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Mike Rozier

Michael M. Rozier (born March 1, 1961) is an American former football running back who played in the United States Football League (USFL) for two seasons and the National Football League (NFL) for seven seasons from 1985 to 1991. He played college football for the Coffeyville Red Ravens before transferring to the Nebraska Cornhuskers, where he won the Heisman Trophy in 1983. Afterward, he played for the Pittsburgh Maulers and the Jacksonville Bulls of the USFL, then played for the Houston Oilers and the Atlanta Falcons of the NFL. He was inducted into the College Football Hall of Fame in 2006.

Early life
Rozier was born in Camden, New Jersey. He attended Woodrow Wilson High School in Camden, where he was a standout high school football player. Today, the football field bears his name.

College career
Rozier went largely unnoticed by most of the major college programs. His recruitment to Nebraska was a complete accident. Former Nebraska head coach Frank Solich, at the time an assistant to head coach Tom Osborne, had been a keen observer of high school game films. While watching film of Pennsauken's game against nearby Woodrow Wilson High School, one player on the opposing team (Rozier) continually caught Solich's eye.

Rozier spent his freshman season at Coffeyville Junior College in Kansas, in order to get his grades up. In his one season with the Coffeyville Ravens, he led them to a 9–0 season in 1980, gaining 1157 yards with a gaudy 7.4 yards-per-carry average, and scored ten touchdowns.

As a sophomore in 1981, Rozier first dazzled Husker fans with a 93-yard touchdown run against Kansas State. As the season progressed, Rozier began challenging Roger Craig for the starting position, a job he would eventually win in the fall of 1982 prior to his junior year. Rozier's progress was so pronounced that the talented and established Craig moved to fullback.

During his junior season, Rozier broke Bobby Reynolds's long-standing school record for rushing yards in a single season, with 1,689 yards, and led Nebraska to a second consecutive outright Big 8 title and a 12–1 record, losing only in controversial fashion to eventual national champion Penn State. In a performance against Missouri, Rozier came off the bench in the second half to rush for 139 yards on 17 carries to lead Nebraska to a comeback victory despite suffering from a painful hip-pointer injury. Rozier finished the 1982 season a consensus All-American and finished 10th in the Heisman voting.

As a senior, Nebraska's high-octane offense was often unstoppable, averaging 52 points and 401 rushing yards per game. Rozier had a nation's best 2,486 total yards with 2,148 of those coming on the ground and twenty-nine touchdowns scored. His 7.8 yards-per-carry mark on the season stands as the third-highest mark for players with more than 214 carries in a season. Against Kansas, Rozier rushed for 230 yards in the first half and finished with 285 rushing yards total, at that time a school record. Rozier went over 200 yards in each of his last four regular-season games of the 1983 season. His senior season was capped when he was awarded the Heisman Trophy, given to the best individual player in college football and was again an All-American.

His college career would end in disappointment, losing the 1984 Orange Bowl in which Miami defeated Nebraska 31-30 for the national championship. Rozier had 138 yards on 21 carries at halftime against a Miami Hurricanes team with the second-ranked defense in football, but he had to leave in the third quarter following an ankle injury. Rozier finished the game with 147 yards on 26 carries.

Professional career
Rozier was selected by the Pittsburgh Maulers first overall in the 1984 USFL Draft. He played his first two professional seasons in the United States Football League, in 1984, with the Pittsburgh Maulers, and 1985, with the Jacksonville Bulls. In 1985 Rozier played for the Jacksonville Bulls in the spring and the Houston Oilers in the fall.

He was drafted by the Houston Oilers in the 1st round (2nd pick overall) of the 1984 NFL Supplemental Draft of USFL and CFL Players, joining them in the fall of 1985. Rozier played six seasons for the Oilers, amassing a total of 900 carries for 3171 yards, including a 1,002-yard rushing season in 1988. While playing for the Oilers, Rozier was elected to the AFC Pro Bowl squad in both 1987 and 1988.

In 1990, Rozier only played three games for the Oilers, rushing 10 times for a total of 42 yards, before being released after they found no suitable trade partners. He was quickly picked up by the NFC's Atlanta Falcons, where he finished the year with 153 carries for 675 yards. His final season in the NFL came the next year with the Falcons. He completed the 1991 season with 361 yards on 96 carries, announcing his retirement during the off-season.

Rozier finished his career with a total of 1159 carries for 4462 yards, having averaged 3.8 yards per carry, and scoring 30 touchdowns.

As of the end of the 2020 season, Rozier is ranked 172nd on the NFL All-Time Rushing Yards list.

Personal life
Mike has been married to his wife Rochelle, an attorney, since 2005. They reside in the Sicklerville section of Winslow Township, New Jersey and together they have one son, Michael Guy Pacheco Rozier. He has two other children, Amber and JaMichael Rozier, who reside in Houston, Texas.

In 1996, he was shot in his hometown of Camden, New Jersey. The individual convicted of the shooting of former Husker and Heisman Trophy recipient Mike Rozier in Camden, New Jersey, over two decades ago, has now been released from incarceration.

Rozier, along with his wife and three other family members, appeared on the October 22, 2018 episode of Family Feud.

Mike Rozier is renowned as one of the most stylish dressers in the history of the Heisman Trophy.

On April 9, 2024, Rozier was honored in his hometown of Camden, NJ, with a street dedication. Additionally, a sign was erected in the city proclaiming it the home of the renowned former Nebraska, USFL, and NFL running back.

title: Mike Rozier


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Enrico Caterino Davila

Enrico Caterino Davila (30 October 1576 – 26 May 1631) was an Italian historian and diplomat.

Life
Born in Piove di Sacco, near Padua, he was descended from a Spanish noble family and was the youngest son of Antonio Davila, Grand Constable of Cyprus. His name was given in honour of Henry III of France and Catherine de' Medici.

His immediate ancestors had been constables of the Kingdom of Cyprus for the Venetian republic since 1464. In 1570 the island was taken by the Turks; and Antonio Davila, the father of the historian, had to leave for Padua, despoiled of all his possessions. In 1583 Antonio took this son to France, where he became a page in the service of Catherine de' Medici, wife of King Henry II.

In due time he entered the military service and fought through the French civil wars until the peace in 1598. In 1599, he returned to Padua where he stayed until 1606. Subsequently, he travelled to Parma, Rome and Rovigo and finally settled to Tinos (1609–1615) where he held the post of governor. At Tinos he met and married his wife Ursula delli Ascuffi.

Later in his life Enrico was assigned as a governor of the Venetian possessions of Cattaro (1618–1621) and Zara (1623–1628). Also in 1621, he participated in a Venetian diplomatic mission to Florence, under the leadership of Alvise Valaresso.

Enrico Davila was murdered, while on his way to take possession of the government of Cremona for Venice in May 1631, by a ruffian, with whom a dispute arose about relays of horses ordered for his use by the Venetian government. Davila was killed by a pistol bullet; the murderer's aides also killed the family chaplain but the murderer was killed by Enrico's son 'Antonio' and the rest of the attackers were captured and then publicly executed in Verona.

The Istoria
He planned a history of the civil wars in France in which he had taken part, and during which he had seen the leading personages and events. This work was completed about 1630 and was offered by the author to the publishers in Venice. At last Tommaso Baglioni, who had no work for his presses, undertook to print the manuscript, on condition that he should be free to leave off if more promising work offered itself. The printing of the Istoria delle guerre civili di Francia was, however, completed, and the success of the work was immediate.

The Historia delle guerre civili di Francia is based on first-hand knowledge of events and personalities. Sceptical about the religious claims of both sides (Catholic and Huguenot), Davila vividly portrayed the French wars of religion mainly as a struggle between noble factions for the control of the royal government and, within limits, is still a rich source of information for a troubled period of French history.

Over two hundred editions followed, of which perhaps the best is the one published in Paris in 1644. An English translation was made for Charles I of England by William Aylesbury and Charles Cotterell, published as The Historie of the Civil Warres of France (1647). Samuel Pepys was appreciative.

Lord Bolingbroke, in his fifth letter on the Study of History, recommends him very strongly as a writer equal in many respects to Livy. The American statesman and political thinker John Adams wrote his last work of political theory, the Discourses on Davila, as an extended commentary on Davila's history of the French civil wars, following the example of Machiavelli's Discorsi on Livy's history of Rome.

His name is often anglicised as Henry Catherine Davilla.

Works

 * 1) Theatro del Mondo (Unpublished, 1598–1599)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Enrico Caterino Davila


text: User talk:164.92.250.8

title: User talk:164.92.250.8


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Arthur II, Duke of Brittany

Arthur II (25 July 1261 – 27 August 1312), of the House of Dreux, was Duke of Brittany from 1305 to his death. He was the first son of John II and Beatrice, daughter of Henry III of England and Eleanor of Provence.

After he inherited the ducal throne, his brother John became Earl of Richmond.

As duke, Arthur was independent of the French crown. He divided his duchy into eight "battles": Léon, Kernev, Landreger, Penteur, Gwened, Naoned, Roazhon, and Sant Malou. In 1309, he convoked the first Estates of Brittany. It was the first time in French history that the third estate was represented.

Arthur died at Château de l'Isle in Saint Denis en Val and was interred in a marble tomb of the cordeliers of Vannes. The tomb was vandalised during the French Revolution, but later repaired and is on display today.

