Taxodium distichum is a deciduous conifer in the family Cupressaceae. It is native to the southeastern United States. Hardy and tough, this tree adapts to swampy, it is noted for the russet-red fall color of its lacy needles. This plant has some cultivated varieties and is used in groupings in public spaces. Common names include bald cypress, swamp cypress, white cypress, tidewater red cypress, gulf cypress and red cypress. Taxodium distichum is a large, slow-growing, long-lived tree, it grows to heights of 35–120 feet and has a trunk diameter of 3–6 feet. The main trunk is surrounded by cypress knees; the bark is grayish brown to reddish brown and fibrous with a stringy texture. The needle-like leaves are 1⁄2 to 3⁄4 inch long and are simple, alternate and linear, with entire margins. In autumn, the leaves turn yellow or copper red; the bald cypress drops its needles each winter and grows a new set in spring. This species is monoecious, with male and female flowers on a single plant forming on slender, tassel-like structures near the edge of branchlets.
The tree flowers in April and the seeds ripen in October. The male and female strobili are produced from buds formed in late autumn, with pollination in early winter, mature in about 12 months. Male cones emerge on panicles. Female cones are round and green while young, they turn hard and brown as the tree matures. They are 2.0 -- 3.5 cm in diameter. They have from 20 to 30 spirally arranged, four-sided scales, each bearing one, two, or three triangular seeds; each cone contains 20 to 40 large seeds. The cones disintegrate at maturity to release the seeds; the seeds are 5–10 mm long, the largest of any species of Cupressaceae, are produced every year, with heavy crops every 3–5 years. The seedlings have three to nine, but six, cotyledons each; the bald cypress grows in full sunlight to partial shade. This species can tolerate dry soil, it is moderately able to grow in aerosols of salt water. The cones are consumed by wildlife; this tree is suitable for cultivation in light and heavy soils. It does well in acid and alkaline soils and can grow in alkaline and saline soils.
It can grow in no shade. It can grow in water, it can tolerate atmospheric pollution. The tallest known specimen, near Williamsburg, Virginia, is 44.11 m tall, the stoutest known, in the Real County near Leaky, has a diameter at breast height of 475 in. The oldest known living specimen, in Bladen County, North Carolina, is over 1,620 years old, rendering it one of the oldest living plants in North America. Although there are specimens estimated to be nearly 2,000 years old at Sky Lake in Humphreys County, Mississippi determining their age is difficult because older trees become hollow; the related Taxodium ascendens is treated by some botanists as a distinct species, while others classify it as a variety of bald cypress, as Taxodium distichum var. imbricatum Croom. It differs in shorter leaves borne on erect shoots, in ecology, being confined to low-nutrient blackwater habitats. A few authors treat Taxodium mucronatum as a variety of bald cypress, as T. distichum var. mexicanum Gordon, thereby considering the genus as comprising only one species.
The native range extends from southeastern New Jersey south to Florida and west to East Texas and southeastern Oklahoma, inland up the Mississippi River. Ancient bald cypress forests, with some trees more than 1,700 years old, once dominated swamps in the Southeast; the range had been believed to extended north only as far as Delaware, but researchers have now found a natural forest on the Cape May Peninsula in southern New Jersey. The species can be found growing outside its natural native range; the largest remaining old-growth stands are at Corkscrew Swamp Sanctuary, near Naples, in the Three Sisters tract along eastern North Carolina's Black River. The Corkscrew trees are around 500 years of age, some exceed 40 m in height; the Black River trees were cored by dendrochronologist David Stahle from the University of Arkansas. He found that some began growing as early as 364 AD; this species is native to humid climates where annual precipitation ranges from about 760 mm or 30 inches in Texas to 1,630 mm or 64 inches along the Gulf Coast.
