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89-702: The Mountain Lake Wilderness Cluster contains wildlands under different levels of management. There are wilderness areas protected by Congressional action, inventoried wilderness , areas recognized by Wilderness Society as worthy of protection from timbering and roads, and other forest service land that act as a buffer for the protected areas. These areas are in the Jefferson National Forest . In addition, there are privately owned lands managed to maintain their wild character or serve as an environment for study, and land operated by

178-400: A (usually small) angle. Sometimes multiple sets of layers with different orientations exist in the same rock, a structure called cross-bedding . Cross-bedding is characteristic of deposition by a flowing medium (wind or water). The opposite of cross-bedding is parallel lamination, where all sedimentary layering is parallel. Differences in laminations are generally caused by cyclic changes in

267-424: A diagenetic structure common in carbonate rocks is a stylolite . Stylolites are irregular planes where material was dissolved into the pore fluids in the rock. This can result in the precipitation of a certain chemical species producing colouring and staining of the rock, or the formation of concretions . Concretions are roughly concentric bodies with a different composition from the host rock. Their formation can be

356-659: A good means to reach the lake. A tour through the cluster is obtained by continuing along Va 613 to the point where it begins to ascend Peters Mountain. At this point, the road, called the Salt Sulphur Turnpike, deteriorates as it ascends Peters Mountain. The present condition of the Peters Mountain section is probably similar to the days when it was traveled by stage. The road is now best used by high-clearance 4-wheel drive vehicles, hikers, mountain bikers, and horseback riders. The Appalachian Trail and

445-527: A lake. The lake is unique with its geology , hydrology , possession of a fault and colluvium , as well as high aquatic species diversity . This combination of features is possessed by few if any other lakes in the world. The first recorded sighting of Mountain Lake by a westerner was by Christopher Gist in 1751. In 1884 W. B. Rogers conducted the first geological study of the lake. He observed that trees and shrubs were seen at considerable depth, attesting to

534-568: A non-profit organization, the Mountain Lake Conservancy. Among the areas included in the Wilderness Cluster are: The Mountain Lake Wilderness Cluster is located in southwestern Virginia, near Pembroke, Virginia. The heart of the area is Mountain Lake , the only natural body of water in western Virginia. The original route to Mountain Lake was a turnpike completed in 1859 that followed the present VA 700 to

623-463: A particular sedimentary environment. Examples of bed forms include dunes and ripple marks . Sole markings, such as tool marks and flute casts, are grooves eroded on a surface that are preserved by renewed sedimentation. These are often elongated structures and can be used to establish the direction of the flow during deposition. Ripple marks also form in flowing water. There can be symmetric or asymmetric. Asymmetric ripples form in environments where

712-465: A red colour does not necessarily mean the rock formed in a continental environment or arid climate. The presence of organic material can colour a rock black or grey. Organic material is formed from dead organisms, mostly plants. Normally, such material eventually decays by oxidation or bacterial activity. Under anoxic circumstances, however, organic material cannot decay and leaves a dark sediment, rich in organic material. This can, for example, occur at

801-489: A rock is usually expressed with the Wentworth scale, though alternative scales are sometimes used. The grain size can be expressed as a diameter or a volume, and is always an average value, since a rock is composed of clasts with different sizes. The statistical distribution of grain sizes is different for different rock types and is described in a property called the sorting of the rock. When all clasts are more or less of

890-465: A sediment after its initial deposition. This includes compaction and lithification of the sediments. Early stages of diagenesis, described as eogenesis , take place at shallow depths (a few tens of meters) and is characterized by bioturbation and mineralogical changes in the sediments, with only slight compaction. The red hematite that gives red bed sandstones their color is likely formed during eogenesis. Some biochemical processes, like

979-463: A sedimentary rock are called sediment , and may be composed of geological detritus (minerals) or biological detritus (organic matter). The geological detritus originated from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement , which are called agents of denudation . Biological detritus

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1068-431: A sedimentary rock may have been present in the original sediments or may formed by precipitation during diagenesis. In the second case, a mineral precipitate may have grown over an older generation of cement. A complex diagenetic history can be established by optical mineralogy , using a petrographic microscope . Carbonate rocks predominantly consist of carbonate minerals such as calcite, aragonite or dolomite . Both

