Seeing Different Content

Grand Canyon

The Grand Canyon is part of the Colorado River basin which has developed over the past 70 million years,[13] in part based on apatite (U-Th)/He thermochronometry showing that Grand Canyon reached a depth near to the modern depth by 20 Ma.[14] A recent study examining caves near Grand Canyon places their origins beginning about 17 million years ago. Previous estimates had placed the age of the canyon at 5–6 million years.[15] The study, which was published in the journal Science in 2008, used uranium-lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon.[16] There is a substantial amount of controversy because this research suggests such a substantial departure from prior widely supported scientific consensus.[17] In December 2012, a study published in the journal Science claimed new tests had suggested the Grand Canyon could be as old as 70 million years.[18] However, this study has been criticized by those who support the "young canyon" age of around six million years as "[an] attempt to push the interpretation of their new data to their limits without consideration of the whole range of other geologic data sets."[15] The canyon is the result of erosion which exposes one of the most complete geologic columns on the planet. The major geologic exposures in the Grand Canyon range in age from the 2-billion-year-old Vishnu Schist at the bottom of the Inner Gorge to the 230-million-year-old Kaibab Limestone on the Rim. There is a gap of about a billion years between the 500-million-year-old stratum and the level below it, which dates to about 1.5 billion years ago. This large unconformity indicates a long period for which no deposits are present. Many of the formations were deposited in warm shallow seas, near-shore environments (such as beaches), and swamps as the seashore repeatedly advanced and retreated over the edge of a proto-North America. Major exceptions include the Permian Coconino Sandstone, which contains abundant geological evidence of aeolian sand dune deposition. Several parts of the Supai Group also were deposited in non–marine environments. The great depth of the Grand Canyon and especially the height of its strata (most of which formed below sea level) can be attributed to 5–10 thousand feet (1,500 to 3,000 m) of uplift of the Colorado Plateau, starting about 65 million years ago (during the Laramide Orogeny). This uplift has steepened the stream gradient of the Colorado River and its tributaries, which in turn has increased their speed and thus their ability to cut through rock (see the elevation summary of the Colorado River for present conditions). Weather conditions during the ice ages also increased the amount of water in the Colorado River drainage system. The ancestral Colorado River responded by cutting its channel faster and deeper. The base level and course of the Colorado River (or its ancestral equivalent) changed 5.3 million years ago when the Gulf of California opened and lowered the river's base level (its lowest point). This increased the rate of erosion and cut nearly all of the Grand Canyon's current depth by 1.2 million years ago. The terraced walls of the canyon were created by differential erosion.[19] Between 100,000 and 3 million years ago, volcanic activity deposited ash and lava over the area which at times completely obstructed the river. These volcanic rocks are the youngest in the canyon.


Source: https://en.wikipedia.org/wiki/Grand_Canyon

Eiffel Tower

The Eiffel Tower (/ˈaɪfəl/ EYE-fəl; French: Tour Eiffel [tuʁ‿ɛfɛl] (About this soundlisten)) is a wrought-iron lattice tower on the Champ de Mars in Paris, France. It is named after the engineer Gustave Eiffel, whose company designed and built the tower. Constructed from 1887–1889 as the entrance to the 1889 World's Fair, it was initially criticised by some of France's leading artists and intellectuals for its design, but it has become a global cultural icon of France and one of the most recognisable structures in the world.[3] The Eiffel Tower is the most-visited paid monument in the world; 6.91 million people ascended it in 2015. The tower is 324 metres (1,063 ft) tall, about the same height as an 81-storey building, and the tallest structure in Paris. Its base is square, measuring 125 metres (410 ft) on each side. During its construction, the Eiffel Tower surpassed the Washington Monument to become the tallest man-made structure in the world, a title it held for 41 years until the Chrysler Building in New York City was finished in 1930. Due to the addition of a broadcasting aerial at the top of the tower in 1957, it is now taller than the Chrysler Building by 5.2 metres (17 ft). Excluding transmitters, the Eiffel Tower is the second tallest free-standing structure in France after the Millau Viaduct. The tower has three levels for visitors, with restaurants on the first and second levels. The top level's upper platform is 276 m (906 ft) above the ground – the highest observation deck accessible to the public in the European Union. Tickets can be purchased to ascend by stairs or lift to the first and second levels. The climb from ground level to the first level is over 300 steps, as is the climb from the first level to the second. Although there is a staircase to the top level, it is usually accessible only by lift.