Although it grows best in warm climates, the natural northern limit of the species is not due to a lack of cold tolerance, but to specific reproductive requirements: further north, regeneration is prevented by ice damage to seedlings. Larger trees are able to tolerate lower humidity. In 2012 scuba divers discovered an underwater cypress forest several miles off the coast of Mobile, Alabama, in 60 feet of water; the forest contains trees that could not be dated with radiocarbon methods, indicating that they are more than 50,000 years old and thus most lived in the early glacial interval of the last ice age. The cypress forest is well preserved, when samples are cut they still smell like fresh cypress. A team, which has not yet published its results in a peer-reviewed journal, is studying the site. One possibility is that hurricane Katrina exposed the grove of bald cypress, protected under ocean floor sediments; the bald cypress is monoecious. Male and female strobili mature in one growing season from buds formed t
A tire or tyre is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface traveled over. Most tires, such as those for automobiles and bicycles, are pneumatically inflated structures, which provide a flexible cushion that absorbs shock as the tire rolls over rough features on the surface. Tires provide a footprint, designed to match the weight of the vehicle with the bearing strength of the surface that it rolls over by providing a bearing pressure that will not deform the surface excessively; the materials of modern pneumatic tires are synthetic rubber, natural rubber and wire, along with carbon black and other chemical compounds. They consist of a body; the tread provides traction. Before rubber was developed, the first versions of tires were bands of metal fitted around wooden wheels to prevent wear and tear. Early rubber tires were solid. Pneumatic tires are used on many types of vehicles, including cars, motorcycles, trucks, heavy equipment, aircraft.
Metal tires are still used on locomotives and railcars, solid rubber tires are still used in various non-automotive applications, such as some casters, carts and wheelbarrows. The word tire is a short form of attire, from the idea; the spelling tyre does not appear until the 1840s when the English began shrink fitting railway car wheels with malleable iron. Traditional publishers continued using tire; the Times newspaper in Britain was still using tire as late as 1905. The spelling tyre began to be used in the 19th century for pneumatic tires in the UK; the 1911 edition of the Encyclopædia Britannica states that "he spelling'tyre' is not now accepted by the best English authorities, is unrecognized in the US", while Fowler's Modern English Usage of 1926 says that "there is nothing to be said for'tyre', etymologically wrong, as well as needlessly divergent from our own older & the present American usage". However, over the course of the 20th century, tyre became established as the standard British spelling.
The earliest tires were bands of leather iron placed on wooden wheels used on carts and wagons. The tire would be heated in a forge fire, placed over the wheel and quenched, causing the metal to contract and fit on the wheel. A skilled worker, known as a wheelwright, carried out this work; the first patent for what appears to be a standard pneumatic tire appeared in 1847 lodged by the Scottish inventor Robert William Thomson. However, this never went into production; the first practical pneumatic tire was made in 1888 on May Street, Belfast, by Scots-born John Boyd Dunlop, owner of one of Ireland's most prosperous veterinary practices. It was an effort to prevent the headaches of his 10-year-old son Johnnie, while riding his tricycle on rough pavements, his doctor, John Sir John Fagan, had prescribed cycling as an exercise for the boy, was a regular visitor. Fagan participated in designing the first pneumatic tires. Cyclist Willie Hume demonstrated the supremacy of Dunlop's tires in 1889, winning the tire's first-ever races in Ireland and England.
In Dunlop's tire patent specification dated 31 October 1888, his interest is only in its use in cycles and light vehicles. In September 1890, he was made aware of an earlier development but the company kept the information to itself. In 1892, Dunlop's patent was declared invalid because of prior art by forgotten fellow Scot Robert William Thomson of London, although Dunlop is credited with "realizing rubber could withstand the wear and tear of being a tire while retaining its resilience". John Boyd Dunlop and Harvey du Cros together worked through the ensuing considerable difficulties, they employed inventor Charles Kingston Welch and acquired other rights and patents which allowed them some limited protection of their Pneumatic Tyre business's position. Pneumatic Tyre would become Dunlop Tyres; the development of this technology hinged on myriad engineering advances, including the vulcanization of natural rubber using sulfur, as well as by the development of the "clincher" rim for holding the tire in place laterally on the wheel rim.