Marriages and children
In 1275, Arthur married Marie, Viscountess of Limoges, daughter of Guy VI, Viscount of Limoges, and Margaret, Lady of Molinot. Her maternal grandparents were Hugh IV, Duke of Burgundy, and his first wife, Yolande of Dreux. They were parents of three children:

 * John III, Duke of Brittany (8 March 1286 – 30 April 1341).
 * Guy de Penthièvre, Count of Penthièvre (1287 – 1331); father of Joanna of Penthièvre.
 * Peter of Brittany, Seigneur of Dol-Combourg and Sant-Maloù (1289 – 1312).

Marie died in 1291. In May 1292, Arthur married Yolande of Dreux, who was Countess of Montfort, daughter of Robert IV, Count of Dreux, and Beatrice de Montfort. Yolande had briefly been Queen of Scotland by her first marriage. They were parents of six children:

 * John of Montfort (1295 – 16 September 1345).
 * Beatrice of Brittany (1295–1384); married Guy X, Lord of Laval.
 * Joan of Brittany (1296–1364); married Robert, Count of Marle, Lord of Cassel (son of Robert III, Count of Flanders).
 * Alice of Brittany (1297–1377); married Bouchard VI, Count of Vendôme, a member of the House of Montoire.
 * Blanche of Brittany (born c. 1300); considered to have died young.
 * Marie of Brittany (1302–1371); a nun.

title: Arthur II, Duke of Brittany


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Ziph

Ziph or Zif may refer to:

 * Ziph (Bible), a town of the Tribe of Judah, near Hebron
 * Wilderness of Ziph, a desert near the town of Ziph mentioned as the place where David hid himself from
 * Another Judahite town named Ziph, south at the borders of the land of Edom
 * One of five words inscribed on LMLK seals, possibly referring to the Judahite town of Ziph
 * Zif, a Palestinian village close to Hebron, identified with the biblical Ziph

title: Ziph


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Collapse of the World Trade Center

The World Trade Center in New York City collapsed on September 11, 2001, as result of the al-Qaeda attacks. Two commercial airliners hijacked by al-Qaeda terrorists were deliberately flown into the Twin Towers of the complex, resulting in a total progressive collapse that killed almost 3,000 people. It is the deadliest and costliest building collapse in history.

The North Tower (WTC 1) was the first building to be hit when American Airlines Flight 11 crashed into it at 8:46 a.m., causing it to collapse at 10:28 after burning for one hour and 42 minutes. At 9:03 a.m., the South Tower (WTC 2) was struck by United Airlines Flight 175; it collapsed at 9:59 a.m. after burning for 56 minutes.

The towers' destruction caused major devastation throughout Lower Manhattan, and more than a dozen adjacent and nearby structures were damaged or destroyed by debris from the plane impacts or the collapses. Four of the five remaining World Trade Center structures were immediately crushed or damaged beyond repair as the towers fell, while 7 World Trade Center remained standing for another six hours until fires ignited by raining debris from the North Tower brought it down at 5:21 that afternoon.

The hijackings, crashes, fires and subsequent collapses killed an initial total of 2,760 people. Toxic powder from the destroyed high-rises was dispersed throughout the city and gave rise to numerous long-term health effects that continue to plague many who were in the towers' vicinity, with at least three additional deaths reported. The 110-story towers are the tallest freestanding structures ever to be destroyed, and the death toll from the attack on the North Tower represents the deadliest terrorist act in world history.

In 2005, the National Institute of Standards and Technology (NIST) published the results of its investigation into the collapse. It found nothing substandard in the towers' design, noting that the severity of the attacks was beyond anything experienced by buildings in the past. The NIST determined the fires to be the main cause of the collapses, finding that sagging floors pulled inward on the perimeter columns, causing them to bow and then buckle. Once the upper section of the building began to move downward, a total progressive collapse was unavoidable.

The cleanup of the World Trade Center site involved round-the-clock operations and cost hundreds of millions of dollars. Some of the surrounding structures that had not been hit by the planes still sustained significant damage, requiring them to be torn down. Demolition of the surrounding damaged buildings continued even as new construction proceeded on the Twin Towers' replacement, the new One World Trade Center, which opened in 2014.

Background
When they opened in 1973, the Twin Towers were the tallest buildings in the world. At the time of the attacks only the Petronas Towers in Kuala Lumpur, Malaysia and the Willis Tower (known then as the Sears Tower) in Chicago were taller. Built with a novel "framed tube" design that maximized interior space, the towers had a high strength-to-weight ratio requiring 40 percent less steel than more traditional steel framed skyscrapers. In addition, atop WTC 1 stood a 362 foot telecommunications antenna erected in 1978, bringing that tower's total height to 1730 ft, though as a nonstructural addition, the antenna was not officially counted.

Structural design
The towers were designed as framed tube structures, which provided tenants with open floor plans uninterrupted by columns or walls. The buildings were square and 207 ft on each side but had chamfered 6 ft corners, making each building's exterior roughly 210 ft wide. One World Trade Center (WTC 1), the "North Tower", was, at 1368 ft, six feet taller than Two World Trade Center (WTC 2), the "South Tower", which was 1362 ft tall. Numerous closely spaced perimeter columns provided much of the structural strength, along with gravity load shared with the steel box columns of the core. Above the tenth floor, there were 59 perimeter columns along each face of the building spaced 3 ft on center. While the towers were square, the interior cores were rectangular and supported by 47 columns that ran the full height of each tower. All the elevators and stairwells were in the core, leaving a large column-free space between it and the perimeter that was bridged by prefabricated floor trusses. As the core was rectangular, this created a long and short span distance to the perimeter columns.

The floors consisted of 4 in lightweight concrete slabs laid on a fluted steel deck. A grid of lightweight bridging trusses and main trusses supported the floors with shear connections to the concrete slab for composite action. The trusses had a span of 60 ft in the long-span areas and 35 ft in the short-span area. The trusses connected to the perimeter at alternate columns, and were therefore on 6.8 ft centers. The top chords of the trusses were bolted to seats welded to the spandrels on the perimeter side and a channel welded to interior box columns on the core side. The floors were connected to the perimeter spandrel plates with viscoelastic dampers, which helped reduce the amount of sway felt by building occupants. The towers also had a "hat truss" or "outrigger truss" between the 107th and 110th floors, consisting of six trusses along the long axis of core and four along the short axis. This system allowed optimized load redistribution of floor diaphragms between the perimeter and core, with improved performance between the different materials of flexible steel and rigid concrete allowing the moment frames to transfer sway into compression on the core, which also mostly supported the transmission tower. These trusses were installed in each building to support future transmission towers, but only the north tower was ultimately fitted with one.

Evaluations for aircraft impact
Though fire studies and even an analysis of the impacts of low-speed jet aircraft impacts had been undertaken before the towers' completion, the full scope of those studies no longer exists. Nevertheless, since fire had never before caused a skyscraper to collapse and aircraft impacts had been considered in their design, their destruction initially came as a surprise to some in the engineering community.

The structural engineers working on the World Trade Center considered the possibility that aircraft could crash into the building. In July 1945, a B-25 bomber that was lost in fog had crashed into the 79th floor of the Empire State Building. A year later, a C-45F Expeditor crashed into the 40 Wall Street building. Once again, fog was believed to have been the contributing factor in the collision. Leslie Robertson, one of the chief engineers working on the design of the World Trade Center, said that he considered the scenario of the impact of a Boeing 707, which might be lost in the fog and flying at relatively low speeds while seeking to land at either JFK or Newark Airports. In an interview with the BBC two months after the towers collapsed, Robertson said: "with the 707, the fuel load was not considered in the design. I don't know how it could have been considered." He also said that the main difference between the design studies and the event that caused the towers to collapse was the velocity of the impact, which greatly increased the absorbed energy, and was never considered during the construction process.

During its investigation into the collapse, the National Institute of Standards and Technology (NIST) obtained a three-page white paper that stated the buildings would survive an aircraft-impact of a Boeing 707 or DC 8 flying at 600 mph. In 1993, John Skilling, lead structural engineer for the WTC, said in an interview conducted after the 1993 World Trade Center bombing: "Our analysis indicated the biggest problem would be the fact that all the fuel would dump into the building. There would be a horrendous fire. A lot of people would be killed. The building structure would still be there." In its report, NIST stated that the technical ability to perform a rigorous simulation of aircraft impact and ensuing fires is a recent development, and that the technical capability for such analysis would have been quite limited in the 1960s. In its final report on the collapses, the NIST stated that it could find no documentation examining the impact of a high-speed jet or of a large-scale fire fueled by aviation fuel.

Fireproofing
Until the mid-1970s, the use of asbestos for fireproofing was widespread in the construction industry. But in April 1970, the New York City Department of Air Resources ordered contractors building the World Trade Center to stop the spraying of asbestos as an insulating material and vermiculite plaster was used instead.

After the 1993 bombing, inspections found fireproofing to be deficient. Before the collapses, the towers' owner, the Port Authority of New York and New Jersey, was in the process of adding fireproofing, but had completed only 18 floors in WTC 1, including all the floors affected by the aircraft impact and fires, and 13 floors in WTC 2, although none were directly affected by the aircraft impact.

NIST concluded that the aircraft impact sheared off a significant portion of the fireproofing, contributing to the buildings' collapse. In WTC 1, the impact stripped the insulation off most core columns (43 of 47) on more than one floor, as well as floor trusses over a space of 60000 sqft. In WTC 2 the impact knocked off insulation from 39 of the 47 columns on multiple floors, and also from floor trusses spanning an area of 80000 sqft.

