Fountain Bluff
From Wikipedia, the free encyclopedia
| Fountain Bluff | |
|---|---|
 Grand Tower Energy Center viewed from the Missouri side of the Mississippi River, with Fountain Bluff behind it. | |
| Highest point | |
| Elevation | 779 ft (237 m)[1] |
| Prominence | 419 ft (128 m)[1] |
| Isolation | 6.26 mi (10.07 km)[1] |
| Coordinates | 37°40′53″N 89°30′26″W / 37.68139°N 89.50722°W[2] |
| Geography | |
  Fountain Bluff Location of Fountain Bluff in Illinois | |
| Location | Jackson County, Illinois, United States |
| Climbing | |
| Access | Happy Hollow Road off IL 3 |
Fountain Bluff is a large, isolated range of hills located in the floodplain of the Mississippi River, on the river's east bank in Fountain Bluff Township, Illinois. Its unusual geographic location was a result of glaciation during the previous Ice Age. It is known for its high steep sandstone cliffs along the river, its biodiversity and abundant Native American rock art.
Fountain Bluff is named for the numerous natural springs within its hills. There is also a large spring called the "Fountain" on the north side of the hills.[3] Fountain Bluff is sometimes called Big Hill by locals with the name "Fountain Bluff" referring to the sandstone cliffs themselves.[4]
Fountain Bluff is located in western Jackson County between the Illinois towns of Gorham to the north and Grand Tower to the south, and across the river from Wittenberg, Missouri. Tower Rock, a major Mississippi River landmark, is also located nearby. Here, the Mississippi River is squeezed into a narrow channel between Fountain Bluff and the Missouri shore, where it forms bedrock rapids. During an 1864 survey the range from low to high water was determined to be 44 feet (13 m).[5]: 67 The 478 megawatt Grand Tower Energy Center is located next to the Mississippi River at the base of Fountain Bluff. The hill is part of the Shawnee National Forest with the exception of a small portion of private property.
The hill is about 4 miles (6.4 km) long and up to 1.5 miles (2.4 km) wide, covering 3,800 acres (1,500 ha). The highest elevation on Fountain Bluff is 779 feet (237 m) near the north end, which is more than 400 feet (120 m) above the level of the Mississippi River valley.[1] Illinois Route 3 follows an alignment along the eastern edge of Fountain Bluff; the Big Muddy River, a tributary of the Mississippi, flows a short distance to the east.[6] A fire tower, open to the public, was long located on the summit and offered "a far-flung view of Illinois and Missouri, of the hills and the river, the fields, forests and farms of the vast bottom lands."[7] As of 1985, the tower was reported to have been dismantled.[8]
In the 1939 Illinois: A Descriptive and Historical Guide Fountain Bluff is described as a "freak formation... which juts from the level flood plain like a huge loaf on a table top."[7] The west and south sides of Fountain Bluff are flanked by sandstone cliffs 70 to 80 feet (21 to 24 m) high.[8] The rest consists of wooded hills interspersed with large rock formations: "some sections are as smooth as polished ivory; others are rough and fissured. Large expanses are covered with lichens, moss and small-leaved vines."[7] The area is dotted with small streams, waterfalls and natural springs, and many caves and rock shelters are formed in the exposed sandstone.[7] There are two named streams flowing from the summit: Trestle Hollow and Happy Hollow.[6]
Due to its geographic isolation (despite its relatively low topographic prominence, it can be considered a minor sky island), the Fountain Bluff has been described as a "refugium for an assemblage of uncommon plants and animals". The northern harebell (Campanula rotundifolia) has been recorded to grow here, far south of its normal range; it may have become established here during the Wisconsinian glaciations.[9] Mohlenbrock (1975) recorded a total of 991 taxa of plants.[8] The major plant communities on Fountain Bluff are found in floodplain woods/swamps, "limestone woods" (established on shallow soil over limestone), mesic woods, "hill prairies" at exposed summits, and cliff faces.[8]
Geology
Although it is located east of the Mississippi River, Fountain Bluff was once part of the west bank of the Mississippi valley. During the Wisconsinian Ice Age period from 85,000–11,000 years ago, the Cordilleran Ice Sheet advanced over much of North America and blocked the main channel of the Mississippi River. Swollen with glacial meltwater, the Mississippi River was forced to rise and carve a new channel to the west. When the ice sheet retreated, Fountain Bluff was left as an isolated "island" in the middle of the valley. During periods of heavy glacial melt, Fountain Bluff would have been a true island surrounded with water on all sides.[10]: 232–233 After the ice was gone, the Mississippi may have changed course multiple times to flow around the west or east sides of Fountain Bluff, although it is currently locked in the deeper western channel.[7] The Big Muddy River flows through the original Mississippi valley to the east as an underfit stream.[11]
The west and south edges of Fountain Bluff consists of exposed rock bluffs created by erosion from the Mississippi River. The hills are composed of Upper Chesterian limestone overlaid by Lower Pennsylvanian (Caseyville Formation) sandstone.[12][13] Sandstone comprises most of the exposed (visible) strata.[14] A smaller sandstone formation known as the "Devil's Bake Oven", which includes a natural arch, is located downstream and was formed from the same rock and glacial action that created Fountain Bluff.[15] Two fault zones, the Pomona to the north and the Rattlesnake Ferry to the south, cross the area.[10]