Synthetic rubbers were invented in the laboratories of Bayer in the 1920s. In 1946, Michelin developed the radial tire method of construction. Michelin had bought the bankrupt Citroën automobile company in 1934, so it was able to fit this new technology immediately; because of its superiority in handling and fuel economy, use of this technology spread throughout Europe and Asia. In the U. S. the outdated bias-ply tire construction persisted, with market share of 87% as late as 1967. Delay was caused by tire and automobile manufacturers in America "concerned about transition costs." In 1968, Consumer Reports, an influential American magazine, acknowledged the superiority of radial construction, setting off a rapid decline in Michelin's competitor technology. In the U. S. the radial tire now has a market share of 100% in automobiles. Today, over 1 billion tires are produced annually in over 400 tire factories. There are 2 aspects to. First, tension in the cords pull on the bead uniformly around the wheel, except where it is reduced above the contact patch.
Second, the bead transfers that net force to the rim. Air pressure, via the ply cords, exerts tensile force on the entire bead surrounding th
Interstate 35 is a major Interstate Highway in the central United States. As with most interstates that end in a five, it is a major cross-country, north-south route stretching from Laredo, Texas, at the Mexican-American border to Duluth, Minnesota, at Minnesota Highway 61 and 26th Avenue East; the highway splits into Interstate 35E and Interstate 35W in two separate places, the Dallas–Fort Worth metroplex in Texas and at the Minnesota twin cities of Minneapolis–Saint Paul. At 1,568 mi, Interstate 35 is the ninth-longest Interstate Highway following Interstate 94, it is the third-longest north-south Interstate Highway, following Interstate 75 and Interstate 95. Though the route is considered to be a border to border highway, this highway does not directly connect to either international border. I-35's southern terminus is a traffic signal in Laredo, just short of the Mexican–American border. Travelers going south can take one of two toll bridges across the Rio Grande and the Mexican border, either straight ahead into the Juarez-Lincoln International Bridge, or via Interstate 35 Business through downtown Laredo into the Gateway to the Americas International Bridge.
To the north, I-35 terminates in Duluth, with connections to Canada from the interstate's terminus via Minnesota Highway 61 to Grand Portage, or north to the border at International Falls, Minnesota via U. S. Route 53 in Duluth, but that route is more accessed from the south by Minnesota Highway 33 at Cloquet, Minnesota. In addition to the Dallas-Fort Worth and Minneapolis-Saint Paul areas, the major cities that I-35 connects to include San Antonio. I-35 northbound begins at a traffic-signaled intersection with Business Spur I-35 in Laredo, just north of the Rio Grande and the international border between Mexico and the US, it has a 17-mile concurrency with U. S. Highway 83. Through Webb, La Salle, Frio counties, it has a north-northeastern course, turning more northeastly around Moore, it cuts across the corners of Medina and Atascosa counties before entering Bexar County and San Antonio. I-35 is named the Pan Am Expressway in San Antonio. There, it has brief concurrencies with I-10 and I-410, it serves as the northern terminus of I-37.
I-35 heads northeast out of the city towards Austin. In Austin, I-35 is the Interregional Highway and has a concurrency with US 290 through Downtown Austin. Throughout Austin, elevated express lanes were constructed on either side of the original freeway. Prior to this expansion, this section included an at-grade railroad crossing, unusual for a freeway. From Austin, I-35 goes through Round Rock, Temple and Waco. In Belton, south of Temple, it serves as the current eastern terminus for I-14. In Waco, I-35 is known as the Jack Kultgen Freeway, begins its concurrency with US 77; the campuses of both the University of Texas at Austin and Baylor University are located adjacent to I-35. I-35 heads to Hillsboro, where it splits into I-35W and I-35E and runs through the Dallas–Fort Worth area; the official mile markers, along with the route of US 77, follow I-35E through Dallas—I-35W, 85 miles in length, carries its own mileage from Hillsboro to Denton, as though it were an x35 loop. In Dallas, I-35E is the R.