After the collapses, Leslie E. Robertson said: "To the best of our knowledge, little was known about the effects of a fire from such an aircraft, and no designs were prepared for that circumstance. Indeed, at that time, no fireproofing systems were available to control the effects of such fires."

Aircraft impacts and resultant fires
During the September 11 attacks, four teams of al-Qaeda terrorists hijacked four different jetliners. Two of these jetliners, American Airlines Flight 11 and United Airlines Flight 175, both Boeing 767s, were hijacked after takeoff from Boston's Logan International Airport. In its final moments, American Airlines Flight 11 flew south over Manhattan and crashed at roughly 440 mph into the northern facade of the North Tower (WTC 1) at 8:46 a.m., hitting the 93rd through 99th floors. Seventeen minutes later, United Airlines Flight 175 flew northeast, over New York Harbor, and crashed into the southern facade of the South Tower (WTC 2) at 9:03 a.m., striking between the 77th through 85th floors at 540 mph.

The impacts failed the exterior columns in the regions hit by the fuselage, engines, and fuel-filled wing section (34 columns in the North Tower and 26 in the South Tower). Damage also extended to the tips of the wings and tailfin. In addition, several core columns were either severed or heavily damaged, especially in the path of the fuselage.

About one third of the fuel was consumed in the initial impact and resulting fireball. Some fuel from the impact traveled down at least one elevator shaft and exploded on the 78th floor of the North Tower, as well as in the main lobby. The towers' light construction and hollowness allowed the jet fuel to penetrate far inside them, igniting many large fires simultaneously over a wide area of the impacted floors. The fuel burned for at most a few minutes, but the buildings' contents burned over the next hour or hour and a half.

As Flight 175 struck the South Tower, the shockwave shattered glass on the east face of the North Tower adjacent to the fireball, which aggravated the fires already burning in the North Tower and released plumes of smoke from the newly opened windows. It is unknown whether Flight 11's impact did the same to windows on the South Tower. In any case, the major debris from Flight 11 flew past the South Tower, while the more significant pieces of wreckage from Flight 175 similarly missed the already burning North Tower. In both instances, some of these parts landed on other nearby buildings, resulting in further destruction.

The fires in each building had different attributes, as was evident in the responses and behavior of people trapped in each. Countless windows in the North Tower were smashed by occupants seeking relief from the hellish conditions inside. While some windows were broken in the South Tower, it was relatively uncommon by comparison. Victims were only occasionally spotted inside open windows, and no crowds were present outside of the tower, as in the Impending Death photograph of the North Tower burning.

Numerous people fell or jumped to their deaths from the burning towers. Three were spotted from an east-facing window on the south side of the 79th floor, while the 100–200 people who fell or jumped from the four faces of the North Tower had no other means of escape from the insufferable heat, smoke and fire consuming its top 18 stories.

Such differences imply that conditions did not deteriorate as rapidly, or become as inhospitable, in the South Tower as in the North. The damage to the North Tower by Flight 11's centered impact severed all escape routes above the 91st floor and left the stranded workers in an insufferable inferno from which jumping was their only means of escape; Flight 175 struck the South Tower through the southeast corner of the skyscraper's southern facade and left the northwesternmost stairwell undamaged from top to bottom. The intact stairway meant people in the South Tower were not completely trapped, which may have influenced their decision to jump.

The fireballs resulting from each impact were likely very similar, but appeared vastly different in size despite the planes carrying similar amounts of combustibles. This is because a substantial portion of the jet fuel was channelled into the North Tower instead of being sprayed out into the open. Flight 11 crashed almost midway into the North Tower's central core, causing the ignited jet fuel to shoot through elevator shafts down as far as the basement and concourse levels, with a flash fire exploding from elevators in the ground floor lobby, more than 90 floors below the impact. Flight 175's impact into the South Tower's south face was offset to the east rather than being centralized like Flight 11, leaving the sides of the tower as the only real direction in which the fuel could travel, producing a visibly larger fireball on the outside.

Emergency response and evacuation
Almost all the deaths in the Twin Towers occurred in the zones above the points of aircraft impact. As the North Tower had been struck almost directly midway into the structure, the three main stairways (A, B, and C) in the tower core were all damaged or blocked by debris preventing escape to lower floors. In the South Tower, the impact was east of center to the central section of the tower and close to the southeast corner, resulting in stairway A in the northwest portion of the central core being intact and only partially blocked, and 18 civilians managed to escape from the point of aircraft impact and the floors above that. The exact numbers of who perished and where in some cases is not precisely known; however the National Institute of Standards and Technology report indicated that a total of 1,402 civilians perished at or above the impact point in the North Tower with hundreds estimated to have been killed at the moment of impact. In the South Tower, 614 civilians perished at the impacted floors and the floors above that. Fewer than 200 of the civilian fatalities occurred in the floors below the impact points but all 147 civilian passengers and crew on the two aircraft as well as all 10 terrorists perished, along with at least 18 people on the ground and in adjacent structures.

All told, emergency personnel killed as a result of the collapse included 342 members of the New York City Fire Department (FDNY), 71 law enforcement officers including 23 members of the New York City Police Department (NYPD), 37 members of the Port Authority Police Department (PAPD), five members of the New York State Office of Tax Enforcement (OTE), three officers of the New York State Office of Court Administration (OCA), one fire marshal of the New York City Fire Department (FDNY) who had sworn law enforcement powers (and was also among the 343 FDNY members killed), one member of the Federal Bureau of Investigation (FBI), and one member of the United States Secret Service (USSS). The total death toll for civilian and non-civilians is estimated to be 2,606 persons.

Collapse of the Towers
The destruction of the Twin Towers has been called "the most infamous paradigm" of progressive collapse. Each collapse began with the local failure of the vertical load-bearing components of the floors that were hit by the planes and progressed to encompass the whole of the structure. Structural components were severed, releasing gravitational energy that transferred loads downwards by way of serially propagating impact forces. Excepting the top floors of the building, which would not have released sufficient gravitational energy to bring about a total collapse, the collapses could have begun with the failure of any story.

The towers collapsed symmetrically and more or less straight down, though there was some tilting of the tops of the towers and a significant amount of fallout to the sides. As the collapse progressed, dust and debris could be seen shooting out of the windows several floors below the advancing destruction, caused by the sudden rush of air compressed under the descending upper levels.

During each collapse, large portions of the perimeter columns and the cores were left without any lateral support, causing them to fall laterally towards the outside, pushed by the increasing pile of rubble. Consequently, the walls peeled off and separated from the buildings by a large distance – about 500 feet in some cases – hitting neighboring buildings and starting fires that would later lead to the collapse of Building 7. Some connections broke as the bolts snapped, leaving many panels randomly scattered. The first fragments of the outer walls of the collapsed North Tower struck the ground 11 seconds after the collapse started, and parts of the South Tower after 9 seconds. The lower portions of both buildings' cores (60 stories of WTC 1 and 40 stories of WTC 2) remained standing for up to 25 seconds after the start of the initial collapse before they too collapsed.

Collapse initiation
In both towers, the section of the building that had been damaged by the airplanes failed. Aside from the structural damage, the impacts had removed fireproofing from a large part of the impact zone allowing the structural steel to heat rapidly. As a result, the core columns were weakened and began to shorten due to creep. The hat truss resisted this by shifting loads to the perimeter columns. Meanwhile, web diagonals of the 60 foot trusses supporting the long-span tenant floor area began to buckle, causing the floors to sag by more than 2 feet. This pulled in the perimeter walls, which buckled. The floors above the impact zone now fell freely onto the undamaged structure below.

The North Tower lasted around 46 minutes longer than its twin, having been struck 17 minutes before the South Tower was attacked and standing another half-hour after the South Tower collapsed. This was because Flight 11 struck more or less in the center, causing more symmetrical impact damage to the North Tower's core and leaving more of its structural support intact. The fires also took more than an hour to spread to the south side of the building, where there was fireproofing damage. Traveling at 440 miles per hour, Flight 11 crashed through Floors 93 and 99, leaving only 10 floors' worth of structural weight pressing down on the damaged, burning section of the North Tower.

Flight 175's much higher impact speed inflicted structural damage even more catastrophic than Flight 11's, which was compounded by the plane slicing through the southeastern corner rather than the center, unbalancing the South Tower on one side. The uneven weight distribution was significantly aggravated by Flight 175 crashing much lower down, between Floors 77 and 85, resulting in more pressure on both the perimeter wall columns and core columns than in the North Tower and causing them to snap more quickly. The difference in the impacts was such that a senior FDNY chief reportedly expressed strong disbelief that the North Tower would collapse even after witnessing the collapse of the South Tower, because the North had not been struck at a corner.

Total progressive collapse
When the columns failed, the entire building above fell onto the first intact floor beneath impact. The vertical capacity of the connections supporting an intact floor below the level of collapse was adequate to carry the load of 11additional floors if the load were applied gradually, but of only 6additional floors if the load were applied suddenly —as was the case. Since the number of floors above the approximate floor of collapse initiation exceeded six in each WTC tower (12 floors in WTC 1 and 29 floors in WTC 2), the floors below the level of collapse initiation were unable to resist the suddenly applied gravitational load from the upper floors of the buildings.

From there collapse proceeded through two phases. During the crush-down phase, the upper block destroyed the structure below in a progressive series of floor failures roughly one story at a time. Each failure began with the impact of the upper block on the floor plate of the lower section, mediated by a growing layer of rubble consisting mainly of concrete from the floor slabs. The energy from each impact was "reintroduced into the structure in [the] subsequent impact, ... concentrate[d] in the load-bearing elements directly affected by the impact." This overloaded the floor connections of the story immediately beneath the advancing destruction, causing them to detach from the perimeter and core columns. The perimeter columns peeled away and the cores were left without lateral support.