1157-516: A small-scale property of a rock, but determines many of its large-scale properties, such as the density , porosity or permeability . The 3D orientation of the clasts is called the fabric of the rock. The size and form of clasts can be used to determine the velocity and direction of current in the sedimentary environment that moved the clasts from their origin; fine, calcareous mud only settles in quiet water while gravel and larger clasts are moved only by rapidly moving water. The grain size of

1246-639: A state by state basis and determines which areas and how much land in each area will become part of the WPS. There have been multiple occasions in which Congress designated more federal land than had been recommended by the nominating agency. Where as the Wilderness Act stipulated that a wilderness area must be "administered for the use and enjoyment of the American people in such a manner as will leave them unimpaired for future use and enjoyment as wilderness",

1335-952: A term for a fissile mudrock (regardless of grain size) although some older literature uses the term "shale" as a synonym for mudrock. Biochemical sedimentary rocks are created when organisms use materials dissolved in air or water to build their tissue. Examples include: Chemical sedimentary rock forms when mineral constituents in solution become supersaturated and inorganically precipitate . Common chemical sedimentary rocks include oolitic limestone and rocks composed of evaporite minerals, such as halite (rock salt), sylvite , baryte and gypsum . This fourth miscellaneous category includes volcanic tuff and volcanic breccias formed by deposition and later cementation of lava fragments erupted by volcanoes, and impact breccias formed after impact events . Alternatively, sedimentary rocks can be subdivided into compositional groups based on their mineralogy: Sedimentary rocks are formed when sediment

1424-417: A texture, only the average size of the crystals and the fabric are necessary. Most sedimentary rocks contain either quartz ( siliciclastic rocks) or calcite ( carbonate rocks ). In contrast to igneous and metamorphic rocks, a sedimentary rock usually contains very few different major minerals. However, the origin of the minerals in a sedimentary rock is often more complex than in an igneous rock. Minerals in

1513-425: A valuable indicator of the biological and ecological environment that existed after the sediment was deposited. On the other hand, the burrowing activity of organisms can destroy other (primary) structures in the sediment, making a reconstruction more difficult. Secondary structures can also form by diagenesis or the formation of a soil ( pedogenesis ) when a sediment is exposed above the water level. An example of

1602-503: Is deposited out of air, ice, wind, gravity, or water flows carrying the particles in suspension . This sediment is often formed when weathering and erosion break down a rock into loose material in a source area. The material is then transported from the source area to the deposition area. The type of sediment transported depends on the geology of the hinterland (the source area of the sediment). However, some sedimentary rocks, such as evaporites , are composed of material that form at

1691-421: Is a structure where beds with a smaller grain size occur on top of beds with larger grains. This structure forms when fast flowing water stops flowing. Larger, heavier clasts in suspension settle first, then smaller clasts. Although graded bedding can form in many different environments, it is a characteristic of turbidity currents . The surface of a particular bed, called the bedform , can also be indicative of

1780-409: Is called bedding . Single beds can be a couple of centimetres to several meters thick. Finer, less pronounced layers are called laminae, and the structure a lamina forms in a rock is called lamination . Laminae are usually less than a few centimetres thick. Though bedding and lamination are often originally horizontal in nature, this is not always the case. In some environments, beds are deposited at

1869-471: Is estimated to be only 8% of the volume of the crust. Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks . Sedimentary rocks are deposited in layers as strata , forming a structure called bedding . Sedimentary rocks are often deposited in large structures called sedimentary basins . Sedimentary rocks have also been found on Mars . The study of sedimentary rocks and rock strata provides information about

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1958-429: Is higher when the sedimentation rate is high (so that a carcass is quickly buried), in anoxic environments (where little bacterial activity occurs) or when the organism had a particularly hard skeleton. Larger, well-preserved fossils are relatively rare. Fossils can be both the direct remains or imprints of organisms and their skeletons. Most commonly preserved are the harder parts of organisms such as bones, shells, and

2047-491: Is mirrored by the broad categories of rudites , arenites , and lutites , respectively, in older literature. The subdivision of these three broad categories is based on differences in clast shape (conglomerates and breccias), composition (sandstones), or grain size or texture (mudrocks). Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel. Sandstone classification schemes vary widely, but most geologists have adopted