L. Thornton Freeway south of I-30, which picks up the name heading east. North of I-30, it is the Stemmons Freeway. After passing through Dallas and Fort Worth, I-35's two forks branches in Denton near the University of North Texas campus; the unified Interstate continues north to Gainesville before crossing the Red River into Oklahoma. In Oklahoma, I-35 runs from the Red River at the Texas border to the Kansas state line near Braman, it passes adjacent to many of the state's major cities. From south to north these cities include Ardmore, Pauls Valley, Norman, Oklahoma City, Del City, Midwest City, Edmond, El Reno, Guthrie and Ponca City. In Downtown Oklahoma City, I-35 has a major junction with I-40 and spurs into I-235 through the north central inner city as heavy traffic follows through the city into the northern area of the state. Between the Oklahoma state line and Emporia, I-35 is part of the Kansas Turnpike; this section of interstate passes through the Flint Hills area. At Emporia, I-35 branches off on its own alignment.
This free section of I-35 provides access to Ottawa before entering the Kansas City Metropolitan Area, where it serves Johnson County, Kansas City, Kansas. Of note on the route, at several points between Cassoday and Emporia in the Flint Hills dirt driveways that provide direct access without a ramp, for cattle trucks, may be found in either direction along the highway. BETO Junction is a highway intersection in Coffey County, Kansas, the intersection of U. S. Highway 75 and I-35, it derives its name from the four major cities nearest the intersection: Burlington, Emporia and Ottawa. It is located 16 miles north of Burlington at exit 155; the intersection referred to as "BETO Junction" before I-35 was constructed was located on the old US 75 highway alignments 2 miles south and 2 miles east, near Waverly, Kansas. I-35 enters Missouri two miles southwest of Kansas City's Central Business District as a six-lane highway. After merging with Southwest Trafficway and Broadway, it becomes eight lanes and continues north to downtown Kansas City, where it serves as the west and north legs of the downtown freeway loop.
Along the north edge of the loop, I-35 joins with I-70 west of Broadway and carries six lanes of traffic with a s
Gonzales is a city in Gonzales County, United States. The population was 7,237 at the 2010 census, it is the county seat. Gonzales is one of the earliest Anglo-American settlements in Texas, the first west of the Colorado River, it was established by Empresario Green DeWitt as the capital of his colony in August 1825. DeWitt named the community for Rafael Gonzáles, governor of Coahuila y Tejas. Informally, the community was known as the DeWitt Colony; the original settlement was abandoned in 1826 after two Indian attacks. It was rebuilt nearby in 1827; the town remains today as it was surveyed. Gonzales is referred to as the "Lexington of Texas" because it was the site of the first skirmish of the Texas Revolution. In 1831, the Mexican government had granted Green DeWitt's request for a small cannon for protection against Indian attacks. At the outbreak of disputes between the Anglo settlers and the Mexican authorities in 1835, a contingent of more than 100 Mexican soldiers was sent from San Antonio to retrieve the cannon.
When the soldiers arrived, there were only 18 men in Gonzales, but they refused to return the cannon, soon men from the surrounding area joined them. Texians under the command of John Henry Moore confronted them. Sarah DeWitt and her daughter sewed a flag bearing the likeness of the cannon and the words "Come and Take It", flown when the first shots of Texan independence were fired on October 2, 1835; the Texians resisted the Mexican troops in what became known as the Battle of Gonzales. Gonzales contributed 32 men from the Gonzales Ranging Company to the defense of the Alamo, it was the only city to send aid to the Alamo, all 32 men lost their lives defending the site. It was to Gonzales that Susanna Dickinson, widow of one of the Alamo defenders, Joe, the slave of William B. Travis, fled with news of the Alamo massacre. General Sam Houston was there organizing the Texas forces, he anticipated the town would be the next target of General Antonio López de Santa Anna's Mexican army. Gathering the Texians at Peach Creek east of town, under the Sam Houston Oak, Houston ordered Gonzales burned, to deny it to the enemy.
