A mountain range or hill range is a series of mountains or hills ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form and alignment that have arisen from the same cause an orogeny. Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics. Mountain ranges are found on many planetary mass objects in the Solar System and are a feature of most terrestrial planets. Mountain ranges are segmented by highlands or mountain passes and valleys. Individual mountains within the same mountain range do not have the same geologic structure or petrology, they may be a mix of different orogenic expressions and terranes, for example thrust sheets, uplifted blocks, fold mountains, volcanic landforms resulting in a variety of rock types. Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or the Alpide Belt.
The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera along the Pacific Coast, the Aleutian Range, on through Kamchatka, Taiwan, the Philippines, Papua New Guinea, to New Zealand. The Andes is 7,000 kilometres long and is considered the world's longest mountain system; the Alpide belt includes Indonesia and Southeast Asia, through the Himalaya, Caucasus Mountains, Balkan Mountains fold mountain range, the Alps, ends in the Spanish mountains and the Atlas Mountains. The belt includes other European and Asian mountain ranges; the Himalayas contain the highest mountains in the world, including Mount Everest, 8,848 metres high and traverses the border between China and Nepal. Mountain ranges outside these two systems include the Arctic Cordillera, the Urals, the Appalachians, the Scandinavian Mountains, the Great Dividing Range, the Altai Mountains and the Hijaz Mountains. If the definition of a mountain range is stretched to include underwater mountains the Ocean Ridges form the longest continuous mountain system on Earth, with a length of 65,000 kilometres.
The mountain systems of the earth are characterized by a tree structure, where mountain ranges can contain sub-ranges. The sub-range relationship is expressed as a parent-child relationship. For example, the White Mountains of New Hampshire and the Blue Ridge Mountains are sub-ranges of the Appalachian Mountains. Equivalently, the Appalachians are the parent of the White Mountains and Blue Ridge Mountains, the White Mountains and the Blue Ridge Mountains are children of the Appalachians; the parent-child expression extends to the sub-ranges themselves: the Sandwich Range and the Presidential Range are children of the White Mountains, while the Presidential Range is parent to the Northern Presidential Range and Southern Presidential Range. The position of mountains influences climate, such as snow; when air masses move up and over mountains, the air cools producing orographic precipitation. As the air descends on the leeward side, it warms again and is drier, having been stripped of much of its moisture.
A rain shadow will affect the leeward side of a range. Mountain ranges are subjected to erosional forces which work to tear them down; the basins adjacent to an eroding mountain range are filled with sediments which are buried and turned into sedimentary rock. Erosion is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains; the early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet of Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to the east; this mass of rock was removed as the range was undergoing uplift. The removal of such a mass from the core of the range most caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment.
Computer simulation has shown that as mountain belts change from tectonically active to inactive, the rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System are isolated and formed by processes such as impacts, though there are examples of mountain ranges somewhat similar to those on Earth. Saturn's moon Titan and Pluto, in particular exhibit large mountain ranges in chains composed of ices rather than rock. Examples include the Mithrim Montes and Doom Mons on Titan, Tenzing Montes and Hillary Montes on Pluto; some terrestrial planets other than Earth exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars, Jupiter's moon Io has mountain ranges formed from tectonic processes including Boösaule Montes, Dorian Montes, Hi'iaka Montes and Euboea Montes. Peakbagger Ranges Home Page Bivouac.com
The Geysers is the world's largest geothermal field, containing a complex of 22 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains 72 miles north of San Francisco, California. For about 12,000 years, Native American tribes built steambaths at the Geysers and used the steam and hot water for healing purposes and cooking; when European Americans first entered the area, six Indian tribes inhabited the area around the Geysers, three bands of Pomo people, two bands of Wappo people, the Lake Miwok people. The Wappo collected sulfur which they called te'ke and a Wappo village, named tekena'ntsonoma was located about 12 miles southeast of Cloverdale and on the present-day Sulphur Creek; the Geysers were first seen by European Americans and named in 1847 during John Fremont's survey of the Sierra Mountains and the Great Basin by William Bell Elliot who called the area "The Geysers," although the geothermal features he discovered were not technically geysers, but fumaroles.