This continued until the upper block reached the ground and the crush-up phase began. Here, it was the columns that buckled one story at a time, now starting from the bottom. As each story failed, the remaining block fell through the height of the story, onto the next one, which it also crushed, until the roof finally hit the ground. The process accelerated throughout, and by the end each story was being crushed in less than a tenth of a second.

South Tower collapse

As the fires continued to burn, occupants trapped in the upper floors of the South Tower provided information about conditions to 9-1-1 dispatchers. At 9:37 a.m., an occupant on the 105th floor of the South Tower reported that floors beneath him "in the 90-something floor" had collapsed. The New York City Police Department aviation unit also relayed information about the deteriorating condition of the buildings to police commanders. At 9:51 a.m., seven minutes before the collapse, the NYPD aviation unit reported that large pieces of debris were hanging or falling from the South Tower. The implied threat of an imminent collapse was sufficient for the NYPD to order its officers to evacuate, although none of the helicopter pilots specifically predicted that either tower would fall. During the emergency response, there was little communication between the NYPD and the FDNY, and overwhelmed 9-1-1 dispatchers did not pass along information to FDNY commanders at the scene. At 9:59 a.m.,  the South Tower collapsed, 56 minutes after Flight 175 crashed into it.

Before the South Tower collapsed, 18 people escaped from the impact zone and the floors above, including Stanley Praimnath, who had seen the plane coming at him. They made it out via Stairwell A, the only stairway left intact after the crash. There may have been other previously trapped occupants who were descending from the impact zone when the tower collapsed. Numerous police hotline operators who received calls from people in the South Tower were not well informed of the situation as it rapidly unfolded. Many operators told callers not to descend on their own, even though it is now believed that Stairwell A was probably passable at and above the point of impact.

North Tower collapse
The South Tower's collapse shattered windows and damaged other exterior elements along the North Tower's southern and eastern facades, although this was insufficient to cause its subsequent collapse. After the South Tower fell, NYPD helicopters relayed information about the deteriorating conditions of the North Tower, while FDNY commanders issued orders for firefighters in the North Tower to evacuate. Poor radio reception meant firefighters inside the North Tower did not hear the evacuation order from their supervisors on the scene, and most were unaware that the other tower had collapsed. An NYPD officer said at 10:06 a.m. that the North Tower was not going to last much longer and recommended that emergency vehicles be pulled away from the complex. At 10:20 a.m., the NYPD aviation unit reported that "the top of the tower might be leaning", and a minute later confirmed that the North Tower was buckling on the southwest corner and leaning to the south, prompting an officer to begin urging all NYPD personnel in the building's vicinity to retreat at least three blocks in every direction. The aviation unit declared at 10:27 "the roof is going to come down very shortly"; this proved correct less than a minute later, when the North Tower collapsed at 10:28 a.m., one hour and 42 minutes after being struck.

Because all escape routes from the impact zone, above it, and immediately below it were severed when Flight 11 crashed, no one above the 91st floor survived. The collapsing towers generated enormous clouds of dust and debris, which enveloped lower Manhattan; light dust reached as far as the Empire State Building, 2.93 mi away. The debris cloud from the North Tower collapse was also larger and more widespread than that of the South Tower, because the collapse of the North also kicked up dust from the South Tower.

Building 7 collapse
As the North Tower collapsed, heavy debris hit 7 World Trade Center, causing damage to the south face of the building and starting fires that continued to burn throughout the afternoon. Structural damage occurred to the southwest corner between Floors 7 and 17 and on the south facade between Floor 44 and the roof; other possible structural damage includes a large vertical gash near the center of the south facade between Floors 24 and 41. The building was equipped with a sprinkler system, but had many single-point vulnerabilities for failure: the sprinkler system required manual initiation of the electrical fire pumps, rather than being a fully automatic system; the floor-level controls had a single connection to the sprinkler water riser; and the sprinkler system required some power for the fire pump to deliver water. Also, water pressure was low, with little or no water to feed sprinklers. Some firefighters entered 7 World Trade Center to search the building. They attempted to extinguish small pockets of fire, but low water pressure hindered their efforts. Fires burned into the afternoon on the 11th and 12th floors of 7 World Trade Center, the flames visible on the east side of the building. During the afternoon, fire was also seen on floors 6–10, 13–14, 19–22, and 29–30. In particular, the fires on floors 7 through 9 and 11 through 13 continued to burn out of control during the afternoon. At approximately 2:00 pm, firefighters noticed a bulge in the southwest corner of 7 World Trade Center between the 10th and 13th floors, a sign that the building was unstable and might cave to one side or "collapse". During the afternoon, firefighters also heard creaking sounds coming from the building and issued uncertain reports about damage in the basement. Around 3:30 pm FDNY Chief Daniel A. Nigro decided to halt rescue operations, surface removal, and searches along the surface of the debris near 7 World Trade Center and evacuate the area due to concerns for the safety of personnel. At 5:20:33 pm EDT on September 11, 2001, 7 World Trade Center started to collapse, with the crumble of the east mechanical penthouse, while at 5:21:10 pm EDT the entire building collapsed completely. There were no casualties associated with the collapse. When 7 World Trade Center collapsed, debris caused substantial damage and contamination to the Borough of Manhattan Community College's Fiterman Hall building, located adjacent at 30 West Broadway, to the extent that the building was not salvageable. In August 2007, Fiterman Hall was scheduled for dismantling. A revised plan called for demolition in 2009 and completion of the new Fiterman Hall in 2012, at a cost of $325 million. The building was finally demolished in November 2009 and construction of its replacement began on December 1, 2009. The adjacent Verizon Building, an Art Deco building constructed in 1926, had extensive damage to its east facade from the collapse of 7 World Trade Center, though it was successfully restored at a cost of US$1.4 billion.

Other buildings
Many of the surrounding buildings were also either damaged or destroyed as the towers fell. 5 WTC endured a large fire and a partial collapse of its steel structure and was torn down. Other buildings destroyed include St. Nicholas Greek Orthodox Church, Marriott World Trade Center (Marriott Hotel 3 WTC), South Plaza (4 WTC), and U.S. Customs (6 WTC). The World Financial Center buildings, 90 West Street, and 130 Cedar Street suffered fires. The Deutsche Bank Building, the Verizon Building, and World Financial Center 3 had impact damage from the towers' collapse, as did 90 West Street. One Liberty Plaza survived structurally intact but sustained surface damage including shattered windows. 30 West Broadway was damaged by the collapse of 7 WTC. The Deutsche Bank Building, which was covered in a large black "shroud" after September 11 to cover the building's damage, was deconstructed because of water, mold, and other severe damage caused by the neighboring towers' collapse. In addition to this, many works of art were destroyed in the collapse.

Initial opinions and analysis
In the immediate aftermath of the attacks, numerous structural engineers and experts spoke to the media, describing what they thought caused the towers to collapse. Abolhassan Astaneh-Asl, a structural engineering professor at the University of California at Berkeley, explained that the high temperatures in the fires weakened the steel beams and columns, causing them to become "soft and mushy", and eventually they were unable to support the structure above. Astaneh-Asl also suggested that the fireproofing became dislodged during the initial aircraft impacts. He also explained that, once the initial structural failure occurred, progressive collapse of the entire structure was inevitable. César Pelli, who designed the Petronas Towers in Malaysia and the World Financial Center in New York, remarked, "no building is prepared for this kind of stress."

On September 13, 2001, Zdeněk P. Bažant, professor of civil engineering and materials science at Northwestern University, circulated a draft paper with results of a simple analysis of the World Trade Center collapse. Bažant suggested that heat from the fires was a key factor, causing steel columns in both the core and the perimeter to weaken and experience deformation before losing their carrying capacity and buckling. Once more than half of the columns on a particular floor buckled, the overhead structure could no longer be supported and complete collapse of the structures occurred. Bažant later published an expanded version of this analysis. Other analyses were conducted by MIT civil engineers Oral Buyukozturk and Franz-Josef Ulm, who also described a collapse mechanism on September 21, 2001. They later contributed to an MIT collection of papers on the WTC collapses edited by Eduardo Kausel called The Towers Lost and Beyond.

Immediately following the collapses, there was some confusion about who had the authority to carry out an official investigation. While there are clear procedures for the investigation of aircraft accidents, no agency had been appointed in advance to investigate building collapses. A team was quickly assembled by the Structural Engineers Institute of the American Society of Civil Engineers, led by W. Gene Corley, Senior Vice President of CTLGroup. It also involved the American Institute of Steel Construction, the American Concrete Institute, the National Fire Protection Association, and the Society of Fire Protection Engineers. ASCE ultimately invited FEMA to join the investigation, which was completed under the auspices of the latter.

The investigation was criticized by some engineers and lawmakers in the U.S. It had little funding, no authority to demand evidence, and limited access to the WTC site. One major point of contention at the time was that the cleanup of the WTC site was resulting in the destruction of the majority of the buildings' steel components. Indeed, when NIST published its final report, it noted "the scarcity of physical evidence" that it had had at its disposal to investigate the collapses. Only a fraction of a percent of the buildings remained for analysis after the cleanup was completed: some 236 individual pieces of steel, although 95% of structural beams and plates and 50% of the reinforcement bars were recovered.