2136-401: Is reduced. Sediments are typically saturated with groundwater or seawater when originally deposited, and as pore space is reduced, much of these connate fluids are expelled. In addition to this physical compaction, chemical compaction may take place via pressure solution . Points of contact between grains are under the greatest strain, and the strained mineral is more soluble than the rest of

2225-493: Is the most stable, followed by feldspar , micas , and finally other less stable minerals that are only present when little weathering has occurred. The amount of weathering depends mainly on the distance to the source area, the local climate and the time it took for the sediment to be transported to the point where it is deposited. In most sedimentary rocks, mica, feldspar and less stable minerals have been weathered to clay minerals like kaolinite , illite or smectite . Among

2314-664: Is under federal ownership and management, (2) the area consists of at least five thousand acres of land, (3) human influence is "substantially unnoticeable," (4) there are opportunities for solitude and recreation, and (5) the area possesses "ecological, geological, or other features of scientific, educational, scenic, or historical value." Wilderness areas are subject to specific management restrictions; human activities are limited to non-motorized recreation (such as backpacking , camping , hunting , fishing , horseback riding, etc.), scientific research , and other non-invasive activities. During these activities, patrons are asked to abide by

2403-825: The Allegheny Trail pass through the cluster. Access to the Appalachian Trail is gained at road crossings in Johns Creek Road (Va 632), Mountain Lake Road (Va 613), and Big Stony Creek Rd (Va 635). There are no road crossing of the Allegheny Trail, but it can be reached by parking on North Fork Mountain Road (Va 613), then hiking along the old turnpike to reach the trail where it passes along the ridge of Peters Mountain. There are 18 trails on

2492-649: The Bureau of Land Management . The term wilderness is defined as "an area where the earth and community of life are untrammeled by man, where man himself is a visitor who does not remain" and "an area of undeveloped Federal land retaining its primeval character and influence, without permanent improvements or human habitation, which is protected and managed so as to preserve its natural conditions". As of 2023 , 806 wilderness areas have been designated, totaling 111,889,002 acres (45,279,873 ha; 452,798.73 km ; 174,826.566 sq mi), which comprise about 4.5% of

2581-591: The Eastern Wilderness Areas Act of 1975, which added 16 national forest areas to the NWPS, allowed for the inclusion of areas that had been severely modified by human interference. The Wilderness Act provides criteria for lands being considered for wilderness designation. Though there are some exceptions, the following conditions must be present for an area to be included in the NWPS: (1) the land

2670-623: The Leave No Trace policy. This policy sets guidelines for using the wilderness responsibly and leaving the area as it was before usage. These guidelines include: Packing all trash out of the wilderness, using a stove as opposed to a fire, camping at least 200 feet (61 m) from trails or water sources, staying on marked trails, and keeping group size small. When closely observed, the Leave No Trace ethos ensures that wilderness areas remain untainted by human interaction. In general,

2759-664: The Pelican Island Wilderness in northern Florida , which measures just 6 acres (2.4 ha) total. The smallest area preserved in the system was formerly the Rocks and Islands Wilderness in Northern California at 5 acres (2.0 ha), but after a reassessment by the Bureau of Land Management in 2006 it was officially expanded to 19 acres (7.7 ha). On November 7, 2009, an agreement between

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2848-809: The Weeks Act was passed in 1911 for the purchase of lands to create an eastern national forest. In 1937 the Jefferson National Forest was dedicated. The Forest Service has managed the land to minimize the effects of commercial operations, such as logging and mining, that would lead to environmental degradation . Other clusters of the Wilderness Society's "Mountain Treasures" in the Jefferson National Forest (north to south): National Wilderness Preservation System The National Wilderness Preservation System ( NWPS ) of

2937-463: The history of life . The scientific discipline that studies the properties and origin of sedimentary rocks is called sedimentology . Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences , such as pedology , geomorphology , geochemistry and structural geology . Sedimentary rocks can be subdivided into four groups based on

3026-463: The land area of the United States . During the 1950s and 1960s, as the American transportation system was on the rise, concern for clean air and water quality began to grow. A conservation movement began to take place with the intent of establishing designated wilderness areas. Howard Zahniser created the first draft of the Wilderness Act in 1956. It took nine years and 65 rewrites before