Between 1848 and 1854,Archibald C. Godwin developed The Geysers into a spa named The Geysers Resort Hotel, which attracted tourists including Ulysses S. Grant, Theodore Roosevelt and Mark Twain; the resort declined in popularity in the mid 1880s, rebranded itself to appeal to lower-income people. In 1938, the main building was destroyed in a landslide although the bar/restaurant, small cabins and the swimming pool stayed open, despite another fire in March 1957, until about 1979. Unocal Corporation dismantled the remains of the resort in 1980. Five of the Geysers facilities were damaged in the Valley Fire of September 2015, suffering "severe" damage to their cooling towers; the main power houses were not damaged. The Geysers is the world's largest geothermal field spanning an area of around 30 square miles in Sonoma and Mendocino counties in California, centered in the area of Geyser Canyon and Cobb Mountain. Power from The Geysers provides electricity to Sonoma, Mendocino and Napa counties, it is estimated that the development meets 60% of the power demand for the coastal region between the Golden Gate Bridge and the Oregon state line.
Unlike most geothermal resources, the Geysers is a dry steam field which produces superheated steam. Steam used at The Geysers is produced from a greywacke sandstone reservoir, capped by a heterogeneous mix of low permeability rocks and underlaid by a silicic intrusion. Gravity and seismic studies suggest that the source of heat for the steam reservoir is a large magma chamber over 4 miles beneath the surface, greater than 8 miles in diameter; the first geothermal wells drilled in Geyser Canyon were the first in the Western Hemisphere. The first power plant at the Geysers was developed by the owner of The Geysers Resort and opened in 1921, producing 250 kilowatts of energy to light the resort. In 1960, Pacific Gas and Electric began operation of their 11-megawatt plant at the Geysers; the original turbine produced 11 MW net power. By 1999 the steam to power extraction had begun to deplete the Geysers steam field and production began to drop. However, since October 16, 1997, the Geysers steam field has been recharged by injection of treated sewage effluent, producing 77 megawatts of capacity in 2004.
The effluent is piped up to 50 miles from its source at the Lake County Sanitation waste water treatment plants and added to the Geysers steam field via geothermal injection. In 2003, the City of Santa Rosa and Calpine Corporation partnered on constructing a 42-mile pipeline that became known at the Santa Rosa Geysers Recharge Project. Since 2003, SRGRP has delivered 11 million gallons per day of tertiary treated wastewater to replenish The Geysers’ geothermal reservoir. In 2004, 85% of the effluent produced by four waste-water treatment plants serving 10 Lake County communities was diverted to the Geysers steam field. Injecting treated water into the Geysers field increases the amount of power; the injection of wastewater to the Geysers protects local waterways and Clear Lake by diverting effluent which used to be put into surface waters, has produced electricity without releasing greenhouse gases into the atmosphere. According to the Lawrence Berkeley National Laboratory Earth Sciences division, seismicity was low prior to the use of the Geyser steam field for geothermal energy, although this may have been the result of low seismic coverage of the area.
Before 1969, there were no earthquakes above magnitude 2 recorded by the United States Geological Survey in an 70 square miles area around the Geysers. Studies have shown that injecting water into the Geysers field produces earthquakes from magnitude 0.5 to 3.0, although a 4.6 occurred in 1973 and magnitude four events increased thereafter. With increasing injection rates over time, the rate of magnitude 3 earthquakes has remained unchanged since the 1980s, although the absolute number of earthquakes has increased significantly. A magnitude 4.5 earthquake struck near the Geysers on January 12, 2014 and a magnitude 5.0 on December 14, 2016. Despite the increases in the number of earthquakes and the fears of local residents, it is unlikely that a large earthquake will occur at the Geysers since there is no fault or fracture nearby. In 2005, abatement equipment was installed at two of the Geysers plants to reduce the amount of mercury released by the waste vapor though the amount released was below the legal limit for such releases.
The Geysers Air Monitoring Programs has shown limited releases of arsenic, but again below a significant level. Power plants at the G
Mount Saint Helena
Mount Saint Helena is a peak in the Mayacamas Mountains with flanks in Napa and Lake counties of California. Composed of uplifted 2.4-million-year-old volcanic rocks from the Clear Lake Volcanic Field, it is one of the few mountains in the San Francisco Bay Area to receive any snowfall during the winter. The mountain has five peaks, arranged in a rough "M" shape, its highest point, North Peak, is in Sonoma County. The second-tallest east of the main summit, is the highest point in Napa County; the headwaters of the Napa River are on the southeast slope of Mount Saint Helena. Mount Saint Helena has had an explosive history of pyroclastic flows that resulted in California's Petrified Forest. Mount Saint Helena was named Mount Mayacamas, but the name was changed after a Russian survey party ascended the peak in 1841 and left a copper plate on the summit inscribed with the date of their visit; the plate bore the name of Princess Helena de Gagarin, wife of Alexander G. Rotchev, the commanding officer of Fort Ross.