FEMA published its report in May 2002. While NIST had already announced its intention to investigate the collapses in August of the same year, by September 11, 2002 (a year after the disaster), there was growing public pressure for a more thorough investigation. Congress passed the National Construction Safety Team bill in October 2002, giving NIST the authority to conduct an investigation of the World Trade Center collapses.

FEMA building performance study
FEMA suggested that fires in conjunction with damage resulting from the aircraft impacts were the key to the collapse of the towers. Thomas Eagar, Professor of Materials Engineering and Engineering Systems at MIT, described the fires as "the most misunderstood part of the WTC collapse". This is because the fires were originally said to have "melted" the floors and columns. Jet fuel is essentially kerosene and would have served mainly to ignite very large, but not unusually hot, hydrocarbon fires. As Eagar said, "The temperature of the fire at the WTC was not unusual, and it was most definitely not capable of melting steel." This led Eagar, FEMA and others to focus on what appeared to be the weakest point of the structures, namely, the points at which the floors were attached to the building frame.

NIST report
After the FEMA report had been published, and following pressure from technical experts, industry leaders and families of victims, the Commerce Department's National Institute of Standards and Technology conducted a three-year, $16 million investigation into the structural failure and progressive collapse of several WTC complex structures. The study included in-house technical expertise, along with assistance from several outside private institutions, including the Structural Engineering Institute of the American Society of Civil Engineers, Society of Fire Protection Engineers, National Fire Protection Association, American Institute of Steel Construction, Simpson Gumpertz & Heger Inc., Council on Tall Buildings and Urban Habitat, and the Structural Engineers Association of New York.

The scope of the NIST investigation was focused on identifying "the sequence of events" that triggered the collapse, and did not include detailed analysis of the collapse mechanism itself (after the point at which events made the collapse inevitable). In line with the concerns of most engineers, NIST focused on the airplane impacts and the spread and effects of the fires, modeling these using Fire Dynamics Simulator software. NIST developed several highly detailed structural models for specific sub-systems such as the floor trusses as well as a global model of the towers as a whole which is less detailed. These models were static or quasi-static, including deformation but not the motion of structural elements after rupture.

James Quintiere, professor of fire protection engineering at the University of Maryland, called the fact that only a small portion of the building's steel was preserved for study "a gross error" that NIST should have openly criticized. He also noted that the report lacked a timeline and physical evidence to support its conclusions. Some engineers have suggested that understanding of the collapse mechanism could be improved by developing an animated sequence of the collapses based on a global dynamic model, and comparing it with the video evidence of the actual collapses. The NIST report for WTC 7 concluded that no blast sounds were heard on audio and video footage, or were reported by witnesses.

7 World Trade Center

In May 2002, FEMA issued a report on the collapse based on a preliminary investigation conducted jointly with the Structural Engineering Institute of the American Society of Civil Engineers under leadership of Dr. W. Gene Corley, P.E. FEMA made preliminary findings that the collapse was not primarily caused by actual impact damage from the collapse of 1 WTC and 2 WTC but by fires on multiple stories ignited by debris from the other two towers that continued unabated due to lack of water for sprinklers or manual firefighting. The report did not reach conclusions about the cause of the collapse and called for further investigation.

In response to FEMA's concerns, the National Institute of Standards and Technology (NIST) was authorized to lead an investigation into the structural failure and collapse of the World Trade Center twin towers and 7 World Trade Center. The investigation, led by Dr S. Shyam Sunder, drew not only upon in-house technical expertise, but also upon the knowledge of several outside private institutions, including the Structural Engineering Institute of the American Society of Civil Engineers (SEI/ASCE), the Society of Fire Protection Engineers (SFPE), the National Fire Protection Association (NFPA), the American Institute of Steel Construction (AISC), the Council on Tall Buildings and Urban Habitat (CTBUH), and the Structural Engineers Association of New York (SEAoNY).

The bulk of the investigation of 7 World Trade Center was delayed until after reports were completed on the collapse of the World Trade Center twin towers. In the meantime, NIST provided a preliminary report about 7 World Trade Center in June 2004, and thereafter released occasional updates on the investigation. According to NIST, the investigation of 7 World Trade Center was delayed for a number of reasons, including that NIST staff who had been working on 7 World Trade Center were assigned full-time from June 2004 to September 2005 to work on the investigation of the collapse of the twin towers. In June 2007, Shyam Sunder explained, "We are proceeding as quickly as possible while rigorously testing and evaluating a wide range of scenarios to reach the most definitive conclusion possible. The 7 WTC investigation is in some respects just as challenging, if not more so, than the study of the towers. However, the current study does benefit greatly from the significant technological advances achieved and lessons learned from our work on the towers." In November 2008, NIST released its final report on the causes of the collapse of 7 World Trade Center. This followed their August 21, 2008 draft report which included a period for public comments. In its investigation, NIST utilized ANSYS to model events leading up to collapse initiation and LS-DYNA models to simulate the global response to the initiating events. NIST determined that diesel fuel did not play an important role, nor did the structural damage from the collapse of the twin towers, nor did the transfer elements (trusses, girders, and cantilever overhangs), but the lack of water to fight the fire was an important factor. The fires burned out of control during the afternoon, causing floor beams near Column 79 to expand and push a key girder off its seat, triggering the floors to fail around column 79 on Floors 8 to 14. With a loss of lateral support across nine floors, Column 79 soon buckled – pulling the East penthouse and nearby columns down with it. With the buckling of these critical columns, the collapse then progressed east-to-west across the core, ultimately overloading the perimeter support, which buckled between Floors 7 and 17, causing the entire building above to fall downward as a single unit. From collapse timing measurements taken from a video of the north face of the building, NIST observed that the building's exterior facade fell at free fall acceleration through a distance of approximately 8 stories (32 meters, or 105 feet), noting "the collapse time was approximately 40 percent longer than that of free fall for the first 18 stories of descent." The fires, fueled by office contents, along with the lack of water, were the key reasons for the collapse.

The collapse of the old 7 World Trade Center is remarkable because it was the first known instance of a tall building collapsing primarily as a result of uncontrolled fires. Based on its investigation, NIST reiterated several recommendations it had made in its earlier report on the collapse of the twin towers, and urged immediate action on a further recommendation: that fire resistance should be evaluated under the assumption that sprinklers are unavailable; and that the effects of thermal expansion on floor support systems be considered. Recognizing that current building codes are drawn to prevent loss of life rather than building collapse, the main point of NIST's recommendations is that buildings should not collapse from fire even if sprinklers are unavailable.

Other investigations
In 2003, Asif Usmani, Professor of Structural Engineering at University of Edinburgh, published a paper with two colleagues. They provisionally concluded the fires alone, without any damage from the airplanes, could have been enough to bring down the buildings. In their view, the towers were uniquely vulnerable to the effects of large fires on several floors at the same time. When the NIST report was published, Barbara Lane, with the UK engineering firm Arup, criticized its conclusion that the loss of fire proofing was a necessary factor in causing the collapses; "We have carried out computer simulations which show that the towers would have collapsed after a major fire on three floors at once, even with fireproofing in place and without any damage from plane impact." Jose L. Torero, formerly of the BRE Centre for Fire Safety Engineering at the University of Edinburgh, pursued further research into the potentially catastrophic effects of fire on real-scale buildings.

Cleanup
The cleanup was a massive operation coordinated by the City of New York Department of Design and Construction. On September 22, a preliminary cleanup plan was delivered by Controlled Demolition, Inc. (CDI) of Phoenix, Maryland. Costing hundreds of millions of dollars, it involved round-the-clock operations with many contractors and subcontractors. By early November, with a third of the debris removed, officials began to reduce the number of firefighters and police officers assigned to recovering the remains of victims, in order to prioritize the removal of debris. This caused confrontations with firefighters. Despite efforts to extinguish the blaze, the large pile of debris burned for three months, until the majority of the rubble was finally removed from the site. In 2007, the demolition of the surrounding damaged buildings was still ongoing as new construction proceeded on the World Trade Center's replacement, One World Trade Center.

Health effects
The collapse of the World Trade Center produced enormous clouds of dust that covered Manhattan for days. On September 18, 2001, the United States Environmental Protection Agency (EPA) assured the public that the air in Manhattan was "safe to breathe". In 2003 the EPA's inspector general found that the agency did not at that time have sufficient data to make such a statement. Dust from the collapse seriously reduced air quality and is likely the cause of many respiratory illnesses in lower Manhattan. Asbestosis is such an illness, and asbestos would have been present in the dust. Significant long term medical and psychological effects have been found among first responders including elevated levels of asthma, sinusitis, gastroesophageal reflux disease and post-traumatic stress disorder.

Health effects also extended to residents, students, and office workers of Lower Manhattan and nearby Chinatown. Several deaths have been linked to the toxic dust, and the victims' names will be included in the World Trade Center memorial. More than 18,000 people have suffered from illnesses from the dust.

title: Collapse of the World Trade Center


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Great Smoky Mountains

The Great Smoky Mountains (ᎡᏆ ᏚᏧᏍᏚ ᏙᏓᎸ, Equa Dutsusdu Dodalv) are a mountain range rising along the Tennessee–North Carolina border in the southeastern United States. They are a subrange of the Appalachian Mountains and form part of the Blue Ridge Physiographic Province. The range is sometimes called the Smoky Mountains, and the name is commonly shortened to the Smokies. The Smokies are best known as the home of the Great Smoky Mountains National Park, which protects most of the range. The park was established in 1934 and, with over 11 million visits per year, is the most visited national park in the United States.