3115-682: The organic material of a dead organism undergoes chemical reactions in which volatiles such as water and carbon dioxide are expulsed. The fossil, in the end, consists of a thin layer of pure carbon or its mineralized form, graphite . This form of fossilisation is called carbonisation . It is particularly important for plant fossils. The same process is responsible for the formation of fossil fuels like lignite or coal. Structures in sedimentary rocks can be divided into primary structures (formed during deposition) and secondary structures (formed after deposition). Unlike textures, structures are always large-scale features that can easily be studied in

3204-501: The Dott scheme, which uses the relative abundance of quartz, feldspar, and lithic framework grains and the abundance of a muddy matrix between the larger grains. Six sandstone names are possible using the descriptors for grain composition (quartz-, feldspathic-, and lithic-) and the amount of matrix (wacke or arenite). For example, a quartz arenite would be composed of mostly (>90%) quartz grains and have little or no clayey matrix between

3293-708: The Mountain Lake area was a high valley draining to the southwest. A landslide formed a dam blocking the outlet and creating a lake behind the dam. Native Americans, early users of the area as a reserve for hunting and fishing, did not intensely occupy the area, but lived in surrounding lands. The first known settler in the area was recorded on a tombstone, "Mary Porter killed by Indians in 1742". Forts were constructed for protection from Indian raids, but massacres by Indians continued to devastate many Giles county families from 1774 to 1778. The families of early settlers were mostly independent of one another. They lived off

3382-521: The NWPS included 34 areas protecting 9.1 million acres (37,000 km ) in the national forests. As of 2023, there are 806 areas in the NWPS, preserving 111,889,002 acres (45,279,873 ha). This is approximately 4.5% of the entire United States , though only about 2.7% of the 48 contiguous states. However, most of that acreage is located in a handful of states. The states with the highest number of wildernesses are California , Arizona , Nevada , Alaska , and Oregon . However, when measured in acres

3471-747: The NWPS, much of the wildlife in the U.S. also has an area in which to exist without significant human interaction. In late 2011, a full wilderness review was requested of the Arctic Refuge Coastal Plain in Alaska. One of the major qualifications for this area to be considered as a possible wilderness area was its diverse wildlife population, many of which are on the endangered species list. In this potential wilderness area alone, whales , seals , wolves , polar bears , grizzly bears , muskoxen , caribou , and over 200 species of migratory birds call this one area home for at least part of

3560-602: The NWPS. The first national forest wilderness areas were established by the Wilderness Act itself. The Great Swamp in New Jersey became the first National Wildlife Refuge with formally designated wilderness in 1968. Wilderness areas in national parks followed, beginning with the designation of wilderness in part of Craters of the Moon National Monument in Idaho in 1970. A dramatic spike in acreage added to

3649-724: The National Wilderness Preservation System. On March 30, 2009, President Barack Obama signed into law the Omnibus Public Land Management Act of 2009 . The legislation designated an additional 2 million acres (810,000 ha) in nine states as wilderness, representing the largest expansion of wilderness lands since 1994. The John D. Dingell, Jr. Conservation, Management, and Recreation Act of 2019 added another 1.3 million acres (530,000 ha) in 43 new and expanded wilderness areas. On federal lands in

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3738-631: The Potts Valley Branch of the Norfolk and Western arrived. Full service to Waiteville started in 1909. Logging began and most of the trees were removed. Inclined rail technology was used to gain access to steeper slopes. The railroad is now gone and the tracks have been removed, but a remnant of the rail line can be explored by bike or foot on the Potts Mountain Rail Trail. In order to create watershed protection,

3827-476: The United States protects federally managed wilderness areas designated for preservation in their natural condition. Activity on formally designated wilderness areas is coordinated by the National Wilderness Preservation System. Wilderness areas are managed by four federal land management agencies: the National Park Service , the U.S. Forest Service , the U.S. Fish and Wildlife Service , and

3916-464: The United States, Congress may designate an area as wilderness under the provisions of the Wilderness Act of 1964. Multiple agencies, including the Bureau of Land Management , the National Park Service , the Fish and Wildlife Service , and the U.S. Forest Service , are responsible for the submission of new areas that fit the criteria to become wilderness to Congress. Congress then reviews these cases on

