.56|cumi|km3|abbr=on
shore = convert|161.4|mi|abbr=on
elevation = convert|2894|ft|abbr=on
residence_time= 3.4 years
islands = Wildhorse Island, Bird Island
cities =

Flathead Lake is the largest lake in the western part of the coterminous United States, surpassing Nevada/California's Lake Tahoe by .5 miles in surface area, 5 miles in length, and about 3.5 miles in width, "Flathead Lake" is also the largest lake in the state of Montana. This lake is one of the cleanest in the world for its size and type. [http://www.flatheadlakers.org/flathead_lake_basin/overview.html] [http://www.umt.edu/flbs/AboutFLBS/FlatheadLake.htm] While the Great Salt Lake is technically larger than Flathead Lake, the former is a natural salt lake or "inland sea" while Flathead Lake is a freshwater lake.

Located in the northwest corner of the state, 7 miles (11 km) south of Kalispell, it is approximately 30 miles (50 km) long and 16 miles (25 km) wide, covering 191.5 square miles (495.9 km²). Flathead Lake is 30 miles (48 km) southwest of Glacier National Park and is flanked by two scenic highways, which wind along its curving shoreline. On the west side is US Highway 93, and on the east, is Route 35.The lake is bordered on its eastern shore by the Mission Mountains and on the west by the Salish Mountains. The Flathead valley was formed by the glacial damming of the Flathead River and sustains a remarkably mild climate for a region located this far north. Once known as "Salish Lake", this body of water takes its name from the Salish (Flathead) Indians who live at the southern end of the lake on the Flathead Indian Reservation. Kerr Dam, near Polson, regulates the lake's water level and provides hydroelectric power and water for irrigation. The lake has an irregularly-shaped shoreline and several small islands, the largest of which is a state park called Wild Horse Island. These islands cover 5.5 square miles (14.2 square kilometers). Besides the Flathead River, the Swan River is the lake's other major tributary. The lake is inhabited by the native bull trout and cutthroat trout, as well as the non-native lake trout, yellow perch, and lake whitefish. It is also reportedly inhabited by the infamous Flathead Lake Monster.

Geology

Flathead Lake lies at the end of a geological feature called the Rocky Mountain Trench. The trench, which formed with the Rocky Mountains roughly 60 million years ago, extends north into the southern Yukon as a straight, steep valley, which also holds the headwaters of the Columbia River. During the last ice age this trench was filled by an enormous glacier. As the glacier moved southward it carved out the trench. Present day Polson, Montana marks the southernmost extent of the glacier during the last ice age and thus is the site of the glacier's terminal moraine.

The large size of the Polson Moraine indicates that the glacier stalled here for several years before retreating. As the climate warmed, a portion of the glacier in the Mission Valley receded more slowly than the main body, which kept the lake basin from being filled with sediment. Eventually this ice also melted, forming a lake behind the moraine. Once the water reached the top of this moraine dam, it began to cut a channel through it. Most moraine dammed lakes drain quickly because water cuts entirely through the moraine. However, Flathead Lake remains because a bedrock hill buried underneath the Polson Moraine prevented the moraine from being completely cut through so the meltwater never completely drained.

References

* Alt, David. "The Making of Flathead Lake" in Profiles of Montana Geology: A layman's guide to the Treasure State. Butte, MT: Montana Bureau of Mines and Geology, 1984
* Flathead Lake Biological Station. "About Flathead Lake." Available at http://www.umt.edu/flbs/aboutflbs/flatheadlake.htm
* [http://www.flatheadlakers.org Flathead Lakers]
* [http://watersheds.montana.edu/groups/details.asp?groupID=21 Montana Watersheds - Flathead Basin]

External links

* [http://www.umt.edu/flbs/ Flathead Lake Biological Station]