The Smokies are part of an International Biosphere Reserve. The range is home to an estimated 187000 acre of old-growth forest, constituting the largest such stand east of the Mississippi River. The coves hardwood forests in the range's lower elevations are among the most diverse ecosystems in North America, and the Southern Appalachian spruce–fir forest that covers the upper elevations is the largest of its kind. The Smokies are home to the densest black bear population in the Eastern United States and the most diverse salamander population outside of the tropics.

Along with the biosphere reserve, the Great Smoky Mountains have been designated a UNESCO World Heritage Site. The U.S. National Park Service preserves and maintains 78 structures within the national park that were once part of the numerous small Appalachian communities scattered throughout the range's river valleys and coves. The park contains five historic districts and nine individual listings on the National Register of Historic Places.

The name "Smoky" comes from the natural fog that often hangs over the range and presents as large smoke plumes from a distance. This fog is caused by the vegetation emitting volatile organic compounds, chemicals that have a high vapor pressure and easily form vapors at normal temperature and pressure.

Geography

The Great Smoky Mountains stretch from the Pigeon River in the northeast to the Little Tennessee River in the southeast. The northwestern half of the range gives way to a series of elongate ridges known as the "Foothills," the outermost of which include Chilhowee Mountain and English Mountain. The range is roughly bounded on the south by the Tuckasegee River and to the southeast by Soco Creek and Jonathan Creek. The Smokies comprise parts of Blount County, Sevier County, and Cocke County in Tennessee and Swain County and Haywood County in North Carolina.

The sources of several rivers are located in the Smokies, including the Little Pigeon River, the Oconaluftee River, and Little River. Streams in the Smokies are part of the Tennessee River watershed and are thus entirely west of the Eastern Continental Divide. The largest stream entirely within the park is Abrams Creek, which rises in Cades Cove and empties into the Chilhowee Lake impoundment of the Little Tennessee River near Chilhowee Dam.

Other major streams include Hazel Creek and Eagle Creek in the southwest, Raven Fork near Oconaluftee, Cosby Creek near Cosby, and Roaring Fork near Gatlinburg. The Little Tennessee River passes through five impediments along the range's southwestern boundary, namely Tellico Lake, Chilhowee Lake, Calderwood Lake, Cheoah Lake, and Fontana Lake.

Notable peaks
The highest point in the Smokies is Clingmans Dome, the tallest mountain in Tennessee, which rises to an elevation of 6643 ft. It has the range's highest topographic prominence at 4503 ft. Mount Le Conte is the tallest (i.e., from immediate base to summit) mountain in the range, rising 5301 ft from its base in Gatlinburg to its 6593 ft summit.

Climate
The Smokies rise prominently above the surrounding low terrain. For example, Mount Le Conte (6593 feet) rises more than a mile (1.6 km) above its base. Because of their prominence, the Smokies receive a heavy annual amount of precipitation. Annual precipitation amounts range from 50 to 80 inch, and snowfall in the winter can be heavy, especially on the higher slopes. For comparison, the surrounding terrain has annual precipitation of around 40 to 50 inch. Flash flooding often occurs after heavy rain.

In 2004, the remnants of Hurricane Frances caused major flooding, landslides, and high winds, which were soon followed by Hurricane Ivan, making the situation worse. Other post-hurricanes, including Hurricane Hugo in 1989, have caused similar damage in the Smokies.

As for temperatures, the average temperature difference between the mountains (Newfound Gap around 5000 feet MSL and the valleys (Park Headquarters around 1600 feet MSL in the Great Smoky Mountains National Park is between 10 and 13 °F (6 and 7 °C) with highs and between 3 and 6 °F (2 and 3 °C) with lows. The difference between high temperatures is similar to the moist adiabatic lapse rate (3.3 degrees Fahrenheit per 1,000 ft), while the smaller difference between low temperatures is the result of frequent temperature inversions developing in the morning, especially during autumn.

Strong damaging winds (80 to 100 mph, or sometimes greater) are observed a few times each year around the Smoky Mountains during the cool season (October through April), as a result of a phenomenon known as mountain waves. These mountain wave winds are strongest in a narrow area along the foothills and can create extensive areas of fallen trees and roof damage, especially around Cades Cove in the Great Smoky Mountains National Park and the Camp Creek community. Strong winds created by mountain waves were a contributing factor with the devastating Gatlinburg fire on November 28, 2016 during the 2016 Great Smoky Mountains wildfires. Damaging winds can also be generated by strong thunderstorms, with tornadoes and strong thunderstorm complexes (also known as mesoscale convective systems) occasionally affecting the Smoky Mountains.

The climate of Clingmans Dome is hemiboreal (Köppen Dfb, Trewartha Dcb ). As with much of the southern Blue Ridge, the area qualifies as part of the Appalachian Rainforest. On the other hand, Gatlinburg's climate is four-season subtropical (Cfa) under Köppen (oceanic Do under Trewartha), typical of Tennessee.

Geology

Most of the rocks in the Great Smoky Mountains consist of Late Precambrian rocks that are part of a formation known as the Ocoee Supergroup. The Ocoee Supergroup consists primarily of slightly metamorphosed sandstones, phyllites, schists, and slate. Early Precambrian rocks, which include the oldest rocks in the Smokies, comprise the dominant rock type in the Raven Fork Valley (in the Oconaluftee valley) and lower Tuckasegee River between Cherokee and Bryson City. They consist primarily of metamorphic gneiss, granite, and schist. Cambrian sedimentary rocks are found among the outer reaches of the Foothills to the northwest and in limestone coves such as Cades Cove.

The Precambrian gneiss and schists—the oldest rocks in the Smokies—formed over a billion years ago from the accumulation of marine sediments and igneous rock in a primordial ocean. In the Late Precambrian period, this ocean expanded, and the more recent Ocoee Supergroup rocks formed from accumulations of the eroding land mass onto the ocean's continental shelf.

By the end of the Paleozoic era, the ancient ocean had deposited a thick layer of marine sediments which left behind sedimentary rocks such as limestone. During the Ordovician period, the North American and African plates collided, destroying the ancient ocean and initiating the Alleghenian orogeny—the mountain-building epoch that created the Appalachian range. The Mesozoic era saw the rapid erosion of the softer sedimentary rocks from the new mountains, re-exposing the older Ocoee Supergroup formations.

Around 20,000 years ago, subarctic glaciers advanced southward across North America, and although they never reached the Smokies, the advancing glaciers led to colder mean annual temperatures and an increase in precipitation throughout the range. Trees were unable to survive at the higher elevations and were replaced by tundra vegetation. Spruce-fir forests occupied the valleys and slopes below approximately 4950 ft. The persistent freezing and thawing during this period created the large blockfields that are often found at the base of large mountain slopes.

Between 16,500 and 12,500 years ago, the glaciers to the north retreated and mean annual temperatures rose. The tundra vegetation disappeared, and the spruce-fir forests retreated to the highest elevations. Hardwood trees moved into the region from the coastal plains, replacing the spruce-fir forests in the lower elevations. The temperatures continued warming until around 6,000 years ago, when they began to gradually grow cooler.

Flora
Heavy logging in the late 19th century and early 20th century devastated much of the forests of the Smokies, but the National Park Service estimates 187000 acre of old-growth forest remains, comprising the largest old-growth stand in the Eastern United States. Most of the forest is a mature second-growth hardwood forest. The range's 1,600 species of flowering plants include over 100 species of native trees and 100 species of native shrubs. The Smokies are also home to over 450 species of non-vascular plants and 2,000 species of fungi.

The forests of the Smokies are typically divided into three zones:
 * The cove hardwood forests in the stream valleys, coves, and lower mountain slopes
 * The northern hardwood forests on the higher mountain slopes
 * The spruce-fir or boreal forest at the very highest elevations

Appalachian balds—patches of land where trees are unexpectedly absent or sparse—are interspersed through the mid-to-upper elevations in the range. Balds include grassy balds, which are highland meadows covered primarily by thick grasses, and heath balds, which are dense thickets of rhododendron and mountain laurel typically occurring on narrow ridges. Mixed oak-pine forests are found on dry ridges, especially on the south-facing North Carolina side of the range. Stands dominated by the Eastern hemlock (Tsuga canadensis) are occasionally found along streams and broad slopes above 3500 ft.

Cove hardwood forest

Cove hardwood forests, which are native to southern Appalachia, are among the most diverse forest types in North America. The cove hardwood forests of the Smokies are mostly second-growth, although some 72000 acre are still old-growth. The Albright Grove along the Maddron Bald Trail (between Gatlinburg and Cosby) is an accessible old-growth forest with some of the oldest and tallest trees in the entire range.

Over 130 species of trees are found among the canopies of the cove hardwood forests in the Smokies. The dominant species include yellow birch (Betula alleghaniensis), basswood (Tilia americana), yellow buckeye (Aesculus flava), tulip tree (Liriodendron tulipifera; commonly called "tulip poplar"), silverbells (Halesia carolina), sugar maple (Acer saccharum), cucumber magnolia (Magnolia acuminata), shagbark hickory (Carya ovata), Carolina hemlock (Tsuga caroliniana) and eastern hemlock (Tsuga canadensis). The American chestnut (Castanea dentata), which was arguably the most beloved tree of the range's pre-park inhabitants, was killed off by the introduced Chestnut blight in the 1920s.

The understories of the cove hardwood forest contain dozens of species of shrubs and vines. Dominant species in the Smokies include the Eastern redbud (Cercis canadensis), flowering dogwood (Cornus florida), Catawba rhododendron (Rhododendron catawbiense), mountain laurel (Kalmia latifolia), and smooth hydrangea (Hydrangea arborescens).