4005-532: The United States, Canada, and Mexico entitled the "Memorandum of Understanding on Cooperation for Wilderness Conservation" was made. This agreement created a new entity, the North American Intergovernmental Committee on Cooperation for Wilderness and Protected Areas Conservation, that would streamline the process for open communication between international agencies for the purpose of wilderness preservation. This committee

4094-481: The Wilderness Act was finally passed in 1964. The Wilderness Act of 1964 (Public Law 88-577), which established the NWPS, was signed into law by President Lyndon B. Johnson on September 3, 1964. The Wilderness Act mandated that the National Park Service, U.S. Forest Service, and U.S. Fish and Wildlife Service review all federal lands under their jurisdiction for wilderness areas to include in

4183-470: The activity of bacteria , can affect minerals in a rock and are therefore seen as part of diagenesis. Deeper burial is accompanied by mesogenesis , during which most of the compaction and lithification takes place. Compaction takes place as the sediments come under increasing overburden (lithostatic) pressure from overlying sediments. Sediment grains move into more compact arrangements, grains of ductile minerals (such as mica ) are deformed, and pore space

4272-503: The blight. A large number of hemlock trees are threatened by the woolly adelgid that arrived in 2000. Efforts are underway to introduce beetle predators known to feed on the woolly adelgid. The tawny crescent is a butterfly that is considered endangered and has disappeared from much of its former range in the Appalachians. One of the best known populations was at Mountain Lake. It is severely threatened by spraying intended for

4361-399: The bottom of deep seas and lakes. There is little water mixing in such environments; as a result, oxygen from surface water is not brought down, and the deposited sediment is normally a fine dark clay. Dark rocks, rich in organic material, are therefore often shales. The size , form and orientation of clasts (the original pieces of rock) in a sediment is called its texture . The texture is

4450-504: The cement and the clasts (including fossils and ooids ) of a carbonate sedimentary rock usually consist of carbonate minerals. The mineralogy of a clastic rock is determined by the material supplied by the source area, the manner of its transport to the place of deposition and the stability of that particular mineral. The resistance of rock-forming minerals to weathering is expressed by the Goldich dissolution series . In this series, quartz

4539-421: The cement to produce secondary porosity . At sufficiently high temperature and pressure, the realm of diagenesis makes way for metamorphism , the process that forms metamorphic rock . The color of a sedimentary rock is often mostly determined by iron , an element with two major oxides: iron(II) oxide and iron(III) oxide . Iron(II) oxide (FeO) only forms under low oxygen ( anoxic ) circumstances and gives

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4628-647: The control of gypsy moths . Its habitat is not well known, but is considered to prefer steep, dry, sparsely wooded hillsides. The region is in the Ridge and Valley Province of the Appalachian Mountains . The province consists of a thick layer of sedimentary rock that has undergone folding and/or faulting to create a series of ridges and valleys. During the sedimentation process fossils were formed leaving evidence of life existing millions of years ago. The fossils can be seen in rock exposures throughout

4717-572: The current is in one direction, such as rivers. The longer flank of such ripples is on the upstream side of the current. Symmetric wave ripples occur in environments where currents reverse directions, such as tidal flats. Mudcracks are a bed form caused by the dehydration of sediment that occasionally comes above the water surface. Such structures are commonly found at tidal flats or point bars along rivers. Secondary sedimentary structures are those which formed after deposition. Such structures form by chemical, physical and biological processes within

4806-663: The dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions: gravel (>2 mm diameter), sand (1/16 to 2 mm diameter), and mud (<1/16 mm diameter). Mud is further divided into silt (1/16 to 1/256 mm diameter) and clay (<1/256 mm diameter). The classification of clastic sedimentary rocks parallels this scheme; conglomerates and breccias are made mostly of gravel, sandstones are made mostly of sand , and mudrocks are made mostly of mud. This tripartite subdivision

4895-471: The exact nature of protection may differ from federal laws. Some U.S. states have created wilderness preservation programs modeled on the NWPS. Sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface , followed by cementation . Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form