Robert Louis Stevenson and Fanny Vandegrift Osbourne spent the summer of 1880 honeymooning in an abandoned mining camp on Mount Saint Helena. Stevenson's book The Silverado Squatters includes his experiences while living there; the mount is described by Ambrose Bierce in his ghost story The Death of Halpin Frayser. The peak is reachable by hiking trails leading from Robert Louis Stevenson State Park; the trails are 6 miles long. List of summits of the San Francisco Bay Area "Mount Saint Helena". SummitPost.org. Retrieved 2011-05-07
Clear Lake (California)
Clear Lake is a natural freshwater lake in Lake County in the U. S. state of California, north of Napa County and San Francisco. It is the largest natural freshwater lake wholly within the state, with 68 square miles of surface area. At 480,000 years, it is the oldest lake in North America, it is the latest lake to occupy a site with a history of lakes stretching back at least 2,500,000 years. Known as the "Bass Capital of the West," Clear Lake supports large populations of bass, bluegill and catfish. Two-thirds of the fish caught in Clear Lake are largemouth bass, with a record of 17.52 pounds. Clear Lake was most ranked by Bassmaster Magazine in 2016 as the #3 best bass lake in the United States and the #1 best bass lake on the West Coast. In addition to fish, there is abundant wildlife within the Clear Lake basin. There are year-round populations of ducks, grebes, blue herons, egrets and bald eagles, the basin supports sizable populations of deer, mountain lion and other animals; the expansive, warm water of Clear Lake makes it popular for watersports, such as swimming, water skiing, sailing, boat races, jet skiing.
The California Office of Environmental Health Hazard Assessment has issued a safe advisory for any fish caught in Clear Lake due to elevated levels of mercury. Clear Lake is 19 mi by 8 mi at its widest point, with a surface area of 43,785 acres and a 1,155,000 acre⋅ft capacity. Average depth is 27 ft, maximum is 60 ft, lake elevation is 1,329 ft, average water temperature is 40 °F in winter and 76 °F in summer. Clear Lake is believed to be one of the oldest lakes in North America; the lake sits on a huge block of stone which tilts in the northern direction at the same rate as the lake fills in with sediment, thus keeping the water at the same depth. Core samples of the lake's sediments, taken by U. S. Geological Survey geologists in 1973 and 1980, indicate that the lake is at least 480,000 years old; some experts feel that Mono Lake, to the east of the Sierra Nevada in California, is older than Clear Lake. However, the sedimentary history of Clear Lake is unbroken, while Mono Lake's sediments have been disturbed by past eruptions of the Long Valley Caldera and associated volcanoes.
The geology of Clear Lake is chaotic, with numerous small faults being present in the south end of the lake as well as many volcanoes, ranging in age from 10,000 to 2.1 million years, the largest being Mount Konocti, sitting at the middle of the lake's south shore. At one time Clear Lake was bigger than it is now, included the Blue Lakes. Volcanic eruptions and subsequent landslides changed the landscape forever separating Clear Lake from the Blue Lakes and from its former westward drainage into the Russian River. Archaeologists believe that the Clear Lake basin has been occupied by Native Americans for at least 11,000 years. Evidence of this has been found at nearby Borax Lake and on Rattlesnake Island in the lake's south arm. Abundant fish and waterbirds made Clear Lake an oasis in the otherwise harsh conditions of Northern California's mountains; the native Clear Lake Hitch, was once so abundant that millions of hitch clogged the lake's feeder streams in dry months. When the Spanish missionaries came to California, they found that thousands of Native Americans lived in the Clear Lake Basin Pomo and Wappo with some Lake Miwok.
European settlers arrived, starting around 1845. They abused and exploited the native Pomo people. One of the most notorious incidents was the Bloody Island Massacre of spring 1850. A number of Pomo were enslaved and abused by settlers Andrew Kelsey, whose name is attached to the town of Kelseyville today, Charles Stone; the Pomo revolted and killed Kelsey and Stone. A United States Army contingent under Lieutenant Nathaniel Lyon cornered as many as 200 Pomo on an island in Clear Lake, slaughtered most of them—including scores of women and children; the historical marker for Bloody Island is on Highway 20 between Upper Lake and the Robinson Rancheria. The Pomo were forced to live in small "rancherias" set aside by the federal government. For most of the 20th century, the few remaining Pomo people had to live on these tiny reservations in poverty. Today the fastest-growing businesses around Lake County are the casinos presently operated by four Pomo rancherias, with more casinos planned. Clear Lake was used as an outlying seaplane base for Alameda Naval Air Station during World War II and the early years of the cold war.