Northern hardwood forest

The mean annual temperatures in the higher elevations in the Smokies are cool enough to support forest types more commonly found in the northern United States. The northern hardwood forests constitute the highest broad-leaved forest in the eastern United States. About 28600 acre are old-growth.

In the Smokies, the northern hardwood canopies are dominated by yellow birch (Betula alleghaniensis) and American beech (Fagus grandifolia). White basswood (Tilia heterophylla), mountain maple (Acer spicatum) and striped maple (Acer pensylvanicum), and yellow buckeye (Aesculus flava) are also present. The understory is home to diverse species such as coneflower, skunk goldenrod, Rugels ragwort, bloodroot, hydrangea, and several species of grasses and ferns.

A unique community is the beech gap, or beech orchard. Beech gaps consist of high mountain gaps that have been monopolized by beech trees. The beech trees are often twisted and contorted by the high winds that occur in these gaps. Why other tree types such as the red spruce fail to encroach into the beech gaps is unknown.

Spruce-fir forest

The Southern Appalachian spruce–fir forest—also called the "boreal" or "Canadian" forest—is a relict of the ice ages, when mean annual temperatures in the Smokies were too cold to support a hardwood forest. While the rise in temperatures between 12,500 and 6,000 years ago allowed the hardwoods to return, the spruce-fir forest has managed to survive on the harsh mountain tops, typically above 5500 ft. About 10600 acre of the spruce-fir forest are old-growth.

The spruce-fir forest consists primarily of two conifer species—red spruce (Picea rubens) and Fraser fir (Abies fraseri). The Fraser firs, which are native to southern Appalachia, once dominated elevations above 6200 ft in the Smokies. Most of these firs were killed, however, by an infestation of the balsam wooly adelgid, which arrived in the Smokies in the early 1960s. Thus, red spruce is now the dominant species in the range's spruce-fir forest. Large stands of dead Fraser firs remain atop Clingmans Dome and on the northwestern slopes of Old Black. While much of the red spruce stands were logged in the 1910s, the tree is still common throughout the range above 5500 ft. Some of the red spruces are believed to be 300 years old, and the tallest rise to over 100 ft.

The main difference between the Southern Appalachian spruce–fir forest and the spruce-fir forests in northern latitudes is the dense broad-leaved understory of the former, which are home to catawba rhododendron, mountain ash, pin cherry, thornless blackberry, and hobblebush. The herbaceous and litter layers are poorly lit year-round and are thus dominated by shade-tolerant plants such as ferns, namely mountain wood fern and northern lady fern, and over 280 species of mosses.

Wildflowers

Many wildflowers grow in mountains and valleys, including bee balm, Solomon's seal, Dutchman's breeches, various trilliums, the Dragon's Advocate and even hardy orchids. There are two native species of rhododendron in the area. The catawba rhododendron has purple flowers in May and June, while the rosebay rhododendron has longer leaves and white or light pink blooms in June and July.

The orange- to sometimes red-flowered and deciduous flame azalea closely follows along with the catawbas. The closely related mountain laurel blooms in between the two, and all of the blooms progress from lower to higher elevations. The reverse is true in autumn, when nearly bare mountaintops covered in rime ice (frozen fog) can be separated from green valleys by very bright and varied leaf colors. The rhododendrons are broadleafs, whose leaves droop in order to shed wet and heavy snows that come through the region during winter.

Fauna

The Great Smoky Mountains are home to 66 species of mammals, over 240 species of birds, 43 species of amphibians, 60 species of fish, and 40 species of reptiles. The range has the densest black bear population east of the Mississippi River. The black bear has come to symbolize wildlife in the Smokies, and the animal frequently appears on the covers of the Great Smoky Mountains National Park's literature. Most of the range's adult eastern black bears weigh between 100 lb and 300 lb, although some grow to more than 500 lb.

Other mammals include the white-tailed deer, the population of which drastically expanded with the creation of the national park. The bobcat is the only remaining wild cat species, although sightings of cougars, which once thrived in the area, are still occasionally reported. The coyote is not believed to be native to the range but has moved into the area in recent years and is treated as a native species. Two species of fox (red fox and the gray fox) are found within the Smokies, with red foxes being documented at all elevations.

European boar, introduced as game animals in the early 20th century, thrive in southern Appalachia but are considered a nuisance because of their tendency to root up and destroy plants. The boars are seen as taking food resources away from bears as well, and the park service has sponsored a program that pays individuals to hunt and kill boars and leave their bodies in locations frequented by bears.

The Smokies are home to over two dozen species of rodents, including the endangered northern flying squirrel and 10 species of bats, including the endangered Indiana bat. The National Park Service has successfully reintroduced river otters and elk. An attempt to reintroduce the red wolf in the early 1990s ultimately failed. These wolves were removed from the park and relocated to the Alligator River National Wildlife Refuge in North Carolina.

The Smokies are home to a diverse bird population due to the presence of multiple forest types. Species that thrive in southern hardwood forests, such as the red-eyed vireo, wood thrush, wild turkey, northern parula, ruby-throated hummingbird, and tufted titmouse, are found throughout the lower elevations and cove hardwood forests. Species more typical of cooler climates, such as the raven, winter wren, black-capped chickadee, yellow-bellied sapsucker, dark-eyed junco, and Blackburnian, chestnut-sided, and Canada warblers, are found in the sruce-fir and northern hardwood zones.

Ovenbirds, whip-poor-wills, and downy woodpeckers live in the drier pine-oak forests and heath balds. Bald eagles and golden eagles have been spotted at all elevations in the park. Peregrine falcon sightings are also not uncommon, and a peregrine falcon eyrie is known to have existed near Alum Cave Bluffs throughout the 1930s. Red-tailed hawks, the most common hawk species, have been sighted at all elevations. Owl species include the barred owl, eastern screech owl, and northern saw-whet owl.

Timber rattlesnakes—one of two venomous snake species in the Smokies—are found at all elevations. The other venomous snake, the copperhead, is typically found at lower elevations. Other reptiles include the eastern box turtle, the eastern fence lizard, the black rat snake, and the northern water snake.

The Smokies are home to one of the world's most diverse salamander populations. Five of the world's nine families of salamanders are found in the range, consisting of up to 31 species. The red-cheeked salamander is found only in the Smokies. The imitator salamander is found only in the Smokies and the nearby Plott Balsams and Great Balsam Mountains. Two other species—the southern gray-cheeked salamander and the southern Appalachian salamander—occur only in the general region. Other species include the shovelnose salamander, blackbelly salamander, eastern red-spotted newt, and spotted dusky salamander. The hellbender inhabits swift streams. Other amphibians include the American toad and the American bullfrog, wood frog, upland chorus frog, northern green frog, and spring peeper.

Fish include trout, lamprey, darter, shiner, bass, and sucker. The brook trout is the only trout species native to the range, although northwestern rainbow trout and European brown trout were introduced in the first half of the 20th century. The larger rainbow and brown trout outcompete the native brook trout for food and habitat at lower elevations. As such, most of the brook trout found in the park today are in streams above 3,000 feet in elevation. Trout generally smaller than in different locales. Protected fish species include the smoky madtom and yellowfin madtom, the spotfin chub, and the duskytail darter.

The firefly Photinus carolinus, whose synchronized flashing light displays occur in mid-June, is native to the Smoky Mountains with a population epicenter near Elkmont, Tennessee.

Ecosystem threats

Air pollution is contributing to increased red spruce tree mortality at higher elevations and oak decline at lower elevations, while invasive hemlock woolly adelgids attack hemlocks, and balsam woolly adelgids attack Fraser firs. Pseudoscymnus tsugae, a type of beetle in the ladybug family, Coccinellidae, has been introduced in an attempt to control the pests.

Visibility is dramatically reduced by smog from both the Southeastern United States and the Midwest, and smog forecasts are prepared daily by the Environmental Protection Agency for both nearby Knoxville, Tennessee and Asheville, North Carolina.

Environmental threats are the concern of many non-profit environmental stewardship groups, especially The Friends of the Smokies. Formed in 1993, the group assists the National Park Service in its mission to preserve and protect the Great Smoky Mountains National Park by raising funds and public awareness, and providing volunteers for needed projects.

Prehistory
Native Americans have likely been hunting in the Great Smoky Mountains for 14,000 years. Numerous Archaic period (c. 8000–1000 B.C.) artifacts have been found within the national park's boundaries, including projectile points uncovered along likely animal migration paths. Woodland period (c. 1000 B.C. - 1000 A.D.) sites found within the park contained 2,000-year-old ceramics and evidence of primitive agriculture.

The increasing reliance upon agriculture during the Mississippian period (c. 900–1600 A.D.) lured Native Americans away from the game-rich forests of the Smokies and into the fertile river valleys on the outer fringe of the range. Substantial Mississippian-period villages were uncovered at Citico and Toqua (named after the Cherokee villages that later thrived at these sites) along the Little Tennessee River in the 1960s. Fortified Mississippian-period villages have been excavated at the McMahan Indian Mounds in Sevierville and as well as mounds in Townsend.

Most of these villages were part of a minor chiefdom centered on a large village known as Chiaha, which was located on an island now submerged by Douglas Lake. The 1540 expedition of Hernando de Soto and the 1567 expedition of Juan Pardo passed through the French Broad River valley north of the Smokies, both spending a considerable amount of time at Chiaha. The Pardo expedition followed a trail across the flanks of Chilhowee Mountain to the Mississippian-period villages at Chilhowee and Citico (Pardo's notary called them by their Muskogean names, "Chalahume" and "Satapo").