4984-489: The field. Sedimentary structures can indicate something about the sedimentary environment or can serve to tell which side originally faced up where tectonics have tilted or overturned sedimentary layers. Sedimentary rocks are laid down in layers called beds or strata . A bed is defined as a layer of rock that has a uniform lithology and texture. Beds form by the deposition of layers of sediment on top of each other. The sequence of beds that characterizes sedimentary rocks

5073-404: The flow calms and the particles settle out of suspension . Most authors presently use the term "mudrock" to refer to all rocks composed dominantly of mud. Mudrocks can be divided into siltstones, composed dominantly of silt-sized particles; mudstones with subequal mixture of silt- and clay-sized particles; and claystones, composed mostly of clay-sized particles. Most authors use " shale " as

5162-536: The future of both the U.S. system and North American preservation efforts as a whole. One of the major goals of the Wilderness Preservation System is to provide undeveloped habitats for threatened or endangered species . Many of the species found in the United States are represented in wilderness areas. There are 261 basic ecosystems in the U.S., and 157 of them are represented in the system. With 60% of all ecosystems somewhat protected by

5251-485: The grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact. The increased pressure and temperature stimulate further chemical reactions, such as the reactions by which organic material becomes lignite or coal. Lithification follows closely on compaction, as increased temperatures at depth hasten the precipitation of cement that binds the grains together. Pressure solution contributes to this process of cementation , as

5340-510: The grains, a lithic wacke would have abundant lithic grains and abundant muddy matrix, etc. Although the Dott classification scheme is widely used by sedimentologists, common names like greywacke , arkose , and quartz sandstone are still widely used by non-specialists and in popular literature. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles. These relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as

5429-626: The home to more salamander species than anywhere else in the world. The area's diverse forests and freshwater ecosystems provide a home to these reptiles that have become adapted to cool highlands. Almost half of all these species are listed as threatened or endangered. In the early 20th century the forest was dominated by chestnut trees to the extent that the forest was characterized as "oak-chestnut", but by 1930 most of these trees had been infected by chestnut blight . The root system of blight-killed trees still produces sprouts but they do not get much larger than an inch in diameter before succumbing to

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5518-587: The host rock. For example, a shell consisting of calcite can dissolve while a cement of silica then fills the cavity. In the same way, precipitating minerals can fill cavities formerly occupied by blood vessels , vascular tissue or other soft tissues. This preserves the form of the organism but changes the chemical composition, a process called permineralization . The most common minerals involved in permineralization are various forms of amorphous silica ( chalcedony , flint , chert ), carbonates (especially calcite), and pyrite . At high pressure and temperature,

5607-489: The lake. The turnpike continued past the lake, along present VA 613 , on the western side of Salt Pond Mountain , crossed Potts Mountain dropping down into the Big Stony Creek watershed, continued to cross over Peters Mountain , passed by Salt Sulphur Springs, West Virginia and finally ended at Union, West Virginia. From there stage coaches took travelers to various springs in the area. Route 700 still serves as

5696-522: The land managed by the Mountain Lake Conservancy. A map of trails and a $ 5 annual permit can be obtained at the Mountain Lake Lodge. Other roads and trails in the area are shown on National Geographic Trail Map 788. The area contains forested ridges, dominated by oaks and other hardwoods, and cove forests on sheltered slopes, hollows and along stream valleys. These forests provide good habitat for salamanders. The Appalachian Mountains are

5785-545: The land weaving their clothes and using wooden plowshares for crops. Salt and iron could not be had in the backwoods, so families gathered furs and ginseng to carry by horse to town to exchange for salt and iron. At the close of the Indian Wars in 1794, the country filled rapidly. People built houses, opened farms and roads, elected officers and conducted a civil government without fear of Indian raids. Settlers continued to engage in small scale agriculture until 1892 when

5874-450: The large fluctuations in lake level. Historically the lake has filled and emptied to as low as 20% of its full size. A second study in 1930 observed that the lake is fed mainly by springs rather than surface input. Later studies surmised that the fluctuations in level were due to a competition between leakage and drought. The low 5:1 watershed-area-to-lake-area would create low inflow compared to outflow in dry spells. Millions of years ago,

5963-650: The largest amount of wilderness land is administered by the National Park Service. The largest contiguous wilderness complex in the United States is the Noatak and Gates of the Arctic Wildernesses in Alaska at 12,743,329 acres (5,157,042 ha). The largest wilderness area outside Alaska is the Death Valley Wilderness in southeastern California. The smallest area protected by the WPS is