Flying boats could land on Clear Lake. Exhibits and programs about the region's culture and history are maintained and presented by rangers and docents at Clear Lake State Park and at Anderson Marsh State Historic Park. Lake County has two county museums, the Lake County Museum in Lakeport and the Lower Lake Historical Schoolhouse Museum in Lower Lake. There are numerous state and local historical landmarks identified throughout the county. Within over 100 miles of shoreline, Clear Lake is a popular spot for water sports enthusiasts. Fishing, sailing, wind surfing, waterskiing and riding personal water craft are all popular activities in the summer. There are 11 free boat launch ramps around the lake. Individuals may rent personal water craft from many businesses around the lake. Clear Lake is sometimes called the "Bass Capital of the West." Largemouth bass, which are farmed and planted in the lake by California Department of Fish and Wildlife, catfish, bluegill
Napa County, California
Napa County is a county north of San Pablo Bay in the northern portion of the U. S. state of California. As of the 2010 census, the population was 136,484; the county seat is the City of Napa. Napa County was one of the original counties of California, created in 1850 at the time of statehood. Parts of the county's territory were given to Lake County in 1861. Napa County comprises the Napa, CA Metropolitan Statistical Area, included in the San Jose-San Francisco-Oakland, CA Combined Statistical Area, it is one of four North Bay counties. Napa County, once the producer of many different crops, is known today for its regional wine industry, rising to the first rank of wine regions with France by local wineries Stag's Leap Wine Cellars and Chateau Montelena winning the "Judgment of Paris" in 1976. In prehistoric times, the valley was inhabited by the Patwin Native Americans, with possible habitation by Wappo tribes in the northwestern foothills. Most villages are thought to have been constructed near the floodplains of watercourses that drain the valley.
Their food consisted of wild roots, small animals, earthworms and bread made from crushed California buckeye kernels. In winter they would construct huts made of tree branches. In summer they streams. In winter months, they were half clad in wild animal skins and at other times they wore no clothing; the maximum prehistoric population is thought not to have exceeded 5000 persons. In 1776, a fort was erected by the Spanish Governor, Felipe de Neve a short distance northwest of Napa, on an elevated plateau. Russians from Sonoma County's Fort Ross grazed cattle and sheep in the Napa Valley in the early 19th century and in 1841 a survey party from the fort placed a plaque on the summit of Mount Saint Helena. Francis Castro and Father Jose Altimura were the first Europeans to explore the Napa Valley, in 1823; when the first white settlers arrived in the early 1830s, there were six tribes in the valley speaking different dialects and they were at war with each other. The Mayacomos tribe lived in the area.
The Callajomans were in the area near. Further south, the Kymus dwelt in the middle part of the valley; the Napa and Ulcus tribes occupied part of the area where the City of Napa now exists while the Soscol tribe occupied the portion that now makes up the southern end of the valley. Many of the native peoples died during a smallpox epidemic in 1838. Settlers killed several over claims of cattle theft. During the era between 1836 and 1846, when California was a province of independent Mexico, the following 13 ranchos were granted in Napa County: George C. Yount was an early settler in Napa County and is believed to be the first Anglo-Saxon resident in the county. In 1836 Yount obtained the Mexican grant Rancho Caymus where he built what is said to be the first log house in California. Soon afterward, he built a sawmill and grain mill, was the first person to plant a vineyard in the county. Following Yount's death in 1865 at age 71, the town of Yountville was named in his honor. Following his marriage to General Vallejo’s niece Maria Guadalupe Soberanes, Edward Turner Bale became a citizen of Mexico and was granted Rancho Carne Humana in the northern end of the valley.
Bale completed building the Bale Grist Mill a few miles north of St. Helena in 1846. Colonel Joseph B. Chiles a guide for one of the earliest immigrant trains to California, was granted Rancho Catacula in 1844; the Town of Napa was founded on Rancho Entre Napa by Nathan Coombs in 1847. Following the event of the Mexican–American War, Bear Flag Revolt in 1846 and the Mexican Cession in 1848, settlers were granted deeds from the original ranchos during the 1850s through 1870s. To this day, a number of streets and landmarks around the valley reflect the names of these ranchos and original grantees. Napa County was formed and became one of the original California counties when the state became part of the United States in 1850. Descendants of George Yount and Captain Edward Bale played key roles in the early development of Napa County. Yount's granddaughter Elizabeth Yount married Thomas Rutherford in 1864; the couple received as a wedding gift from George Yount, land in the area of the valley now known as Rutherford.