Cherokee
By the time the first English explorers arrived in southern Appalachia in the late 17th century, the Cherokee controlled much of the region, and the Great Smoky Mountains lay at the center of their territory. One Cherokee legend tells of a magical lake hidden deep within the range but inaccessible to humans. Another tells of a captured Shawnee medicine man named Aganunitsi who, in exchange for his freedom, travels to the remote sections of the range in search of the Uktena. The Cherokee called Gregory Bald Tsitsuyi ᏥᏧᏱ, or "rabbit place," and believed the mountain to be the domain of the Great Rabbit. Other Cherokee place names in the Smokies included Duniskwalgunyi ᏚᏂᏍᏆᎫᏂ, or "forked antlers", which refers to the Chimney Tops, and kuwahi ᎫᏩᎯ, or "mulberry place", which refers to Clingmans Dome.

Most Cherokee settlements were located in the river valleys on the outer fringe of the Smokies, which along with the Unicoi Mountains provided the main bulwark dividing the Overhill Cherokee villages in modern Tennessee from the Cherokee Middle towns in modern North Carolina. The Overhill town of Chilhowee was situated at the confluence of Abrams Creek and the Little Tennessee, and the Overhill town of Tallassee was located just a few miles upstream near modern Calderwood (both village sites are now under Chilhowee Lake). A string of Overhill villages, including Chota and Tanasi, dotted the Little Tennessee valley north of Chilhowee.

The Cherokee Middle towns included the village of Kittowa (which the Cherokee believed to be their oldest village) along the Tuckasegee River near Bryson City. The village of Oconaluftee, which was situated along the Oconaluftee River near the modern Oconaluftee Visitor Center, was the only known permanent Cherokee village located within the national park's boundaries. Sporadic or seasonal settlements were located in Cades Cove and the Hazel Creek valley.

European settlement

European explorers and settlers began arriving in Western North Carolina and East Tennessee in the mid-18th century. The influx of settlers at the end of the French and Indian War brought conflict with the Cherokee, who still held legal title to much of the land. When the Cherokee aligned themselves with the British at the outbreak of the American Revolution in 1776, American forces launched an invasion of Cherokee territory.

The Middle towns, including Kittuwa, were burned by General Griffith Rutherford, and several of the Overhill towns were burned by John Sevier. By 1805, the Cherokee had ceded control of the Smokies to the U.S. government. Although much of the tribe was forced west along the Trail of Tears in 1838, a few—largely through the efforts of William Holland Thomas—managed to retain their land on the Qualla Boundary and today comprise the Eastern Band of Cherokee Indians.

In the 1780s, several frontier outposts had been established along the outskirts of the Smokies, namely Whitson's Fort in what is now Cosby and Wear's Fort in what is now Pigeon Forge. Permanent settlers began arriving in these areas in the 1790s. In 1801, the Whaley brothers, William and John, moved from North Carolina to become the first settlers in what is now the Greenbrier section of the park.

In 1802, Edgefield, South Carolina resident William Ogle arrived in White Oak Flats where he cut and prepared logs for cabin construction. Although Ogle died shortly after returning to Edgefield, his wife, Martha Jane Huskey, eventually returned with her family and several other families to White Oak Flats, becoming the first permanent settlers in what would eventually become Gatlinburg. Their children and grandchildren spread out southward into the Sugarlands and Roaring Fork areas.

Cades Cove was settled largely by families who had purchased lots from land speculator William "Fighting Billy" Tipton. The first of these settlers, John and Lucretia Oliver, arrived in 1818. Two Cades Cove settlers, Moses and Patience Proctor, crossed over to the North Carolina side of the Smokies in 1836 to become the first Euro-American settlers in the Hazel Creek area. The Cataloochee area was first settled by the Caldwell family, who migrated to the valley in 1834.

Like most of southern Appalachia, the early 19th-century economy of the Smokies relied on subsistence agriculture. The average farm consisted of roughly 50 acre, part of which was cultivated and part of which was woodland. Early settlers lived in 16 ft x 20 ft log cabins, although these were replaced by more elaborate log houses and eventually, as lumber became available, by modern frame houses. Most farms included at least one barn, a springhouse (used for refrigeration), a smokehouse (used for curing meat), a chicken coop (protected chickens from predators), and a corn crib (kept corn dry and protected it from rodents). Some of the more industrious farmers operated gristmills, general stores, and sorghum presses. Religion was a central theme in the lives of the early residents of the Smokies, and community life was typically centered on churches. Christian Protestantism—especially Primitive Baptists, Missionary Baptists, Methodists, and Presbyterians; dominated the religious culture of the region.

American Civil War
While both Tennessee and North Carolina joined the Confederacy at the outbreak of the American Civil War in 1861, Union sentiment in the Great Smoky Mountains was much stronger relative to other regions in these two states. Generally, the communities on the Tennessee side of the Smokies supported the Union, while communities on the North Carolina side supported the Confederates. On the Tennessee side, 74% of Cocke Countians, 80% of Blount Countians, and 96% of Sevier Countians voted against secession. In the North Carolina Smokies—Cherokee, Haywood, Jackson, and Macon counties—about 46% of the population favored secession.

While no major engagements took place in the Smokies, minor skirmishes were fairly common. Cherokee chief William Holland Thomas formed a Confederate legion made up mostly of Cherokee soldiers. Thomas' Legion crossed the Smokies in 1862 and occupied Gatlinburg for several months to protect saltpeter mines atop Mount Le Conte. Residents of predominantly Union Cades Cove and predominantly Confederate Hazel Creek routinely crossed the mountains to steal one another's livestock. Residents of Cosby and Cataloochee did likewise. One notable Civil War incident was the murder of long-time Cades Cove resident Russell Gregory (for whom Gregory Bald is named), which was carried out by bushwhackers in 1864 shortly after Gregory had led an ambush that routed a band of Confederates seeking to wreak havoc in the cove. Another incident was George Kirk's raid on Cataloochee, in which Kirk killed or wounded 15 Union soldiers recovering at a makeshift hospital.

Logging

While selective logging occurred in the Great Smoky Mountains throughout the 19th century, the general inaccessibility of the forests prevented major logging operations, and lumber firms relied on the lowland forests in the northeastern United States and the Mississippi Delta in the southeast. As timber resources in these regions became exhausted, and as the demand for lumber skyrocketed after the Civil War, entrepreneurs began looking for ways to reach the virgin forests of southern Appalachia. The first logging operations in the Smokies, which began in the 1880s, used splash dams or booms to float logs down rivers to lumber mills in nearby cities. Notable splash dam and boom operations included the English Lumber Company on Little River, the Taylor and Crate operations along Hazel Creek, and the ambitious operations of Alexander Arthur on the Pigeon River. All three of these operations failed within their first few years, however, after their dams and boom systems were destroyed by floods.

Innovations in logging railroads and band saw technology in the late 19th century made large-scale logging possible in the mountainous areas of southern Appalachia. The largest logging operation in the Smokies was the Little River Lumber Company, which logged the Little River watershed between 1901 and 1939. The company also established company towns at Townsend (named for the company's chief owner and manager, Wilson B. Townsend), Elkmont, and Tremont.

The second-largest operation was the Ritter Lumber Company, which logged the Hazel Creek watershed between 1907 and 1928. Ruins of Ritter's lumbering operations are still visible along the Hazel Creek Trail. Other lumbering operations included Three M Lumber and Champion Fibre, both of which logged the Oconaluftee watershed. By the time all operations ceased in the 1930s, logging firms had removed two-thirds of the virgin forests from the Smokies. According to the National Park Service, 80% of the Smokies was clear cut in the early 20th century.

National park
Wilson B. Townsend, the head of Little River Lumber, began advertising Elkmont as a tourist destination in 1909. Within a few years, the Wonderland Hotel and the Appalachian Club had been established to cater to elite Knoxvillians seeking summer mountain getaways. In the early 1920s, several Appalachian Club members, among them Knoxville businessman Colonel David Chapman, began seriously considering a movement to establish a national park in the Smokies. As head of the Great Smoky Mountains Park Commission, Chapman was largely responsible for raising funds for land purchases and coordinating park efforts between local, state, and federal entities.

The creation of the Great Smoky Mountains National Park proved much more complex than the creation of its predecessors, such as Yellowstone and Yosemite, which were already federally owned. Along with convincing logging firms to sell lucrative lumber rights, the Park Commission had to negotiate the purchase of thousands of small farms and remove entire communities. The commission also had to deal with the Tennessee and North Carolina legislatures, which at times were opposed to spending taxpayer money on park efforts. In spite of these difficulties, the Park Commission had completed most major land purchases by 1932. The national park officially opened in 1934, with President Franklin D. Roosevelt presiding over the opening ceremony at Newfound Gap.

Culture and tourism

The culture of the area is that of southern Appalachia, and previously the Cherokee people. Tourism is key to the area's economy, particularly in cities like Pigeon Forge, Gatlinburg, and Cherokee. In 2006, the Great Smoky Mountains Heritage Center opened in Townsend with the mission of preserving various aspects of the region's culture. The Tennessee Smokies baseball team plays in Sevierville and is named for the mountain range.

The Great Smoky Mountains are home to The Gatlinburg SkyLift and SkyBridge. The SkyBridge is the longest skybridge in the United States, at about 680 feet long.

title: Great Smoky Mountains