6052-438: The law prohibits logging , mining , motorized or mechanized vehicles (including bicycles ), road-building, and other forms of development in wilderness areas, though pre-existing mining claims and grazing ranges are permitted through grandfather clauses in the Wilderness Act. Wilderness areas fall into IUCN protected area management category Ia (strict nature preserves) or Ib (wilderness areas). A special exemption to

6141-572: The list changes dramatically, as Alaska contains many of the largest areas protected under the act. In terms of total acres, Alaska , California , Arizona , Idaho , and Washington are the top five states for wilderness, containing almost 80 percent of the acreage in the system. Wilderness totals in most eastern states are modest, with the exceptions of Florida and Minnesota . Wilderness areas exist in every state except Connecticut , Delaware , Iowa , Kansas , Maryland , and Rhode Island . Most U.S. wilderness areas are in national forests, but

6230-435: The lithologies dehydrates. Clay can be easily compressed as a result of dehydration, while sand retains the same volume and becomes relatively less dense. On the other hand, when the pore fluid pressure in a sand layer surpasses a critical point, the sand can break through overlying clay layers and flow through, forming discordant bodies of sedimentary rock called sedimentary dykes . The same process can form mud volcanoes on

6319-450: The mineral dissolved from strained contact points is redeposited in the unstrained pore spaces. This further reduces porosity and makes the rock more compact and competent . Unroofing of buried sedimentary rock is accompanied by telogenesis , the third and final stage of diagenesis. As erosion reduces the depth of burial, renewed exposure to meteoric water produces additional changes to the sedimentary rock, such as leaching of some of

6408-477: The mountains. Mountain Lake has been referred to as "The Silver Gem of the Alleghenies". Many modes of formation have been suggested for the lake. Among the possibilities are the blocking of a stream by talus or slide-rock, a glacial cirque, a depression formed volcanic activity or the result of a meteoric impact. Recent studies have shown that a stream flowing from the Mountain Lake basin was blocked creating

6497-438: The place of deposition. The nature of a sedimentary rock, therefore, not only depends on the sediment supply, but also on the sedimentary depositional environment in which it formed. As sediments accumulate in a depositional environment, older sediments are buried by younger sediments, and they undergo diagenesis. Diagenesis includes all the chemical, physical, and biological changes, exclusive of surface weathering, undergone by

6586-627: The processes responsible for their formation: clastic sedimentary rocks, biochemical (biogenic) sedimentary rocks, chemical sedimentary rocks, and a fourth category for "other" sedimentary rocks formed by impacts, volcanism , and other minor processes. Clastic sedimentary rocks are composed of rock fragments ( clasts ) that have been cemented together. The clasts are commonly individual grains of quartz , feldspar , clay minerals , or mica . However, any type of mineral may be present. Clasts may also be lithic fragments composed of more than one mineral. Clastic sedimentary rocks are subdivided according to

6675-480: The result of localized precipitation due to small differences in composition or porosity of the host rock, such as around fossils, inside burrows or around plant roots. In carbonate rocks such as limestone or chalk , chert or flint concretions are common, while terrestrial sandstones sometimes contain iron concretions. Calcite concretions in clay containing angular cavities or cracks are called septarian concretions . After deposition, physical processes can deform

6764-454: The rock a grey or greenish colour. Iron(III) oxide (Fe 2 O 3 ) in a richer oxygen environment is often found in the form of the mineral hematite and gives the rock a reddish to brownish colour. In arid continental climates rocks are in direct contact with the atmosphere, and oxidation is an important process, giving the rock a red or orange colour. Thick sequences of red sedimentary rocks formed in arid climates are called red beds . However,

6853-480: The rule against mechanized equipment is made for wilderness areas in Alaska : limited use of motorized vehicles and construction of cabins and aquaculture are permitted. These exemptions were allowed due to the large amount of wilderness in Alaska and the concerns of subsistence users, including Alaska Natives . Wilderness areas are parts of national parks , wildlife refuges , national forests , and BLM lands; some units are managed by different agencies. Initially,