Rutherford established himself as a serious grower and producer of fine wines in the following years. Bale's oldest daughter Lolita married the seaman Louis Bruck; when Bale died in 1848, Bruck became the executor of the will for the family. He was elected the first mayor of Napa City when incorporated in 1872. Charles Krug, a fellow Prussian compatriot and pioneer viticulturalist at Sonoma, married Lolita's younger sister Caroline with a dowry that included land near the Bale mill. Krug moved north of St. Helena to establish the valley's first commercial winery. John Patchett opened the first commercial winery in the county in 1859; the vineyard and wine cellar were in an area now in the city limits of Napa. After working as a winemaker for Patchett, Charles Krug founded his own winery in St. Helena 1861; the county's population began to grow in the mid century as pioneers and entrepreneurs moved in and set up residence. During this period, settlers raised cattle and farmed grain and fruit crops.
Mineral mining played a role in the economics of the county. In 1858 the great silver rush began in Napa Valley, miners flocked to the eastern hills. While gold was being prospected in other areas of the state in the 1850s, Napa County became a center for silver and quicksilver mining. In the 1860s, mining carried on, on a large scale, with quicksilver mines operating in many areas of Napa County. In 1866 John Lawley established a toll road from Calistoga over Mount Saint Helena to Lake County. Robert Loui
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, the natural hazards that threaten it; the organization has four major science disciplines, concerning biology, geography and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility; the USGS is a bureau of the United States Department of the Interior. The USGS employs 8,670 people and is headquartered in Reston, Virginia; the USGS has major offices near Lakewood, Colorado, at the Denver Federal Center, Menlo Park, California. The current motto of the USGS, in use since August 1997, is "science for a changing world." The agency's previous slogan, adopted on the occasion of its hundredth anniversary, was "Earth Science in the Public Service." Since 2012, the USGS science focus is directed at six topical "Mission Areas", namely Climate and Land Use Change, Core Science Systems, Ecosystems and Minerals and Environmental Health, Natural Hazards, Water.
In December 2012, the USGS split the Energy and Minerals and Environmental Health Mission Area resulting in seven topical Mission Areas, with the two new areas being: Energy and Minerals and Environmental Health. Administratively, it is divided into six Regional Units. Other specific programs include: Earthquake Hazards Program monitors earthquake activity worldwide; the National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location and magnitude of global earthquakes. The USGS runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System; the USGS informs authorities, emergency responders, the media, the public, both domestic and worldwide, about significant earthquakes. It maintains long-term archives of earthquake data for scientific and engineering research, it conducts and supports research on long-term seismic hazards. USGS has released the UCERF California earthquake forecast.
As of 2005, the agency is working to create a National Volcano Early Warning System by improving the instrumentation monitoring the 169 volcanoes in U. S. territory and by establishing methods for measuring the relative threats posed at each site. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time; the USGS collaborates with Canadian and Mexican government scientists, along with the Commission for Environmental Cooperation, to produce the North American Environmental Atlas, used to depict and track environmental issues for a continental perspective. The USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online. National Climate Change and Wildlife Science Center implements partner-driven science to improve understanding of past and present land use change, develops relevant climate and land use forecasts, identifies lands and communities that are most vulnerable to adverse impacts of change from the local to global scale.
Since 1962, the Astrogeology Research Program has been involved in global and planetary exploration and mapping. In collaboration with Stanford University, the USGS operates the USGS-Stanford Ion Microprobe Laboratory, a world-class analytical facility for U--Pb geochronology and trace element analyses of minerals and other earth materials. USGS operates a number of water related programs, notably the National Streamflow Information Program and National Water-Quality Assessment Program. USGS Water data is publicly available from their National Water Information System database; the USGS operates the National Wildlife Health Center, whose mission is "to serve the nation and its natural resources by providing sound science and technical support, to disseminate information to promote science-based decisions affecting wildlife and ecosystem health. The NWHC provides information, technical assistance, research and leadership on national and international wildlife health issues." It is the agency responsible for surveillance of H5N1 avian influenza outbreaks in the United States.