Source: https://en.wikipedia.org/wiki/Eiffel_Tower

Golden Gate Bridge

Although the idea of a bridge spanning the Golden Gate was not new, the proposal that eventually took hold was made in a 1916 San Francisco Bulletin article by former engineering student James Wilkins.[16] San Francisco's City Engineer estimated the cost at $100 million (equivalent to $2.3 billion today), and impractical for the time. He asked bridge engineers whether it could be built for less.[10] One who responded, Joseph Strauss, was an ambitious engineer and poet who had, for his graduate thesis, designed a 55-mile-long (89 km) railroad bridge across the Bering Strait.[17] At the time, Strauss had completed some 400 drawbridges—most of which were inland—and nothing on the scale of the new project.[3] Strauss's initial drawings[16] were for a massive cantilever on each side of the strait, connected by a central suspension segment, which Strauss promised could be built for $17 million (equivalent to $391 million today).[10] Local authorities agreed to proceed only on the assurance that Strauss would alter the design and accept input from several consulting project experts.[citation needed] A suspension-bridge design was considered the most practical, because of recent advances in metallurgy.[10] Strauss spent more than a decade drumming up support in Northern California.[18] The bridge faced opposition, including litigation, from many sources. The Department of War was concerned that the bridge would interfere with ship traffic. The navy feared that a ship collision or sabotage to the bridge could block the entrance to one of its main harbors. Unions demanded guarantees that local workers would be favored for construction jobs. Southern Pacific Railroad, one of the most powerful business interests in California, opposed the bridge as competition to its ferry fleet and filed a lawsuit against the project, leading to a mass boycott of the ferry service.[10] In May 1924, Colonel Herbert Deakyne held the second hearing on the Bridge on behalf of the Secretary of War in a request to use federal land for construction. Deakyne, on behalf of the Secretary of War, approved the transfer of land needed for the bridge structure and leading roads to the "Bridging the Golden Gate Association" and both San Francisco County and Marin County, pending further bridge plans by Strauss.[19] Another ally was the fledgling automobile industry, which supported the development of roads and bridges to increase demand for automobiles.[13] The bridge's name was first used when the project was initially discussed in 1917 by M.M. O'Shaughnessy, city engineer of San Francisco, and Strauss. The name became official with the passage of the Golden Gate Bridge and Highway District Act by the state legislature in 1923, creating a special district to design, build and finance the bridge.[20] San Francisco and most of the counties along the North Coast of California joined the Golden Gate Bridge District, with the exception being Humboldt County, whose residents opposed the bridge's construction and the traffic it would generate.[21]


Source: https://en.wikipedia.org/wiki/Golden_Gate_Bridge

Colosseum

The Colosseum was used to host gladiatorial shows as well as a variety of other events. The shows, called munera, were always given by private individuals rather than the state. They had a strong religious element but were also demonstrations of power and family prestige, and were immensely popular with the population. Another popular type of show was the animal hunt, or venatio. This utilized a great variety of wild beasts, mainly imported from Africa and the Middle East, and included creatures such as rhinoceros, hippopotamuses, elephants, giraffes, aurochs, wisents, Barbary lions, panthers, leopards, bears, Caspian tigers, crocodiles and ostriches. Battles and hunts were often staged amid elaborate sets with movable trees and buildings. Such events were occasionally on a huge scale; Trajan is said to have celebrated his victories in Dacia in 107 with contests involving 11,000 animals and 10,000 gladiators over the course of 123 days. During lunch intervals, executions ad bestias would be staged. Those condemned to death would be sent into the arena, naked and unarmed, to face the beasts of death which would literally tear them to pieces. Other performances would also take place by acrobats and magicians, typically during the intervals. During the early days of the Colosseum, ancient writers recorded that the building was used for naumachiae (more properly known as navalia proelia) or simulated sea battles. Accounts of the inaugural games held by Titus in AD 80 describe it being filled with water for a display of specially trained swimming horses and bulls. There is also an account of a re-enactment of a famous sea battle between the Corcyrean (Corfiot) Greeks and the Corinthians. This has been the subject of some debate among historians; although providing the water would not have been a problem, it is unclear how the arena could have been waterproofed, nor would there have been enough space in the arena for the warships to move around. It has been suggested that the reports either have the location wrong, or that the Colosseum originally featured a wide floodable channel down its central axis (which would later have been replaced by the hypogeum).[16] Sylvae or recreations of natural scenes were also held in the arena. Painters, technicians and architects would construct a simulation of a forest with real trees and bushes planted in the arena's floor, and animals would then be introduced. Such scenes might be used simply to display a natural environment for the urban population, or could otherwise be used as the backdrop for hunts or dramas depicting episodes from mythology. They were also occasionally used for executions in which the hero of the story – played by a condemned person – was killed in one of various gruesome but mythologically authentic ways, such as being mauled by beasts or burned to death.