He began a retreat toward the U. S. border. The widows and orphans of Gonzales and their neighbors were forced to flee, thus precipitating the Runaway Scrape; the town was derelict after the Texas Revolution, but was rebuilt on the original site in the early 1840s. By 1850, the town had a population of 300; the population rose to 1,703 by time of the 1860 census, 2,900 by the mid-1880s, 4,297 in 1900. Part of the growth of the late 19th century can be attributed to the arrival of various immigrants, among them Jews, many of whom became peddlers and merchants. Gonzales is located in central Gonzales County at 29°30′32″N 97°26′52″W, on the northeast side of the Guadalupe River, just east of the mouth of the San Marcos River. U. S. Route 183 passes through the west side of the city, leading south 32 miles to Cuero and northwest 18 miles to Luling. U. S. Route 90 Alternate passes through the northern side of the city, leading east 18 miles to Shiner and west 33 miles to Seguin. San Antonio is 69 miles to the west, Houston is 136 miles to the east.
According to the United States Census Bureau, Gonzales has a total area of 6.1 square miles, all of it land. As of the census of 2010, there were 2,243 households in the city; the population density was 1,412.8 people per square mile. There were 2,869 housing units at an average density of 562.8 per square mile. The racial makeup of the city was 71.5% White, 7.40% African American, 1.00% Native American, 0.40% Asian, 0.00% Pacific Islander, 21.15% from other races, 2.20% from two or more races. Hispanic or Latino of any race were 47.2% of the population. There were 2,571 households out of which 36.0% had children under the age of 18 living with them, 47.0% were married couples living together, 15.7% had a female householder with no husband present, 31.4% were non-families. 28.2% of all households were made up of individuals and 16.5% had someone living alone, 65 years of age or older. The average household size was 2.73 and the average family size was 3.35. In the city, the population was spread out with 29.7% under the age of 18, 9.6% from 18 to 24, 24.9% from 25 to 44, 18.7% from 45 to 64, 17.0% who were 65 years of age or older.
The median age was 34 years. For every 100 females, there were 91.4 males. For every 100 females age 18 and over, there were 86.5 males. The median income for a household in the city was $27,226, the median income for a family was $34,663. Males had a median income of $22,804 versus $18,217 for females; the per capita income for the city was $12,866. About 14.8% of families and 20.9% of the population were below the poverty line, including 25.5% of those under age 18 and 23.0% of those age 65 or over. During the 19th century, the town was a center for higher education in Texas. Construction began in 1851 and the college opened in 1853, with 50 students. An 1855 addition for the men's program was torn down during the Civil War. By 1857, the school granted bachelor of arts degrees to females, making it one of the earliest colleges in Texas to do so; the college was purchased in 1891, its building converted into a private residence by W. M. Atkinson; the city of Gonzales is served by the Gonzales Independent School District and is home to the Gonzales High School Apaches.
According to the University Interscholastic League of Texas, the Gonzales Apaches football team is in the 4A-1 Region IV District 15. The city of Gonzales a
Texas Hill Country
The Texas Hill Country is a geographic region located in the Edwards Plateau at the crossroads of West Texas, Central Texas, South Texas. Given its location, climate and vegetation, the Hill Country can be considered the border between the American Southwest and Southeast; the region is notable for tall rugged hills of limestone or granite. Many of the hills rise to a height of 400-500 feet above the surrounding plains and valleys, with Packsaddle Mountain rising to a height of 800 feet above the Llano River in Kingsland; the Hill Country includes the Llano Uplift and the second-largest granite dome in the United States, Enchanted Rock. The terrain throughout the region is punctuated by a thin layer of topsoil and a large number of exposed rocks and boulders, making the region dry and prone to flash flooding. Native vegetation in the region includes various yucca, prickly pear cactus, desert spoon, wildflowers in the Llano Uplift; the predominant trees in the region are Texas live oak. Bound on the east by the Balcones Escarpment, the Hill Country reaches into the far northern portions of San Antonio and the western portions of Austin.