6942-469: The same size, the rock is called 'well-sorted', and when there is a large spread in grain size, the rock is called 'poorly sorted'. The form of the clasts can reflect the origin of the rock. For example, coquina , a rock composed of clasts of broken shells, can only form in energetic water. The form of a clast can be described by using four parameters: Chemical sedimentary rocks have a non-clastic texture, consisting entirely of crystals. To describe such

7031-433: The sediment supply, caused, for example, by seasonal changes in rainfall, temperature or biochemical activity. Laminae that represent seasonal changes (similar to tree rings ) are called varves . Any sedimentary rock composed of millimeter or finer scale layers can be named with the general term laminite . When sedimentary rocks have no lamination at all, their structural character is called massive bedding. Graded bedding

7120-402: The sediment, producing a third class of secondary structures. Density contrasts between different sedimentary layers, such as between sand and clay, can result in flame structures or load casts , formed by inverted diapirism . While the clastic bed is still fluid, diapirism can cause a denser upper layer to sink into a lower layer. Sometimes, density contrasts occur or are enhanced when one of

7209-443: The sediment. They can be indicators of circumstances after deposition. Some can be used as way up criteria . Organic materials in a sediment can leave more traces than just fossils. Preserved tracks and burrows are examples of trace fossils (also called ichnofossils). Such traces are relatively rare. Most trace fossils are burrows of molluscs or arthropods . This burrowing is called bioturbation by sedimentologists. It can be

7298-453: The subsurface that is useful for civil engineering , for example in the construction of roads , houses , tunnels , canals or other structures. Sedimentary rocks are also important sources of natural resources including coal , fossil fuels , drinking water and ores . The study of the sequence of sedimentary rock strata is the main source for an understanding of the Earth's history , including palaeogeography , paleoclimatology and

7387-527: The three major types of rock, fossils are most commonly found in sedimentary rock. Unlike most igneous and metamorphic rocks, sedimentary rocks form at temperatures and pressures that do not destroy fossil remnants. Often these fossils may only be visible under magnification . Dead organisms in nature are usually quickly removed by scavengers , bacteria , rotting and erosion, but under exceptional circumstances, these natural processes are unable to take place, leading to fossilisation. The chance of fossilisation

7476-571: The wilderness system in 1980 was due in large part to the Alaska National Interest Lands Conservation Act , signed into law by President Jimmy Carter on December 2, 1980. A smaller spike in 1984 came with the passage of many bills establishing national forest wilderness areas identified by the Forest Service's Roadless Area Review and Evaluation (RARE) process. The Bureau of Land Management

7565-404: The woody tissue of plants. Soft tissue has a much smaller chance of being fossilized, and the preservation of soft tissue of animals older than 40 million years is very rare. Imprints of organisms made while they were still alive are called trace fossils , examples of which are burrows , footprints , etc. As a part of a sedimentary rock, fossils undergo the same diagenetic processes as does

7654-524: The year. This vast assortment of flora and fauna is a major consideration for addition into the wilderness preservation system. Thousands of laws and policies have helped shape and manage the National Wilderness Preservation System in the United States. The following Acts of Congress either directly affect the wilderness system or help influence wilderness management: Some state and tribal governments also designate wilderness areas under their own authority and local laws. These are not federal areas, and

7743-474: Was formed by bodies and parts (mainly shells) of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies ( marine snow ). Sedimentation may also occur as dissolved minerals precipitate from water solution . The sedimentary rock cover of the continents of the Earth's crust is extensive (73% of the Earth's current land surface), but sedimentary rock

7832-403: Was formed to gain insight on the benefits of wilderness preservation, establish open channels of communication between international agencies, and examine the cultural differences and similarities behind preservation efforts in each country. Within the U.S. system, all of the agencies responsible for wilderness preservation will work in cooperation with their international counterparts to determine

7921-687: Was not required to review its lands for inclusion in the NWPS until after October 21, 1976, when the Federal Land Policy and Management Act of 1976 was signed into law; designation of wilderness areas on BLM lands began in 1978. Over 200 wilderness areas have been created within Bureau of Land Management administered lands since then, consisting of approximately 8.71 million acres (3,520,000 ha) in September 2015. As of August 2008, 704 separate wilderness areas, encompassing 107,514,938 acres (43,509,752 ha), had become part of

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