The USGS runs 17 biological research centers in the United States, including the Patuxent Wildlife Research Center. The USGS is investigating collaboration with the social networking site Twitter to allow for more rapid construction of ShakeMaps; the USGS produces several national series of topographic maps which vary in scale and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest and best-known topographic series is the 7.5-minute, 1:24,000 scale, quadrangle, a non-metric scale unique to the United States. Each of these maps covers an area bounded by two lines of latitude and two lines of longitude spaced 7.5 minutes apart. Nearly 57,000 individual maps in this series cover the 48 contiguous states, Hawaii, U. S. territories, areas of Alaska near Anchorage and Prudhoe Bay. The area covered by each map varies with the latitude of its represented location due to convergence of the meridians. At lower latitudes, near 30° north, a 7.5-minute quadrangle contains an area of about 64 square miles.
At 49° north latitude, 49 square miles are contained within a quadrangle of that size. As a unique non-metric map scale, the 1:24,000 scale requires a separate and specialized romer scale for pl
In modern mapping, a topographic map is a type of map characterized by large-scale detail and quantitative representation of relief using contour lines, but using a variety of methods. Traditional definitions require a topographic map to show both man-made features. A topographic survey is published as a map series, made up of two or more map sheets that combine to form the whole map. A contour line is a line connecting places of equal elevation. Natural Resources Canada provides this description of topographic maps:These maps depict in detail ground relief, forest cover, administrative areas, populated areas, transportation routes and facilities, other man-made features. Other authors define topographic maps by contrasting them with another type of map. However, in the vernacular and day to day world, the representation of relief is popularly held to define the genre, such that small-scale maps showing relief are called "topographic"; the study or discipline of topography is a much broader field of study, which takes into account all natural and man-made features of terrain.
Topographic maps are based on topographical surveys. Performed at large scales, these surveys are called topographical in the old sense of topography, showing a variety of elevations and landforms; this is in contrast to older cadastral surveys, which show property and governmental boundaries. The first multi-sheet topographic map series of an entire country, the Carte géométrique de la France, was completed in 1789; the Great Trigonometric Survey of India, started by the East India Company in 1802 taken over by the British Raj after 1857 was notable as a successful effort on a larger scale and for determining heights of Himalayan peaks from viewpoints over one hundred miles distant. Topographic surveys were prepared by the military to assist in planning for battle and for defensive emplacements; as such, elevation information was of vital importance. As they evolved, topographic map series became a national resource in modern nations in planning infrastructure and resource exploitation. In the United States, the national map-making function, shared by both the Army Corps of Engineers and the Department of the Interior migrated to the newly created United States Geological Survey in 1879, where it has remained since.1913 saw the beginning of the International Map of the World initiative, which set out to map all of Earth's significant land areas at a scale of 1:1 million, on about one thousand sheets, each covering four degrees latitude by six or more degrees longitude.
Excluding borders, each sheet was up to 66 cm wide. Although the project foundered, it left an indexing system that remains in use. By the 1980s, centralized printing of standardized topographic maps began to be superseded by databases of coordinates that could be used on computers by moderately skilled end users to view or print maps with arbitrary contents and scale. For example, the Federal government of the United States' TIGER initiative compiled interlinked databases of federal and local political borders and census enumeration areas, of roadways and water features with support for locating street addresses within street segments. TIGER was used in the 1990 and subsequent decennial censuses. Digital elevation models were compiled from topographic maps and stereographic interpretation of aerial photographs and from satellite photography and radar data. Since all these were government projects funded with taxes and not classified for national security reasons, the datasets were in the public domain and usable without fees or licensing.
TIGER and DEM datasets facilitated Geographic information systems and made the Global Positioning System much more useful by providing context around locations given by the technology as coordinates. Initial applications were professionalized forms such as innovative surveying instruments and agency-level GIS systems tended by experts. By the mid-1990s user-friendly resources such as online mapping in two and three dimensions, integration of GPS with mobile phones and automotive navigation systems appeared; as of 2011, the future of standardized, centrally printed topographical maps is left somewhat in doubt. Topographic maps have multiple uses in the present day: any type of geographic planning or large-scale architecture; the various features shown on the map are represented by conventional symbols. For example, colors can be used to indicate a classification of roads; these signs are explained in the margin of the map, or on a separately published characteristic sheet. Topographic maps are commonly called contour maps or topo maps.
In the United States, where the primary national series is organized by a strict 7.5-minute grid, they are called topo quads or quadrangles. Topographic maps conventionally show land contours, by means of contour lines. Contour lines are curves. In other words, every point on the marked line of 100 m elevation is 100 m above mean sea level; these maps show