As a result of springs discharging water stored in the Edwards Aquifer, several cities such as Austin, San Marcos, New Braunfels were settled at the base of the Balcones Escarpment. The region's economy is one of the fastest growing in the United States. According to the Texas Parks and Wildlife Department, the following 25 counties are included in the Hill Country Wildlife District: During the American Civil War, due to its large, pro-Union, German immigrant population, the Texas Hill Country was opposed to Texas seceding from the Union. Subsequently, in the three quarters of a century following Reconstruction, the core of the Hill Country provided the solitary support base for the Republican Party in what became a one-party Democratic state; when there were no Republicans in the Texas Legislature during the 1930s and 1940s, Gillespie and Kendall Counties backed every Republican Presidential nominee barring Herbert Hoover’s failed 1932 re-election campaign, Republicans continued to control local government.
Guadalupe and Comal Counties were less Republican, but still did not vote for Democratic nominees outside the 1912, 1932, 1936 and 1964 landslides. The region was the only one in antebellum slave states to back the insurgent candidacy of Robert La Follette in 1924: in fact Comal was La Follette’s top county in the nation with 73.96 percent of the vote, it and Gillespie were the only counties south of the Mason-Dixon Line to give a plurality to his “Progressive” ticket. Because of its karst topography, the area features a number of caverns, such as Inner Space Caverns, Natural Bridge Caverns, Bracken Cave, Longhorn Cavern State Park, Cascade Caverns, Caverns of Sonora and Cave Without a Name; the deeper caverns of the area form several aquifers which serve as a source of drinking water for the residents of the area. Wonder Cave in San Marcos was formed by an earthquake along the Balcones Fault. Several tributaries of the Colorado River of Texas — including the Llano and Pedernales rivers, which cross the region west to east and join the Colorado as it cuts across the region to the southeast – drain a large portion of the Hill Country.
The Guadalupe, San Antonio, Frio and Nueces rivers originate in the Hill Country. This region is a dividing line for certain species occurrence. For example, the California Fan Palm is the only species of palm tree, native to the continental United States west of the Hill Country's Balcones Fault; the region has hot summers in July and August, the nighttime temperatures remain high, as the elevation is modest despite the hilly terrain. Winter temperatures are sometimes as much as ten degrees cooler than in other parts of Texas to the east; the area is unique for its fusion of Spanish and German influences in food, beer and music that form a distinctively "Texan" culture separate from the state's Southern and Southwestern influences. For example, the accordion was popularized in Tejano music in the 19th century due to cultural exposure to German settlers. Devil's Backbone is an elevated, winding stretch of Route 32 between San Marcos and Wimberley, continuing through Blanco, that has long been the subject of ghost stories.
Folklore about it appeared in a 1996 episode of NBC's Robert Stack anthology series Unsolved Mysteries, featuring apparitional Spanish monks, Comanche as well as Lipan Apache tribes, Confederate soldiers on their horses, a spirit of a wolf. It re-aired when this series was hosted by Dennis Farina; the region has emerged as the center of the Texas wine industry. Three American Viticultural Areas are located in the areas: Texas Hill Country AVA, Fredericksburg in the Texas Hill Country AVA, Bell Mountain AVA; the Hill Country is known for its tourism. In 2008, The New York Times listed the Hill Country in an article about North American vacation destinations. Hill Country has made Texas second to Florida as the most popular retirement destination in the United States; the region has attracted Baby Boomers as they near retirement age. Frederick Day, a demographer with Texas State University, said that the Hill Country life-style reminds one of the small towns of the recent past. "Like old America... cost of living is pretty low.