Source: https://en.wikipedia.org/wiki/Colosseum

Leaning Tower of Piza

Galileo Galilei is said to have dropped two cannonballs of different masses from the tower to demonstrate that their speed of descent was independent of their mass. However, the only primary source for this is the biography Racconto istorico della vita di Galileo Galilei (Historical Account of the Life of Galileo Galilei), written by Galileo's secretary Vincenzo Viviani and published in 1717, long after Viviani's death.[18][19] During World War II, the Allies suspected that the Germans were using the tower as an observation post. A U.S. Army sergeant sent to confirm the presence of German troops in the tower was impressed by the beauty of the cathedral and its campanile, and thus refrained from ordering an artillery strike, sparing it from destruction.[20][21] Numerous efforts have been made to restore the tower to a vertical orientation or at least keep it from falling over. Most of these efforts failed; some worsened the tilt. On February 27, 1964, the government of Italy requested aid in preventing the tower from toppling. It was, however, considered important to retain the current tilt, due to the role that this element played in promoting the tourism industry of Pisa.[22] A multinational task force of engineers, mathematicians, and historians gathered on the Azores islands to discuss stabilisation methods. It was found that the tilt was increasing in combination with the softer foundations on the lower side. Many methods were proposed to stabilise the tower, including the addition of 800 tonnes of lead counterweights to the raised end of the base.[23] The tower and the neighbouring cathedral, baptistery, and cemetery are included in the Piazza del Duomo UNESCO World Heritage Site, which was declared in 1987.[24] The tower was closed to the public on January 7, 1990, after more than two decades of stabilisation studies and spurred by the abrupt collapse of the Civic Tower of Pavia in 1989. The bells were removed to relieve some weight, and cables were cinched around the third level and anchored several hundred meters away. Apartments and houses in the path of the tower were vacated for safety. The solution chosen to prevent the collapse of the tower was to slightly straighten it to a safer angle by removing 38 cubic metres (1,342 cubic feet) of soil from underneath the raised end. The tower was straightened by 45 centimetres (17.7 inches), returning to its 1838 position. After a decade of corrective reconstruction and stabilization efforts, the tower was reopened to the public on December 15, 2001 and was declared stable for at least another 300 years.[23] In total, 70 metric tons (77 short tons) of earth were removed.[25] In May 2008, engineers announced that the tower had been stabilized such that it had stopped moving for the first time in its history. They stated that it would be stable for at least 200 years.[25]

Source: https://en.wikipedia.org/wiki/Leaning_Tower_of_Pisa

Pompeii

The period between about 450–375 BC witnessed large areas of the city being abandoned while important sanctuaries such as the Temple of Apollo show a sudden lack of votive material remains.[20] The Samnites, people coming from the areas of Abruzzo and Molise, and allies of the Romans, conquered Greek Cumae between 423 and 420 BC and it is likely that in advance, all the surrounding territory, including Pompeii, was conquered around 424 BC. The new rulers gradually imposed their architecture and enlarged the town. From 343 BC the first Roman army entered the Campanian plain bringing with it the customs and traditions of Rome and in the Roman war against the Latins the Samnites were faithful to Rome. Pompeii, although governed by the Samnites, entered in effect in the Roman orbit, to which it remained faithful even during the third Samnite war and in the war against Pyrrhus. The city walls were reinforced in Sarno stone in the early 3rd century BC (the Limestone enceinte, or the first Samnite wall). It formed the basis for the currently visible walls with an outer wall of rectangular limestone blocks as an enormous terrace wall supporting a large agger, or earth embankment, behind it. After the Samnite Wars from 290 BC, Pompeii was forced to accept the status of socii of Rome, maintaining, however, linguistic and administrative autonomy. From the outbreak of the Second Punic War (218–201 BC) in which Pompeii remained faithful to Rome, an additional internal retaining wall was built and the agger and outer façade raised resulting in a double parapet with wider wall-walk.[21] Despite the political uncertainty of these events and the progressive migration of wealthy men to quieter cities in the eastern Mediterranean, Pompeii continued to flourish due to the production and trade of wine and oil with places like Provence and Spain,[22] as well as to intensive agriculture on farms around the city. In the 2nd century BC, Pompeii enriched itself by taking part in Rome's conquest of the east as shown by a statue of Apollo in the Forum erected by Lucius Mummius in gratitude for their support in the sack of Corinth and the eastern campaigns. These riches enabled Pompeii to bloom and expand to its ultimate limits. The forum and many public and private buildings of high architectural quality were built, including the large theatre, the sanctuary to Jupiter, the Basilica, the Comitium, the Stabian baths and a new two-story portico.[23]

Source: https://en.wikipedia.org/wiki/Pompeii