To people who have spent their work life in Houston or Dallas, the Hill Country is attractive." Adelsverein Balcones Canyonlands National Wildlife Refuge Cherry Springs Dance Hall German Texan List of geographical regions in Texas Mount Bonnell Revolutions of 1848 Enchanted Rock Hill Country from the Handbook of Texas Online Boerne Directory "Heart of The Hill C
A river delta is a landform that forms from deposition of sediment, carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, estuary, reservoir, or another river that cannot carry away the supplied sediment; the size and shape of a delta is controlled by the balance between watershed processes that supply sediment, receiving basin processes that redistribute and export that sediment. The size and location of the receiving basin plays an important role in delta evolution. River deltas are important in human civilization, as they are major agricultural production centers and population centers, they can impact drinking water supply. They are ecologically important, with different species' assemblages depending on their landscape position. River deltas form when a river carrying sediment reaches either a body of water, such as a lake, ocean, or reservoir, another river that cannot remove the sediment enough to stop delta formation, or an inland region where the water spreads out and deposits sediments.
The tidal currents cannot be too strong, as sediment would wash out into the water body faster than the river deposits it. The river must carry enough sediment to layer into deltas over time; the river's velocity decreases causing it to deposit the majority, if not all, of its load. This alluvium builds up to form the river delta; when the flow enters the standing water, it is no longer confined to its channel and expands in width. This flow expansion results in a decrease in the flow velocity, which diminishes the ability of the flow to transport sediment; as a result, sediment drops out of deposits. Over time, this single channel builds a deltaic lobe; as the deltaic lobe advances, the gradient of the river channel becomes lower because the river channel is longer but has the same change in elevation. As the slope of the river channel decreases, it becomes unstable for two reasons. First, gravity makes the water flow in the most direct course down slope. If the river breaches its natural levees, it spills out into a new course with a shorter route to the ocean, thereby obtaining a more stable steeper slope.
Second, as its slope gets lower, the amount of shear stress on the bed decreases, which results in deposition of sediment within the channel and a rise in the channel bed relative to the floodplain. This makes it easier for the river to breach its levees and cut a new channel that enters the body of standing water at a steeper slope; when the channel does this, some of its flow remains in the abandoned channel. When these channel-switching events occur, a mature delta develops a distributary network. Another way these distributary networks form is from deposition of mouth bars; when this mid-channel bar is deposited at the mouth of a river, the flow is routed around it. This results in additional deposition on the upstream end of the mouth-bar, which splits the river into two distributary channels. A good example of the result of this process is the Wax Lake Delta. In both of these cases, depositional processes force redistribution of deposition from areas of high deposition to areas of low deposition.
This results in the smoothing of the planform shape of the delta as the channels move across its surface and deposit sediment. Because the sediment is laid down in this fashion, the shape of these deltas approximates a fan; the more the flow changes course, the shape develops as closer to an ideal fan, because more rapid changes in channel position results in more uniform deposition of sediment on the delta front. The Mississippi and Ural River deltas, with their bird's-feet, are examples of rivers that do not avulse enough to form a symmetrical fan shape. Alluvial fan deltas, as seen by their name and more approximate an ideal fan shape. Most large river deltas discharge to intra-cratonic basins on the trailing edges of passive margins due to the majority of large rivers such as the Mississippi, Amazon, Ganges and Yangtze discharging along passive continental margins; this phenomenon is due to three big factors: topography, basin area, basin elevation. Topography along passive margins tend to be more gradual and widespread over a greater area enabling sediment to pile up and accumulate overtime to form large river deltas.
Topography along active margins tend to be steeper and less widespread, which results in sediments not having the ability to pile up and accumulate due to the sediment traveling into a steep subduction trench rather than a shallow continental shelf. There are many other smaller factors that could explain why the majority of river deltas form along passive margins rather than active margins. Along active margins, orogenic sequences cause tectonic activity to form over-steepened slopes, brecciated rocks, volcanic activity resulting in delta formation to exist closer to the sediment source; when sediment does not travel far from the source, sediments that build up are coarser grained and more loosely consolidated, therefore making delta formation more difficult. Tectonic activity on active margins causes the formation of river deltas to form closer to the sediment source which may affect channel avulsion, delta lobe switching, auto cyclicity. Active margin river deltas tend to be much smaller and less abundant but may transport similar amounts of sediment.
However, the sediment is never piled up in thick sequences due to the sediment traveling and depositing in de